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Improve /proc/interrupts further

PATCH Superseded Thomas Gleixner 3 participants 23 messages Mar 31

Subsystems (11)

v4 of 6 Superseded Latest is v6 →

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Thomas Gleixner

author maintainer
#0 lore raw

v4 cover Improve /proc/interrupts further

This is a follow up to v3 which can be found here:

https://lore.kernel.org/[email protected]

The v1 cover letter contains a full analysis, explanation and numbers:

https://lore.kernel.org/[email protected]

TLDR:

- The performance of reading of /proc/interrupts has been improved piecewise over the years, but most of the low hanging fruit has been left on the table.

Changes vs. V2:

- Reworked the NMI interrupt cleanup to be RT compatible. That was noticed when trying to address the next point.

- Made per CPU and NMI type teardown update the valid for proc condition

- Fixed the brainfart of writing to __ro_after_init memory by seperating the decision to emit a particular counter out into a simple bitmap and making the descriptor table const.

- Updated the GDB script changes to the bitmap mechanism and removed the stale ERR/MIS prints which are not longer required.

- Made irq_stat_init() a late initcall so it's guaranteed that the platform IPI and the posted MSI mechanisms have been initialized

- Add the AMD/HYGON deferred MCE vector to the conditionals and omit it from emission when running on a CPU from other vendors

Delta patch against v3 is below.

The series applies on top of v7.0-rc3 and is also available via git:

git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git irq-proc-v4

Thanks,

tglx
---

arch/x86/include/asm/irq.h +0 -2
index 25d22e33e58c..194dfff84cb1 100644
@@ -47,6 +47,4 @@ void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif
 
-void irq_init_stats(void);
-
 #endif /* _ASM_X86_IRQ_H */
arch/x86/kernel/irq.c +20 -11
index 0b3723cec0b9..de1c35fa5e75 100644
@@ -76,7 +76,7 @@ struct irq_stat_info {
 #define IDS(idx, sym, txt) [IRQ_COUNT_##idx] =				\
 	{ .skip_vector = DEFAULT_SUPPRESSED_VECTOR, .symbol = sym, .text = txt }
 
-static struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] __ro_after_init = {
+static const struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] = {
 	ISS(NMI,			"NMI", "  Non-maskable interrupts\n"),
 #ifdef CONFIG_X86_LOCAL_APIC
 	ISS(APIC_TIMER,			"LOC", "  Local timer interrupts\n"),
@@ -128,26 +128,36 @@ static struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] __ro_after_init = {
 #endif
 };
 
-void __init irq_init_stats(void)
+static DECLARE_BITMAP(irq_stat_count_show, IRQ_COUNT_MAX) __read_mostly;
+
+static int __init irq_init_stats(void)
 {
-	struct irq_stat_info *info = irq_stat_info;
+	const struct irq_stat_info *info = irq_stat_info;
 
 	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
-		if (info->skip_vector && info->skip_vector != DEFAULT_SUPPRESSED_VECTOR &&
-		    test_bit(info->skip_vector, system_vectors))
-			info->skip_vector = 0;
+		if (!info->skip_vector || (info->skip_vector != DEFAULT_SUPPRESSED_VECTOR &&
+					   test_bit(info->skip_vector, system_vectors)))
+			set_bit(i, irq_stat_count_show);
 	}
 
 #ifdef CONFIG_X86_LOCAL_APIC
 	if (!x86_platform_ipi_callback)
-		irq_stat_info[IRQ_COUNT_X86_PLATFORM_IPI].skip_vector = 1;
+		clear_bit(IRQ_COUNT_X86_PLATFORM_IPI, irq_stat_count_show);
 #endif
 
 #ifdef CONFIG_X86_POSTED_MSI
 	if (!posted_msi_enabled())
-		irq_stat_info[IRQ_COUNT_POSTED_MSI_NOTIFICATION].skip_vector = 1;
+		clear_bit(IRQ_COUNT_POSTED_MSI_NOTIFICATION, irq_stat_count_show);
+#endif
+
+#ifdef CONFIG_X86_MCE_AMD
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
+	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
+		clear_bit(IRQ_COUNT_DEFERRED_ERROR, irq_stat_count_show);
 #endif
+	return 0;
 }
+late_initcall(irq_init_stats);
 
 /*
  * Used for default enabled counters to increment the stats and to enable the
@@ -156,8 +166,7 @@ void __init irq_init_stats(void)
 void irq_stat_inc_and_enable(enum irq_stat_counts which)
 {
 	this_cpu_inc(irq_stat.counts[which]);
-	/* Pairs with the READ_ONCE() in arch_show_interrupts() */
-	WRITE_ONCE(irq_stat_info[which].skip_vector, 0);
+	set_bit(which, irq_stat_count_show);
 }
 
 #ifdef CONFIG_PROC_FS
@@ -169,7 +178,7 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	const struct irq_stat_info *info = irq_stat_info;
 
 	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
-		if (READ_ONCE(info->skip_vector))
+		if (!test_bit(i, irq_stat_count_show))
 			continue;
 
 		seq_printf(p, "%*s:", prec, info->symbol);
arch/x86/kernel/irqinit.c +0 -2
index 325c0ad8fb9c..6ab9eac64670 100644
@@ -104,8 +104,6 @@ void __init native_init_IRQ(void)
 	if (!cpu_feature_enabled(X86_FEATURE_FRED))
 		idt_setup_apic_and_irq_gates();
 
-	irq_init_stats();
-
 	lapic_assign_system_vectors();
 
 	if (!acpi_ioapic && !of_ioapic && nr_legacy_irqs()) {
kernel/irq/manage.c +27 -17

86 lines not on this page · raw message

scripts/gdb/linux/interrupts.py +4 -15
index 6ca7e32f35b0..418f3ece2f0f 100644
@@ -90,13 +90,6 @@ def show_irq_desc(prec, chip_width, irq):
 
     return text
 
-def show_irq_err_count(prec):
-    cnt = utils.gdb_eval_or_none("irq_err_count")
-    text = ""
-    if cnt is not None:
-        text += "%*s: %10u\n" % (prec, "ERR", cnt['counter'])
-    return text
-
 def x86_show_irqstat(prec, pfx, idx, desc):
     irq_stat = gdb.parse_and_eval("&irq_stat.counts[%d]" %idx)
     text = "%*s: " % (prec, pfx)
@@ -109,22 +102,18 @@ def x86_show_irqstat(prec, pfx, idx, desc):
 def x86_show_interupts(prec):
     info_type = gdb.lookup_type('struct irq_stat_info')
     info = gdb.parse_and_eval('irq_stat_info')
+    bitmap = gdb.parse_and_eval('irq_stat_count_show')
+    nbits = 8 * int(bitmap.type.sizeof)
 
     text = ""
     for idx in range(int(info.type.sizeof / info_type.sizeof)):
-        if info[idx]['skip_vector']:
+        show = bitmap[idx / nbits]
+        if not show & 1 << (idx % nbits):
             continue
         pfx = info[idx]['symbol'].string()
         desc = info[idx]['text'].string()
         text += x86_show_irqstat(prec, pfx, idx, desc)
 
-    text += show_irq_err_count(prec)
-
-    if constants.LX_CONFIG_X86_IO_APIC:
-        cnt = utils.gdb_eval_or_none("irq_mis_count")
-        if cnt is not None:
-            text += "%*s: %10u\n" % (prec, "MIS", cnt['counter'])
-
     return text
 
 def arm_common_show_interrupts(prec):
author maintainer
#1 lore raw

PATCH v4 1/15 x86/irq: Optimize interrupts decimals printing

From: Dmitry Ilvokhin <[email protected]>

Monitoring tools periodically scan /proc/interrupts to export metrics as a timeseries for future analysis and investigation.

In large fleets, /proc/interrupts is polled (often every few seconds) on every machine. The cumulative overhead adds up quickly across thousands of nodes, so reducing the cost of generating these stats does have a measurable operational impact. With the ongoing trend toward higher core counts per machine, this cost becomes even more noticeable over time, since interrupt counters are per-CPU. In Meta's fleet, we have observed this overhead at scale.

Although a binary /proc interface would be a better long-term solution due to lower formatting (kernel side) and parsing (userspace side) overhead, the text interface will remain in use for some time, even if better solutions will be available. Optimizing the /proc/interrupts printing code is therefore still beneficial.

Function seq_printf() supports rich format string for decimals printing, but it doesn't required for printing /proc/interrupts per CPU counters, seq_put_decimal_ull_width() function can be used instead to print per CPU counters, because very limited formatting is required for this case. Similar optimization idea is already used in show_interrupts().

As a side effect this aligns the x86 decriptions with the generic interrupts event descriptions.

Performance counter stats (truncated) for 'sh -c cat /proc/interrupts

Before:

      3.42 msec task-clock        #    0.802 CPUs utilized   ( +-  0.05% )
         1      context-switches  #  291.991 /sec            ( +-  0.74% )
         0      cpu-migrations    #    0.000 /sec
       343      page-faults       #  100.153 K/sec           ( +-  0.01% )
 8,932,242      instructions      #    1.66  insn per cycle  ( +-  0.34% )
 5,374,427      cycles            #    1.569 GHz             ( +-  0.04% )
 1,483,154      branches          #  433.068 M/sec           ( +-  0.22% )
    28,768      branch-misses     #    1.94% of all branches ( +-  0.31% )

0.00427182 +- 0.00000215 seconds time elapsed ( +- 0.05% )

After:

      2.39 msec task-clock        #    0.796 CPUs utilized   ( +-  0.06% )
         1      context-switches  #  418.541 /sec            ( +-  0.70% )
         0      cpu-migrations    #    0.000 /sec
       343      page-faults       #  143.560 K/sec           ( +-  0.01% )
 7,020,982      instructions      #    1.30  insn per cycle  ( +-  0.52% )
 5,397,266      cycles            #    2.259 GHz             ( +-  0.06% )
 1,569,648      branches          #  656.962 M/sec           ( +-  0.08% )
    25,419      branch-misses     #    1.62% of all branches ( +-  0.72% )

0.00299996 +- 0.00000206 seconds time elapsed ( +- 0.07% )

Relative speed up in time elapsed is around 29%.

[ tglx: Fixed it up so it applies to current mainline ]

---
Changes v2:
- Expanded commit message: add more rationale for the proposed change.
- Renamed helper put_spaced_decimal() -> put_decimal() primarely to make checkpatch.pl --strict pass.

 arch/x86/kernel/irq.c |  112 ++++++++++++++++++++++++++------------------------
 1 file changed, 59 insertions(+), 53 deletions(-)
arch/x86/kernel/irq.c +59 -53
@@ -62,6 +62,18 @@ void ack_bad_irq(unsigned int irq)
 	apic_eoi();
 }
 
+/*
+ * A helper routine for putting space and decimal number without overhead
+ * from rich format of printf().
+ */
+static void put_decimal(struct seq_file *p, unsigned long long num)
+{
+	const char *delimiter = " ";
+	unsigned int width = 10;
+
+	seq_put_decimal_ull_width(p, delimiter, num, width);
+}
+
 #define irq_stats(x)		(&per_cpu(irq_stat, x))
 /*
  * /proc/interrupts printing for arch specific interrupts
@@ -70,103 +82,101 @@ int arch_show_interrupts(struct seq_file
 {
 	int j;
 
-	seq_printf(p, "%*s: ", prec, "NMI");
+	seq_printf(p, "%*s:", prec, "NMI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->__nmi_count);
+		put_decimal(p, irq_stats(j)->__nmi_count);
 	seq_puts(p, "  Non-maskable interrupts\n");
 #ifdef CONFIG_X86_LOCAL_APIC
-	seq_printf(p, "%*s: ", prec, "LOC");
+	seq_printf(p, "%*s:", prec, "LOC");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->apic_timer_irqs);
+		put_decimal(p, irq_stats(j)->apic_timer_irqs);
 	seq_puts(p, "  Local timer interrupts\n");
 
-	seq_printf(p, "%*s: ", prec, "SPU");
+	seq_printf(p, "%*s:", prec, "SPU");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_spurious_count);
+		put_decimal(p, irq_stats(j)->irq_spurious_count);
 	seq_puts(p, "  Spurious interrupts\n");
-	seq_printf(p, "%*s: ", prec, "PMI");
+	seq_printf(p, "%*s:", prec, "PMI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->apic_perf_irqs);
+		put_decimal(p, irq_stats(j)->apic_perf_irqs);
 	seq_puts(p, "  Performance monitoring interrupts\n");
-	seq_printf(p, "%*s: ", prec, "IWI");
+	seq_printf(p, "%*s:", prec, "IWI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->apic_irq_work_irqs);
+		put_decimal(p, irq_stats(j)->apic_irq_work_irqs);
 	seq_puts(p, "  IRQ work interrupts\n");
-	seq_printf(p, "%*s: ", prec, "RTR");
+	seq_printf(p, "%*s:", prec, "RTR");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->icr_read_retry_count);
+		put_decimal(p, irq_stats(j)->icr_read_retry_count);
 	seq_puts(p, "  APIC ICR read retries\n");
 	if (x86_platform_ipi_callback) {
-		seq_printf(p, "%*s: ", prec, "PLT");
+		seq_printf(p, "%*s:", prec, "PLT");
 		for_each_online_cpu(j)
-			seq_printf(p, "%10u ", irq_stats(j)->x86_platform_ipis);
+			put_decimal(p, irq_stats(j)->x86_platform_ipis);
 		seq_puts(p, "  Platform interrupts\n");
 	}
 #endif
 #ifdef CONFIG_SMP
-	seq_printf(p, "%*s: ", prec, "RES");
+	seq_printf(p, "%*s:", prec, "RES");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_resched_count);
+		put_decimal(p, irq_stats(j)->irq_resched_count);
 	seq_puts(p, "  Rescheduling interrupts\n");
-	seq_printf(p, "%*s: ", prec, "CAL");
+	seq_printf(p, "%*s:", prec, "CAL");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_call_count);
+		put_decimal(p, irq_stats(j)->irq_call_count);
 	seq_puts(p, "  Function call interrupts\n");
-	seq_printf(p, "%*s: ", prec, "TLB");
+	seq_printf(p, "%*s:", prec, "TLB");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_tlb_count);
+		put_decimal(p, irq_stats(j)->irq_tlb_count);
 	seq_puts(p, "  TLB shootdowns\n");
 #endif
 #ifdef CONFIG_X86_THERMAL_VECTOR
-	seq_printf(p, "%*s: ", prec, "TRM");
+	seq_printf(p, "%*s:", prec, "TRM");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_thermal_count);
+		put_decimal(p, irq_stats(j)->irq_thermal_count);
 	seq_puts(p, "  Thermal event interrupts\n");
 #endif
 #ifdef CONFIG_X86_MCE_THRESHOLD
-	seq_printf(p, "%*s: ", prec, "THR");
+	seq_printf(p, "%*s:", prec, "THR");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_threshold_count);
+		put_decimal(p, irq_stats(j)->irq_threshold_count);
 	seq_puts(p, "  Threshold APIC interrupts\n");
 #endif
 #ifdef CONFIG_X86_MCE_AMD
-	seq_printf(p, "%*s: ", prec, "DFR");
+	seq_printf(p, "%*s:", prec, "DFR");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_deferred_error_count);
+		put_decimal(p, irq_stats(j)->irq_deferred_error_count);
 	seq_puts(p, "  Deferred Error APIC interrupts\n");
 #endif
 #ifdef CONFIG_X86_MCE
-	seq_printf(p, "%*s: ", prec, "MCE");
+	seq_printf(p, "%*s:", prec, "MCE");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(mce_exception_count, j));
+		put_decimal(p, per_cpu(mce_exception_count, j));
 	seq_puts(p, "  Machine check exceptions\n");
-	seq_printf(p, "%*s: ", prec, "MCP");
+	seq_printf(p, "%*s:", prec, "MCP");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(mce_poll_count, j));
+		put_decimal(p, per_cpu(mce_poll_count, j));
 	seq_puts(p, "  Machine check polls\n");
 #endif
 #ifdef CONFIG_X86_HV_CALLBACK_VECTOR
 	if (test_bit(HYPERVISOR_CALLBACK_VECTOR, system_vectors)) {
-		seq_printf(p, "%*s: ", prec, "HYP");
+		seq_printf(p, "%*s:", prec, "HYP");
 		for_each_online_cpu(j)
-			seq_printf(p, "%10u ",
-				   irq_stats(j)->irq_hv_callback_count);
+			put_decimal(p, irq_stats(j)->irq_hv_callback_count);
 		seq_puts(p, "  Hypervisor callback interrupts\n");
 	}
 #endif
 #if IS_ENABLED(CONFIG_HYPERV)
 	if (test_bit(HYPERV_REENLIGHTENMENT_VECTOR, system_vectors)) {
-		seq_printf(p, "%*s: ", prec, "HRE");
+		seq_printf(p, "%*s:", prec, "HRE");
 		for_each_online_cpu(j)
-			seq_printf(p, "%10u ",
-				   irq_stats(j)->irq_hv_reenlightenment_count);
+			put_decimal(p,
+				    irq_stats(j)->irq_hv_reenlightenment_count);
 		seq_puts(p, "  Hyper-V reenlightenment interrupts\n");
 	}
 	if (test_bit(HYPERV_STIMER0_VECTOR, system_vectors)) {
-		seq_printf(p, "%*s: ", prec, "HVS");
+		seq_printf(p, "%*s:", prec, "HVS");
 		for_each_online_cpu(j)
-			seq_printf(p, "%10u ",
-				   irq_stats(j)->hyperv_stimer0_count);
+			put_decimal(p, irq_stats(j)->hyperv_stimer0_count);
 		seq_puts(p, "  Hyper-V stimer0 interrupts\n");
 	}
 #endif
@@ -175,35 +185,31 @@ int arch_show_interrupts(struct seq_file
 	seq_printf(p, "%*s: %10u\n", prec, "MIS", atomic_read(&irq_mis_count));
 #endif
 #if IS_ENABLED(CONFIG_KVM)
-	seq_printf(p, "%*s: ", prec, "PIN");
+	seq_printf(p, "%*s:", prec, "PIN");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->kvm_posted_intr_ipis);
+		put_decimal(p, irq_stats(j)->kvm_posted_intr_ipis);
 	seq_puts(p, "  Posted-interrupt notification event\n");
 
-	seq_printf(p, "%*s: ", prec, "NPI");
+	seq_printf(p, "%*s:", prec, "NPI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ",
-			   irq_stats(j)->kvm_posted_intr_nested_ipis);
+		put_decimal(p, irq_stats(j)->kvm_posted_intr_nested_ipis);
 	seq_puts(p, "  Nested posted-interrupt event\n");
 
-	seq_printf(p, "%*s: ", prec, "PIW");
+	seq_printf(p, "%*s:", prec, "PIW");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ",
-			   irq_stats(j)->kvm_posted_intr_wakeup_ipis);
+		put_decimal(p, irq_stats(j)->kvm_posted_intr_wakeup_ipis);
 	seq_puts(p, "  Posted-interrupt wakeup event\n");
 #endif
 #ifdef CONFIG_GUEST_PERF_EVENTS
-	seq_printf(p, "%*s: ", prec, "VPMI");
+	seq_printf(p, "%*s:", prec, "VPMI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ",
-			   irq_stats(j)->perf_guest_mediated_pmis);
+		put_decimal(p, irq_stats(j)->perf_guest_mediated_pmis);
 	seq_puts(p, " Perf Guest Mediated PMI\n");
 #endif
 #ifdef CONFIG_X86_POSTED_MSI
-	seq_printf(p, "%*s: ", prec, "PMN");
+	seq_printf(p, "%*s:", prec, "PMN");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ",
-			   irq_stats(j)->posted_msi_notification_count);
+		put_decimal(p, irq_stats(j)->posted_msi_notification_count);
 	seq_puts(p, "  Posted MSI notification event\n");
 #endif
 	return 0;
author maintainer
#2 lore raw

PATCH v4 2/15 genirq/proc: Avoid formatting zero counts in /proc/interrupts

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

A large portion of interrupt count entries are zero. There is no point in formatting the zero value as it is way cheeper to just emit a constant string.

Collect the number of consecutive zero counts and emit them in one go before a non-zero count and at the end of the line.

---
V2: Use sizeof() for ZSTR1_LEN - Dmitry

---
 include/linux/interrupt.h |    1 +
 kernel/irq/proc.c         |   42 +++++++++++++++++++++++++++++++++++++-----
 2 files changed, 38 insertions(+), 5 deletions(-)
include/linux/interrupt.h +1 -0
@@ -864,6 +864,7 @@ static inline void init_irq_proc(void)
 struct seq_file;
 int show_interrupts(struct seq_file *p, void *v);
 int arch_show_interrupts(struct seq_file *p, int prec);
+void irq_proc_emit_counts(struct seq_file *p, unsigned int __percpu *cnts);
 
 extern int early_irq_init(void);
 extern int arch_probe_nr_irqs(void);
kernel/irq/proc.c +37 -5

54 lines not on this page · raw message

author maintainer
#3 lore raw

PATCH v4 3/15 genirq/proc: Utilize irq_desc::tot_count to avoid evaluation

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Interrupts which are not marked per CPU increment not only the per CPU statistics, but also the accumulation counter irq_desc::tot_count.

Change the counter to type unsigned long so it does not produce sporadic zeros due to wrap arounds on 64-bit machines and do a quick check for non per CPU interrupts. If the counter is zero, then simply emit a full set of zero strings. That spares the evaluation of the per CPU counters completely for interrupts with zero events.

---
 include/linux/irqdesc.h |    6 +++---
 kernel/irq/proc.c       |   11 ++++++++++-
 2 files changed, 13 insertions(+), 4 deletions(-)
include/linux/irqdesc.h +3 -3
@@ -52,8 +52,8 @@ struct irq_redirect {
  * @depth:		disable-depth, for nested irq_disable() calls
  * @wake_depth:		enable depth, for multiple irq_set_irq_wake() callers
  * @tot_count:		stats field for non-percpu irqs
- * @irq_count:		stats field to detect stalled irqs
  * @last_unhandled:	aging timer for unhandled count
+ * @irq_count:		stats field to detect stalled irqs
  * @irqs_unhandled:	stats field for spurious unhandled interrupts
  * @threads_handled:	stats field for deferred spurious detection of threaded handlers
  * @threads_handled_last: comparator field for deferred spurious detection of threaded handlers
@@ -87,9 +87,9 @@ struct irq_desc {
 	unsigned int		core_internal_state__do_not_mess_with_it;
 	unsigned int		depth;		/* nested irq disables */
 	unsigned int		wake_depth;	/* nested wake enables */
-	unsigned int		tot_count;
-	unsigned int		irq_count;	/* For detecting broken IRQs */
+	unsigned long		tot_count;
 	unsigned long		last_unhandled;	/* Aging timer for unhandled count */
+	unsigned int		irq_count;	/* For detecting broken IRQs */
 	unsigned int		irqs_unhandled;
 	atomic_t		threads_handled;
 	int			threads_handled_last;
kernel/irq/proc.c +10 -1
@@ -521,7 +521,16 @@ int show_interrupts(struct seq_file *p,
 		return 0;
 
 	seq_printf(p, "%*d:", prec, i);
-	irq_proc_emit_counts(p, &desc->kstat_irqs->cnt);
+
+	/*
+	 * Always output per CPU interrupts. Output device interrupts only when
+	 * desc::tot_count is not zero.
+	 */
+	if (irq_settings_is_per_cpu(desc) || irq_settings_is_per_cpu_devid(desc) ||
+	    data_race(desc->tot_count))
+		irq_proc_emit_counts(p, &desc->kstat_irqs->cnt);
+	else
+		irq_proc_emit_zero_counts(p, num_online_cpus());
 	seq_putc(p, ' ');
 
 	guard(raw_spinlock_irq)(&desc->lock);
author maintainer
#4 lore raw

PATCH v4 4/15 x86/irq: Make irqstats array based

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Having the x86 specific interrupt statistics as a data structure with individual members instead of an array is just stupid as it requires endless copy and paste in arch_show_interrupts() and arch_irq_stat_cpu(), where the latter does not even take the latest interrupt additions into account. The resulting #ifdef orgy is just disgusting.

Convert it to an array of counters, which does not make a difference in the actual interrupt hotpath increment as the array index is constant and therefore not any different than the member based access.

But in arch_show_interrupts() and arch_irq_stat_cpu() this just turns into a loop, which reduces the text size by ~2k (~12%):

   text	   data	    bss	    dec	    hex	filename
  19643	  15250	    904	  35797	   8bd5	../build/arch/x86/kernel/irq.o
  17355	  15250	    904	  33509	   82e5	../build/arch/x86/kernel/irq.o

Adding a new vector or software counter only requires to update the table and everything just works. Using the core provided emit function which speeds up 0 outputs makes it significantly faster.

---
V4: Make irq_stats_init() a late initcall so that platform IPI and posted
vector initialization has been done
Supress AMD/HYGON specific vectors when CPU is from a different vendor

V3: Add the missing #ifdeffery - 0-day
Add the alignment back - Radu
Address dyslexia for real - Michael

V2: Simplified and extended vector skip mechanism
Fixup the typoes - Micheal, Dmitry
Added the lost precision back for ERR/MIS - Dmitry

---
 arch/x86/events/amd/core.c          |    2 
 arch/x86/events/amd/ibs.c           |    2 
 arch/x86/events/core.c              |    2 
 arch/x86/events/intel/core.c        |    2 
 arch/x86/events/intel/knc.c         |    2 
 arch/x86/events/intel/p4.c          |    2 
 arch/x86/events/zhaoxin/core.c      |    2 
 arch/x86/hyperv/hv_init.c           |    2 
 arch/x86/include/asm/hardirq.h      |   77 ++++++----
 arch/x86/include/asm/mce.h          |    3 
 arch/x86/kernel/apic/apic.c         |    4 
 arch/x86/kernel/apic/ipi.c          |    2 
 arch/x86/kernel/cpu/acrn.c          |    2 
 arch/x86/kernel/cpu/mce/amd.c       |    2 
 arch/x86/kernel/cpu/mce/core.c      |    8 -
 arch/x86/kernel/cpu/mce/threshold.c |    2 
 arch/x86/kernel/cpu/mshyperv.c      |    4 
 arch/x86/kernel/irq.c               |  269 ++++++++++++++----------------------
 arch/x86/kernel/irq_work.c          |    2 
 arch/x86/kernel/kvm.c               |    2 
 arch/x86/kernel/nmi.c               |    4 
 arch/x86/kernel/smp.c               |    6 
 arch/x86/mm/tlb.c                   |    2 
 arch/x86/xen/enlighten_hvm.c        |    2 
 arch/x86/xen/enlighten_pv.c         |    2 
 arch/x86/xen/smp.c                  |    6 
 arch/x86/xen/smp_pv.c               |    2 
 27 files changed, 184 insertions(+), 233 deletions(-)
arch/x86/events/amd/core.c +1 -1
@@ -1032,7 +1032,7 @@ static int amd_pmu_v2_handle_irq(struct
 	 * Unmasking the LVTPC is not required as the Mask (M) bit of the LVT
 	 * PMI entry is not set by the local APIC when a PMC overflow occurs
 	 */
-	inc_irq_stat(apic_perf_irqs);
+	inc_perf_irq_stat();
 
 done:
 	cpuc->enabled = pmu_enabled;
arch/x86/events/amd/ibs.c +1 -1
@@ -1403,7 +1403,7 @@ perf_ibs_nmi_handler(unsigned int cmd, s
 	handled += perf_ibs_handle_irq(&perf_ibs_op, regs);
 
 	if (handled)
-		inc_irq_stat(apic_perf_irqs);
+		inc_perf_irq_stat();
 
 	perf_sample_event_took(sched_clock() - stamp);
 
arch/x86/events/core.c +1 -1
@@ -1747,7 +1747,7 @@ int x86_pmu_handle_irq(struct pt_regs *r
 	}
 
 	if (handled)
-		inc_irq_stat(apic_perf_irqs);
+		inc_perf_irq_stat();
 
 	return handled;
 }
arch/x86/events/intel/core.c +1 -1
@@ -3504,7 +3504,7 @@ static int handle_pmi_common(struct pt_r
 	int bit;
 	int handled = 0;
 
-	inc_irq_stat(apic_perf_irqs);
+	inc_perf_irq_stat();
 
 	/*
 	 * Ignore a range of extra bits in status that do not indicate
arch/x86/events/intel/knc.c +1 -1
@@ -238,7 +238,7 @@ static int knc_pmu_handle_irq(struct pt_
 		goto done;
 	}
 
-	inc_irq_stat(apic_perf_irqs);
+	inc_perf_irq_stat();
 
 	for_each_set_bit(bit, (unsigned long *)&status, X86_PMC_IDX_MAX) {
 		struct perf_event *event = cpuc->events[bit];
arch/x86/events/intel/p4.c +1 -1
@@ -1077,7 +1077,7 @@ static int p4_pmu_handle_irq(struct pt_r
 	}
 
 	if (handled)
-		inc_irq_stat(apic_perf_irqs);
+		inc_perf_irq_stat();
 
 	/*
 	 * When dealing with the unmasking of the LVTPC on P4 perf hw, it has
arch/x86/events/zhaoxin/core.c +1 -1
@@ -373,7 +373,7 @@ static int zhaoxin_pmu_handle_irq(struct
 	else
 		zhaoxin_pmu_ack_status(status);
 
-	inc_irq_stat(apic_perf_irqs);
+	inc_perf_irq_stat();
 
 	/*
 	 * CondChgd bit 63 doesn't mean any overflow status. Ignore
arch/x86/hyperv/hv_init.c +1 -1
@@ -219,7 +219,7 @@ static inline bool hv_reenlightenment_av
 DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_reenlightenment)
 {
 	apic_eoi();
-	inc_irq_stat(irq_hv_reenlightenment_count);
+	inc_irq_stat(HYPERV_REENLIGHTENMENT);
 	schedule_delayed_work(&hv_reenlightenment_work, HZ/10);
 }
 
arch/x86/include/asm/hardirq.h +47 -30

113 lines not on this page · raw message

arch/x86/include/asm/mce.h +0 -3
@@ -291,9 +291,6 @@ bool mce_is_memory_error(struct mce *m);
 bool mce_is_correctable(struct mce *m);
 bool mce_usable_address(struct mce *m);
 
-DECLARE_PER_CPU(unsigned, mce_exception_count);
-DECLARE_PER_CPU(unsigned, mce_poll_count);
-
 typedef DECLARE_BITMAP(mce_banks_t, MAX_NR_BANKS);
 DECLARE_PER_CPU(mce_banks_t, mce_poll_banks);
 
arch/x86/kernel/apic/apic.c +2 -2
@@ -1040,7 +1040,7 @@ static void local_apic_timer_interrupt(v
 	/*
 	 * the NMI deadlock-detector uses this.
 	 */
-	inc_irq_stat(apic_timer_irqs);
+	inc_irq_stat(APIC_TIMER);
 
 	evt->event_handler(evt);
 }
@@ -2108,7 +2108,7 @@ static noinline void handle_spurious_int
 
 	trace_spurious_apic_entry(vector);
 
-	inc_irq_stat(irq_spurious_count);
+	inc_irq_stat(SPURIOUS);
 
 	/*
 	 * If this is a spurious interrupt then do not acknowledge
arch/x86/kernel/apic/ipi.c +1 -1
@@ -120,7 +120,7 @@ u32 apic_mem_wait_icr_idle_timeout(void)
 	for (cnt = 0; cnt < 1000; cnt++) {
 		if (!(apic_read(APIC_ICR) & APIC_ICR_BUSY))
 			return 0;
-		inc_irq_stat(icr_read_retry_count);
+		inc_irq_stat(ICR_READ_RETRY);
 		udelay(100);
 	}
 	return APIC_ICR_BUSY;
arch/x86/kernel/cpu/acrn.c +1 -1
@@ -52,7 +52,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_acrn_hv_ca
 	 * HYPERVISOR_CALLBACK_VECTOR.
 	 */
 	apic_eoi();
-	inc_irq_stat(irq_hv_callback_count);
+	inc_irq_stat(HYPERVISOR_CALLBACK);
 
 	if (acrn_intr_handler)
 		acrn_intr_handler();
arch/x86/kernel/cpu/mce/amd.c +1 -1
@@ -840,7 +840,7 @@ bool amd_mce_usable_address(struct mce *
 DEFINE_IDTENTRY_SYSVEC(sysvec_deferred_error)
 {
 	trace_deferred_error_apic_entry(DEFERRED_ERROR_VECTOR);
-	inc_irq_stat(irq_deferred_error_count);
+	inc_irq_stat(DEFERRED_ERROR);
 	deferred_error_int_vector();
 	trace_deferred_error_apic_exit(DEFERRED_ERROR_VECTOR);
 	apic_eoi();
arch/x86/kernel/cpu/mce/core.c +2 -6
@@ -67,8 +67,6 @@ static DEFINE_MUTEX(mce_sysfs_mutex);
 
 #define SPINUNIT		100	/* 100ns */
 
-DEFINE_PER_CPU(unsigned, mce_exception_count);
-
 DEFINE_PER_CPU_READ_MOSTLY(unsigned int, mce_num_banks);
 
 DEFINE_PER_CPU_READ_MOSTLY(struct mce_bank[MAX_NR_BANKS], mce_banks_array);
@@ -716,8 +714,6 @@ static noinstr void mce_read_aux(struct
 	}
 }
 
-DEFINE_PER_CPU(unsigned, mce_poll_count);
-
 /*
  * We have three scenarios for checking for Deferred errors:
  *
@@ -820,7 +816,7 @@ void machine_check_poll(enum mcp_flags f
 	struct mce *m;
 	int i;
 
-	this_cpu_inc(mce_poll_count);
+	inc_irq_stat(MCE_POLL);
 
 	mce_gather_info(&err, NULL);
 	m = &err.m;
@@ -1595,7 +1591,7 @@ noinstr void do_machine_check(struct pt_
 	 */
 	lmce = 1;
 
-	this_cpu_inc(mce_exception_count);
+	inc_irq_stat(MCE_EXCEPTION);
 
 	mce_gather_info(&err, regs);
 	m = &err.m;
arch/x86/kernel/cpu/mce/threshold.c +1 -1
@@ -37,7 +37,7 @@ void (*mce_threshold_vector)(void) = def
 DEFINE_IDTENTRY_SYSVEC(sysvec_threshold)
 {
 	trace_threshold_apic_entry(THRESHOLD_APIC_VECTOR);
-	inc_irq_stat(irq_threshold_count);
+	inc_irq_stat(THRESHOLD_APIC);
 	mce_threshold_vector();
 	trace_threshold_apic_exit(THRESHOLD_APIC_VECTOR);
 	apic_eoi();
arch/x86/kernel/cpu/mshyperv.c +2 -2
@@ -154,7 +154,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_cal
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 
-	inc_irq_stat(irq_hv_callback_count);
+	inc_irq_stat(HYPERVISOR_CALLBACK);
 	if (mshv_handler)
 		mshv_handler();
 
@@ -191,7 +191,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_sti
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 
-	inc_irq_stat(hyperv_stimer0_count);
+	inc_irq_stat(HYPERV_STIMER0);
 	if (hv_stimer0_handler)
 		hv_stimer0_handler();
 	add_interrupt_randomness(HYPERV_STIMER0_VECTOR);
arch/x86/kernel/irq.c +105 -164

361 lines not on this page · raw message

arch/x86/kernel/irq_work.c +1 -1
@@ -18,7 +18,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_irq_work)
 {
 	apic_eoi();
 	trace_irq_work_entry(IRQ_WORK_VECTOR);
-	inc_irq_stat(apic_irq_work_irqs);
+	inc_irq_stat(IRQ_WORK);
 	irq_work_run();
 	trace_irq_work_exit(IRQ_WORK_VECTOR);
 }
arch/x86/kernel/kvm.c +1 -1
@@ -310,7 +310,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_kvm_asyncp
 
 	apic_eoi();
 
-	inc_irq_stat(irq_hv_callback_count);
+	inc_irq_stat(HYPERVISOR_CALLBACK);
 
 	if (__this_cpu_read(async_pf_enabled)) {
 		token = __this_cpu_read(apf_reason.token);
arch/x86/kernel/nmi.c +2 -2
@@ -576,7 +576,7 @@ DEFINE_IDTENTRY_RAW(exc_nmi)
 
 	irq_state = irqentry_nmi_enter(regs);
 
-	inc_irq_stat(__nmi_count);
+	inc_irq_stat(NMI);
 
 	if (IS_ENABLED(CONFIG_NMI_CHECK_CPU) && ignore_nmis) {
 		WRITE_ONCE(nsp->idt_ignored, nsp->idt_ignored + 1);
@@ -725,7 +725,7 @@ DEFINE_FREDENTRY_NMI(exc_nmi)
 
 	irq_state = irqentry_nmi_enter(regs);
 
-	inc_irq_stat(__nmi_count);
+	inc_irq_stat(NMI);
 	default_do_nmi(regs);
 
 	irqentry_nmi_exit(regs, irq_state);
arch/x86/kernel/smp.c +3 -3
@@ -249,7 +249,7 @@ DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_res
 {
 	apic_eoi();
 	trace_reschedule_entry(RESCHEDULE_VECTOR);
-	inc_irq_stat(irq_resched_count);
+	inc_irq_stat(RESCHEDULE);
 	scheduler_ipi();
 	trace_reschedule_exit(RESCHEDULE_VECTOR);
 }
@@ -258,7 +258,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_call_funct
 {
 	apic_eoi();
 	trace_call_function_entry(CALL_FUNCTION_VECTOR);
-	inc_irq_stat(irq_call_count);
+	inc_irq_stat(CALL_FUNCTION);
 	generic_smp_call_function_interrupt();
 	trace_call_function_exit(CALL_FUNCTION_VECTOR);
 }
@@ -267,7 +267,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_call_funct
 {
 	apic_eoi();
 	trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR);
-	inc_irq_stat(irq_call_count);
+	inc_irq_stat(CALL_FUNCTION);
 	generic_smp_call_function_single_interrupt();
 	trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);
 }
arch/x86/mm/tlb.c +1 -1
@@ -1144,7 +1144,7 @@ static void flush_tlb_func(void *info)
 	VM_WARN_ON(!irqs_disabled());
 
 	if (!local) {
-		inc_irq_stat(irq_tlb_count);
+		inc_irq_stat(TLB);
 		count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
 	}
 
arch/x86/xen/enlighten_hvm.c +1 -1
@@ -125,7 +125,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_xen_hvm_ca
 	if (xen_percpu_upcall)
 		apic_eoi();
 
-	inc_irq_stat(irq_hv_callback_count);
+	inc_irq_stat(HYPERVISOR_CALLBACK);
 
 	xen_evtchn_do_upcall();
 
arch/x86/xen/enlighten_pv.c +1 -1
@@ -728,7 +728,7 @@ static void __xen_pv_evtchn_do_upcall(st
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 
-	inc_irq_stat(irq_hv_callback_count);
+	inc_irq_stat(HYPERVISOR_CALLBACK);
 
 	xen_evtchn_do_upcall();
 
arch/x86/xen/smp.c +3 -3
@@ -23,7 +23,7 @@ static irqreturn_t xen_call_function_sin
  */
 static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
 {
-	inc_irq_stat(irq_resched_count);
+	inc_irq_stat(RESCHEDULE);
 	scheduler_ipi();
 
 	return IRQ_HANDLED;
@@ -254,7 +254,7 @@ void xen_send_IPI_allbutself(int vector)
 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
 {
 	generic_smp_call_function_interrupt();
-	inc_irq_stat(irq_call_count);
+	inc_irq_stat(CALL_FUNCTION);
 
 	return IRQ_HANDLED;
 }
@@ -262,7 +262,7 @@ static irqreturn_t xen_call_function_int
 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
 {
 	generic_smp_call_function_single_interrupt();
-	inc_irq_stat(irq_call_count);
+	inc_irq_stat(CALL_FUNCTION);
 
 	return IRQ_HANDLED;
 }
arch/x86/xen/smp_pv.c +1 -1
@@ -400,7 +400,7 @@ static void xen_pv_stop_other_cpus(int w
 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 {
 	irq_work_run();
-	inc_irq_stat(apic_irq_work_irqs);
+	inc_irq_stat(IRQ_WORK);
 
 	return IRQ_HANDLED;
 }
author maintainer
#5 lore raw

Re: [patch V4 04/15] x86/irq: Make irqstats array based

Quoted 13 lines · Thomas Gleixner
arch/x86/kernel/irq.c +13 -0
+static int __init irq_init_stats(void)
+{
+	struct irq_stat_info *info = irq_stat_info;
+
+	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
+		if (info->skip_vector && test_bit(info->skip_vector, system_vectors))
+			info->skip_vector = 0;
+	}
+
+#ifdef CONFIG_X86_LOCAL_APIC
+	if (!x86_platform_ipi_callback)
+		irq_stat_info[IRQ_COUNT_X86_PLATFORM_IPI].skip_vector = 1;
+#endif

arch/x86/kernel/irq.c void ack_bad_irq(unsigned int irq) · line 146

Quoted 10 lines
arch/x86/kernel/irq.c +10 -0
+
+#ifdef CONFIG_X86_POSTED_MSI
+	if (!posted_msi_enabled())
+		irq_stat_info[IRQ_COUNT_POSTED_MSI_NOTIFICATION].skip_vector = 1;
+#endif
+
+#ifdef CONFIG_X86_MCE_AMD
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
+	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
+		irq_stat_info[IRQ_COUNT_DEFERRED_VECTOR].skip_vector = 1;

Grmbl. IRQ_COUNT_DEFERRED_ERROR. The next patch fixes it but ....

Quoted 4 lines
arch/x86/kernel/irq.c +4 -0
+#endif
+	return 0;
+}
+late_initcall(irq_init_stats);

arch/x86/kernel/irq.c void ack_bad_irq(unsigned int irq) · line 160

Quoted 10 lines
arch/x86/kernel/irq.c +10 -0
+
+/*
+ * Used for default enabled counters to increment the stats and to enable the
+ * entry for /proc/interrupts output.
+ */
+void irq_stat_inc_and_enable(enum irq_stat_counts which)
+{
+	this_cpu_inc(irq_stat.counts[which]);
+	set_bit(which, irq_stat_count_show);
+}

Also this one needs to be in the next patch.

author maintainer
#6 lore raw

PATCH v4 5/15 x86/irq: Suppress unlikely interrupt stats by default

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Unlikely interrupt counters like the spurious vector and the synthetic APIC ICR read retry show up in /proc/interrupts with all counts 0 most of the time.

As these are events which should never happen, suppress them by default and enable them for output when they actually happen.

This requires a seperate bitmap as the description array is marked __ro_after_init. With that bitmap in place it becomes RO data.

---
V4: Fix the bad idea of writing to __ro_after_init marked data
V3: New patch

---
 arch/x86/include/asm/hardirq.h |    1 +
 arch/x86/kernel/apic/apic.c    |    2 +-
 arch/x86/kernel/apic/ipi.c     |    2 +-
 arch/x86/kernel/irq.c          |   28 ++++++++++++++++++----------
 4 files changed, 21 insertions(+), 12 deletions(-)
arch/x86/include/asm/hardirq.h +1 -0
@@ -68,6 +68,7 @@ DECLARE_PER_CPU_ALIGNED(struct pi_desc,
 #define __ARCH_IRQ_STAT
 
 #define inc_irq_stat(index)	this_cpu_inc(irq_stat.counts[IRQ_COUNT_##index])
+void irq_stat_inc_and_enable(enum irq_stat_counts which);
 
 #ifdef CONFIG_X86_LOCAL_APIC
 #define inc_perf_irq_stat()	inc_irq_stat(APIC_PERF)
arch/x86/kernel/apic/apic.c +1 -1
@@ -2108,7 +2108,7 @@ static noinline void handle_spurious_int
 
 	trace_spurious_apic_entry(vector);
 
-	inc_irq_stat(SPURIOUS);
+	irq_stat_inc_and_enable(IRQ_COUNT_SPURIOUS);
 
 	/*
 	 * If this is a spurious interrupt then do not acknowledge
arch/x86/kernel/apic/ipi.c +1 -1
@@ -120,7 +120,7 @@ u32 apic_mem_wait_icr_idle_timeout(void)
 	for (cnt = 0; cnt < 1000; cnt++) {
 		if (!(apic_read(APIC_ICR) & APIC_ICR_BUSY))
 			return 0;
-		inc_irq_stat(ICR_READ_RETRY);
+		irq_stat_inc_and_enable(IRQ_COUNT_ICR_READ_RETRY);
 		udelay(100);
 	}
 	return APIC_ICR_BUSY;
arch/x86/kernel/irq.c +18 -10
@@ -68,19 +68,24 @@ struct irq_stat_info {
 	const char	*text;
 };
 
+#define DEFAULT_SUPPRESSED_VECTOR	UINT_MAX
+
 #define ISS(idx, sym, txt) [IRQ_COUNT_##idx] = { .symbol = sym, .text = txt }
 
 #define ITS(idx, sym, txt) [IRQ_COUNT_##idx] =				\
 	{ .skip_vector = idx## _VECTOR, .symbol = sym, .text = txt }
 
-static struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] __ro_after_init = {
+#define IDS(idx, sym, txt) [IRQ_COUNT_##idx] =				\
+	{ .skip_vector = DEFAULT_SUPPRESSED_VECTOR, .symbol = sym, .text = txt }
+
+static const struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] = {
 	ISS(NMI,			"NMI", "  Non-maskable interrupts\n"),
 #ifdef CONFIG_X86_LOCAL_APIC
 	ISS(APIC_TIMER,			"LOC", "  Local timer interrupts\n"),
-	ISS(SPURIOUS,			"SPU", "  Spurious interrupts\n"),
+	IDS(SPURIOUS,			"SPU", "  Spurious interrupts\n"),
 	ISS(APIC_PERF,			"PMI", "  Performance monitoring interrupts\n"),
 	ISS(IRQ_WORK,			"IWI", "  IRQ work interrupts\n"),
-	ISS(ICR_READ_RETRY,		"RTR", "  APIC ICR read retries\n"),
+	IDS(ICR_READ_RETRY,		"RTR", "  APIC ICR read retries\n"),
 	ISS(X86_PLATFORM_IPI,		"PLT", "  Platform interrupts\n"),
 #endif
 #ifdef CONFIG_SMP
@@ -121,29 +126,32 @@ static struct irq_stat_info irq_stat_inf
 #endif
 };
 
+static DECLARE_BITMAP(irq_stat_count_show, IRQ_COUNT_MAX) __read_mostly;
+
 static int __init irq_init_stats(void)
 {
-	struct irq_stat_info *info = irq_stat_info;
+	const struct irq_stat_info *info = irq_stat_info;
 
 	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
-		if (info->skip_vector && test_bit(info->skip_vector, system_vectors))
-			info->skip_vector = 0;
+		if (!info->skip_vector || (info->skip_vector != DEFAULT_SUPPRESSED_VECTOR &&
+					   test_bit(info->skip_vector, system_vectors)))
+			set_bit(i, irq_stat_count_show);
 	}
 
 #ifdef CONFIG_X86_LOCAL_APIC
 	if (!x86_platform_ipi_callback)
-		irq_stat_info[IRQ_COUNT_X86_PLATFORM_IPI].skip_vector = 1;
+		clear_bit(IRQ_COUNT_X86_PLATFORM_IPI, irq_stat_count_show);
 #endif
 
 #ifdef CONFIG_X86_POSTED_MSI
 	if (!posted_msi_enabled())
-		irq_stat_info[IRQ_COUNT_POSTED_MSI_NOTIFICATION].skip_vector = 1;
+		clear_bit(IRQ_COUNT_POSTED_MSI_NOTIFICATION, irq_stat_count_show);
 #endif
 
 #ifdef CONFIG_X86_MCE_AMD
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
-		irq_stat_info[IRQ_COUNT_DEFERRED_VECTOR].skip_vector = 1;
+		clear_bit(IRQ_COUNT_DEFERRED_ERROR, irq_stat_count_show);
 #endif
 	return 0;
 }
@@ -168,7 +176,7 @@ int arch_show_interrupts(struct seq_file
 	const struct irq_stat_info *info = irq_stat_info;
 
 	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
-		if (info->skip_vector)
+		if (!test_bit(i, irq_stat_count_show))
 			continue;
 
 		seq_printf(p, "%*s:", prec, info->symbol);
reviewer Reviewed-by on v4 5/15
#7 lore raw

Re: [patch V4 05/15] x86/irq: Suppress unlikely interrupt stats by default

Quoted 26 lines · Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Unlikely interrupt counters like the spurious vector and the synthetic APIC ICR read retry show up in /proc/interrupts with all counts 0 most of the time.

As these are events which should never happen, suppress them by default and enable them for output when they actually happen.

This requires a seperate bitmap as the description array is marked __ro_after_init. With that bitmap in place it becomes RO data.

---
V4: Fix the bad idea of writing to __ro_after_init marked data
V3: New patch
---
 arch/x86/include/asm/hardirq.h |    1 + arch/x86/kernel/apic/apic.c    |    2 +- arch/x86/kernel/apic/ipi.c     |    2 +- arch/x86/kernel/irq.c          |   28 ++++++++++++++++++----------

 4 files changed, 21 insertions(+), 12 deletions(-)
arch/x86/include/asm/hardirq.h +0 -0
@@ -68,6 +68,7 @@ DECLARE_PER_CPU_ALIGNED(struct pi_desc,
  #define __ARCH_IRQ_STAT
Quoted 3 lines


 #define inc_irq_stat(index) this_cpu_inc(irq_stat.counts[IRQ_COUNT_##index])
+void irq_stat_inc_and_enable(enum irq_stat_counts which);

This is just a matter of style but for symmetry with inc_irq_stat(), I would prepend '__' to the function name and create a wrapper macro that adds the 'IRQ_COUNT_' prefix.

And for consistency (you also have inc_perf_irq_stat()) I would call it inc_and_enable_irq_stat().

And yes, my comments above are totally bike shedding :)

Quoted 99 lines

 #ifdef CONFIG_X86_LOCAL_APIC
 #define inc_perf_irq_stat() inc_irq_stat(APIC_PERF)

arch/x86/kernel/apic/apic.c +0 -0
@@ -2108,7 +2108,7 @@ static noinline void handle_spurious_int


  trace_spurious_apic_entry(vector);

arch/x86/kernel/apic/apic.c +1 -1
-	inc_irq_stat(SPURIOUS);
+	irq_stat_inc_and_enable(IRQ_COUNT_SPURIOUS);


  /*
  * If this is a spurious interrupt then do not acknowledge

arch/x86/kernel/apic/ipi.c +1 -1
@@ -120,7 +120,7 @@ u32 apic_mem_wait_icr_idle_timeout(void)
  	for (cnt = 0; cnt < 1000; cnt++) {
  		if (!(apic_read(APIC_ICR) & APIC_ICR_BUSY))
  			return 0;
-		inc_irq_stat(ICR_READ_RETRY);
+		irq_stat_inc_and_enable(IRQ_COUNT_ICR_READ_RETRY);
  		udelay(100);
  	}
  	return APIC_ICR_BUSY;
arch/x86/kernel/irq.c +0 -0
@@ -68,19 +68,24 @@ struct irq_stat_info {
  	const char	*text;
  };

arch/x86/kernel/irq.c +2 -0
+#define DEFAULT_SUPPRESSED_VECTOR	UINT_MAX
+

 #define ISS(idx, sym, txt) [IRQ_COUNT_##idx] = { .symbol = sym, .text = txt }
 #define ITS(idx, sym, txt) [IRQ_COUNT_##idx] = \
  { .skip_vector = idx## _VECTOR, .symbol = sym, .text = txt }

arch/x86/kernel/irq.c +4 -1
-static struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] __ro_after_init = {
+#define IDS(idx, sym, txt) [IRQ_COUNT_##idx] =				\
+	{ .skip_vector = DEFAULT_SUPPRESSED_VECTOR, .symbol = sym, .text = txt }
+
+static const struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] = {

  ISS(NMI, "NMI", "  Non-maskable interrupts\n"),
 #ifdef CONFIG_X86_LOCAL_APIC
  ISS(APIC_TIMER, "LOC", "  Local timer interrupts\n"),

arch/x86/kernel/irq.c +1 -1
-	ISS(SPURIOUS,			"SPU", "  Spurious interrupts\n"),
+	IDS(SPURIOUS,			"SPU", "  Spurious interrupts\n"),

  ISS(APIC_PERF, "PMI", "  Performance monitoring interrupts\n"),
  ISS(IRQ_WORK, "IWI", "  IRQ work interrupts\n"),

arch/x86/kernel/irq.c +1 -1
-	ISS(ICR_READ_RETRY,		"RTR", "  APIC ICR read retries\n"),
+	IDS(ICR_READ_RETRY,		"RTR", "  APIC ICR read retries\n"),

  ISS(X86_PLATFORM_IPI, "PLT", "  Platform interrupts\n"),
 #endif
 #ifdef CONFIG_SMP

arch/x86/kernel/irq.c +0 -0
@@ -121,29 +126,32 @@ static struct irq_stat_info irq_stat_inf
  #endif
  };

arch/x86/kernel/irq.c +2 -0
+static DECLARE_BITMAP(irq_stat_count_show, IRQ_COUNT_MAX) __read_mostly;
+

 static int __init irq_init_stats(void)
 {

arch/x86/kernel/irq.c +1 -1
-	struct irq_stat_info *info = irq_stat_info;
+	const struct irq_stat_info *info = irq_stat_info;


  for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {

arch/x86/kernel/irq.c +3 -2
-		if (info->skip_vector && test_bit(info->skip_vector, system_vectors))
-			info->skip_vector = 0;
+		if (!info->skip_vector || (info->skip_vector != DEFAULT_SUPPRESSED_VECTOR &&
+					   test_bit(info->skip_vector, system_vectors)))
+			set_bit(i, irq_stat_count_show);

  }

 #ifdef CONFIG_X86_LOCAL_APIC
  if (!x86_platform_ipi_callback)

arch/x86/kernel/irq.c +1 -1
-		irq_stat_info[IRQ_COUNT_X86_PLATFORM_IPI].skip_vector = 1;
+		clear_bit(IRQ_COUNT_X86_PLATFORM_IPI, irq_stat_count_show);

 #endif

 #ifdef CONFIG_X86_POSTED_MSI
  if (!posted_msi_enabled())

arch/x86/kernel/irq.c +1 -1
-		irq_stat_info[IRQ_COUNT_POSTED_MSI_NOTIFICATION].skip_vector = 1;
+		clear_bit(IRQ_COUNT_POSTED_MSI_NOTIFICATION, irq_stat_count_show);

 #endif

 #ifdef CONFIG_X86_MCE_AMD
  if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)

arch/x86/kernel/irq.c +1 -1
-		irq_stat_info[IRQ_COUNT_DEFERRED_VECTOR].skip_vector = 1;
+		clear_bit(IRQ_COUNT_DEFERRED_ERROR, irq_stat_count_show);

 #endif
  return 0;
 }

arch/x86/kernel/irq.c +0 -0
@@ -168,7 +176,7 @@ int arch_show_interrupts(struct seq_file
  	const struct irq_stat_info *info = irq_stat_info;


  for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {

arch/x86/kernel/irq.c +1 -1
-		if (info->skip_vector)
+		if (!test_bit(i, irq_stat_count_show))
Quoted 3 lines

  continue;

  seq_printf(p, "%*s:", prec, info->symbol);

author maintainer
#8 lore raw

PATCH v4 6/15 x86/irq: Move IOAPIC misrouted and PIC/APIC error counts into irq_stats

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

The special treatment of these counts is just adding extra code for no real value. The irq_stats mechanism allows to suppress output of counters, which should never happen by default and provides a mechanism to enable them for the rare case that they occur.

Move the IOAPIC misrouted and the PIC/APIC error counts into irq_stats, mark them suppressed by default and update the sites which increment them.

This changes the output format of 'ERR' and 'MIS' in case there are events to the regular per CPU display format and otherwise suppresses them completely.

As a side effect this removes the arch_cpu_stat() mechanism from proc/stat which was only there to account for the error interrupts on x86 and missed to take the misrouted ones into account.

---
V3: New patch

---
 arch/x86/include/asm/hardirq.h |    7 ++++---
 arch/x86/include/asm/hw_irq.h  |    4 ----
 arch/x86/kernel/apic/apic.c    |    2 +-
 arch/x86/kernel/apic/io_apic.c |    4 +---
 arch/x86/kernel/i8259.c        |    2 +-
 arch/x86/kernel/irq.c          |   16 ++++------------
 fs/proc/stat.c                 |    4 ----
 7 files changed, 11 insertions(+), 28 deletions(-)
arch/x86/include/asm/hardirq.h +4 -3
@@ -50,6 +50,10 @@ enum irq_stat_counts {
 #ifdef CONFIG_X86_POSTED_MSI
 	IRQ_COUNT_POSTED_MSI_NOTIFICATION,
 #endif
+	IRQ_COUNT_PIC_APIC_ERROR,
+#ifdef CONFIG_X86_IO_APIC
+	IRQ_COUNT_IOAPIC_MISROUTED,
+#endif
 	IRQ_COUNT_MAX,
 };
 
@@ -81,9 +85,6 @@ extern void ack_bad_irq(unsigned int irq
 #ifdef CONFIG_PROC_FS
 extern u64 arch_irq_stat_cpu(unsigned int cpu);
 #define arch_irq_stat_cpu	arch_irq_stat_cpu
-
-extern u64 arch_irq_stat(void);
-#define arch_irq_stat		arch_irq_stat
 #endif
 
 DECLARE_PER_CPU_CACHE_HOT(u16, __softirq_pending);
arch/x86/include/asm/hw_irq.h +0 -4
@@ -110,10 +110,6 @@ static inline void lock_vector_lock(void
 static inline void unlock_vector_lock(void) {}
 #endif
 
-/* Statistics */
-extern atomic_t irq_err_count;
-extern atomic_t irq_mis_count;
-
 extern void elcr_set_level_irq(unsigned int irq);
 
 extern char irq_entries_start[];
arch/x86/kernel/apic/apic.c +1 -1
@@ -2180,7 +2180,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_error_inte
 		apic_write(APIC_ESR, 0);
 	v = apic_read(APIC_ESR);
 	apic_eoi();
-	atomic_inc(&irq_err_count);
+	irq_stat_inc_and_enable(IRQ_COUNT_PIC_APIC_ERROR);
 
 	apic_pr_debug("APIC error on CPU%d: %02x", smp_processor_id(), v);
 
arch/x86/kernel/apic/io_apic.c +1 -3
@@ -1575,8 +1575,6 @@ static unsigned int startup_ioapic_irq(s
 	return was_pending;
 }
 
-atomic_t irq_mis_count;
-
 #ifdef CONFIG_GENERIC_PENDING_IRQ
 static bool io_apic_level_ack_pending(struct mp_chip_data *data)
 {
@@ -1713,7 +1711,7 @@ static void ioapic_ack_level(struct irq_
 	 * at the cpu.
 	 */
 	if (!(v & (1 << (i & 0x1f)))) {
-		atomic_inc(&irq_mis_count);
+		irq_stat_inc_and_enable(IRQ_COUNT_IOAPIC_MISROUTED);
 		eoi_ioapic_pin(cfg->vector, irq_data->chip_data);
 	}
 
arch/x86/kernel/i8259.c +1 -1
@@ -214,7 +214,7 @@ static void mask_and_ack_8259A(struct ir
 			       "spurious 8259A interrupt: IRQ%d.\n", irq);
 			spurious_irq_mask |= irqmask;
 		}
-		atomic_inc(&irq_err_count);
+		irq_stat_inc_and_enable(IRQ_COUNT_PIC_APIC_ERROR);
 		/*
 		 * Theoretically we do not have to handle this IRQ,
 		 * but in Linux this does not cause problems and is
arch/x86/kernel/irq.c +4 -12
@@ -39,8 +39,6 @@ EXPORT_PER_CPU_SYMBOL(__softirq_pending)
 
 DEFINE_PER_CPU_CACHE_HOT(struct irq_stack *, hardirq_stack_ptr);
 
-atomic_t irq_err_count;
-
 /*
  * 'what should we do if we get a hw irq event on an illegal vector'.
  * each architecture has to answer this themselves.
@@ -124,6 +122,10 @@ static const struct irq_stat_info irq_st
 #ifdef CONFIG_X86_POSTED_MSI
 	ISS(POSTED_MSI_NOTIFICATION,	"PMN", "  Posted MSI notification event\n"),
 #endif
+	IDS(PIC_APIC_ERROR,		"ERR", "  PIC/APIC error interrupts\n"),
+#ifdef CONFIG_X86_IO_APIC
+	IDS(IOAPIC_MISROUTED,		"MIS", "  Misrouted IO/APIC interrupts\n"),
+#endif
 };
 
 static DECLARE_BITMAP(irq_stat_count_show, IRQ_COUNT_MAX) __read_mostly;
@@ -183,10 +185,6 @@ int arch_show_interrupts(struct seq_file
 		irq_proc_emit_counts(p, &irq_stat.counts[i]);
 		seq_puts(p, info->text);
 	}
-
-	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
-	if (IS_ENABLED(CONFIG_X86_IO_APIC))
-		seq_printf(p, "%*s: %10u\n", prec, "MIS", atomic_read(&irq_mis_count));
 	return 0;
 }
 
@@ -202,12 +200,6 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
 		sum += p->counts[i];
 	return sum;
 }
-
-u64 arch_irq_stat(void)
-{
-	u64 sum = atomic_read(&irq_err_count);
-	return sum;
-}
 #endif /* CONFIG_PROC_FS */
 
 static __always_inline void handle_irq(struct irq_desc *desc,
fs/proc/stat.c +0 -4
@@ -18,9 +18,6 @@
 #ifndef arch_irq_stat_cpu
 #define arch_irq_stat_cpu(cpu) 0
 #endif
-#ifndef arch_irq_stat
-#define arch_irq_stat() 0
-#endif
 
 u64 get_idle_time(struct kernel_cpustat *kcs, int cpu)
 {
@@ -122,7 +119,6 @@ static int show_stat(struct seq_file *p,
 			sum_softirq += softirq_stat;
 		}
 	}
-	sum += arch_irq_stat();
 
 	seq_put_decimal_ull(p, "cpu  ", nsec_to_clock_t(user));
 	seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));
reviewer Reviewed-by on v4 6/15
#9 lore raw

Re: [patch V4 06/15] x86/irq: Move IOAPIC misrouted and PIC/APIC error counts into irq_stats

Quoted 171 lines · Thomas Gleixner

From: Thomas Gleixner <[email protected]>

The special treatment of these counts is just adding extra code for no real value. The irq_stats mechanism allows to suppress output of counters, which should never happen by default and provides a mechanism to enable them for the rare case that they occur.

Move the IOAPIC misrouted and the PIC/APIC error counts into irq_stats, mark them suppressed by default and update the sites which increment them.

This changes the output format of 'ERR' and 'MIS' in case there are events to the regular per CPU display format and otherwise suppresses them completely.

As a side effect this removes the arch_cpu_stat() mechanism from proc/stat which was only there to account for the error interrupts on x86 and missed to take the misrouted ones into account.

---
V3: New patch
---
 arch/x86/include/asm/hardirq.h |    7 ++++--- arch/x86/include/asm/hw_irq.h  |    4 ---- arch/x86/kernel/apic/apic.c    |    2 +- arch/x86/kernel/apic/io_apic.c |    4 +--- arch/x86/kernel/i8259.c        |    2 +- arch/x86/kernel/irq.c          |   16 ++++------------ fs/proc/stat.c                 |    4 ----

 7 files changed, 11 insertions(+), 28 deletions(-)
arch/x86/include/asm/hardirq.h +4 -0
@@ -50,6 +50,10 @@ enum irq_stat_counts {
  #ifdef CONFIG_X86_POSTED_MSI
  	IRQ_COUNT_POSTED_MSI_NOTIFICATION,
  #endif
+	IRQ_COUNT_PIC_APIC_ERROR,
+#ifdef CONFIG_X86_IO_APIC
+	IRQ_COUNT_IOAPIC_MISROUTED,
+#endif
  	IRQ_COUNT_MAX,
  };

arch/x86/include/asm/hardirq.h +0 -3
@@ -81,9 +85,6 @@ extern void ack_bad_irq(unsigned int irq
  #ifdef CONFIG_PROC_FS
  extern u64 arch_irq_stat_cpu(unsigned int cpu);
  #define arch_irq_stat_cpu	arch_irq_stat_cpu
-
-extern u64 arch_irq_stat(void);
-#define arch_irq_stat		arch_irq_stat
  #endif


 DECLARE_PER_CPU_CACHE_HOT(u16, __softirq_pending);

arch/x86/include/asm/hw_irq.h +0 -0
@@ -110,10 +110,6 @@ static inline void lock_vector_lock(void
  static inline void unlock_vector_lock(void) {}
  #endif

arch/x86/include/asm/hw_irq.h +0 -4
-/* Statistics */
-extern atomic_t irq_err_count;
-extern atomic_t irq_mis_count;
-

 extern void elcr_set_level_irq(unsigned int irq);
 extern char irq_entries_start[];

arch/x86/kernel/apic/apic.c +1 -1
@@ -2180,7 +2180,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_error_inte
  		apic_write(APIC_ESR, 0);
  	v = apic_read(APIC_ESR);
  	apic_eoi();
-	atomic_inc(&irq_err_count);
+	irq_stat_inc_and_enable(IRQ_COUNT_PIC_APIC_ERROR);


  apic_pr_debug("APIC error on CPU%d: %02x", smp_processor_id(), v);

arch/x86/kernel/apic/io_apic.c +0 -0
@@ -1575,8 +1575,6 @@ static unsigned int startup_ioapic_irq(s
  	return was_pending;
  }

arch/x86/kernel/apic/io_apic.c +0 -2
-atomic_t irq_mis_count;
-

 #ifdef CONFIG_GENERIC_PENDING_IRQ
 static bool io_apic_level_ack_pending(struct mp_chip_data *data) {

arch/x86/kernel/apic/io_apic.c +1 -1
@@ -1713,7 +1711,7 @@ static void ioapic_ack_level(struct irq_
  	 * at the cpu.
  	 */
  	if (!(v & (1 << (i & 0x1f)))) {
-		atomic_inc(&irq_mis_count);
+		irq_stat_inc_and_enable(IRQ_COUNT_IOAPIC_MISROUTED);
  		eoi_ioapic_pin(cfg->vector, irq_data->chip_data);
  	}

arch/x86/kernel/i8259.c +1 -1
@@ -214,7 +214,7 @@ static void mask_and_ack_8259A(struct ir
  			       "spurious 8259A interrupt: IRQ%d.\n", irq);
  			spurious_irq_mask |= irqmask;
  		}
-		atomic_inc(&irq_err_count);
+		irq_stat_inc_and_enable(IRQ_COUNT_PIC_APIC_ERROR);
  		/*
  		 * Theoretically we do not have to handle this IRQ,
  		 * but in Linux this does not cause problems and is
arch/x86/kernel/irq.c +0 -0
@@ -39,8 +39,6 @@ EXPORT_PER_CPU_SYMBOL(__softirq_pending)


 DEFINE_PER_CPU_CACHE_HOT(struct irq_stack *, hardirq_stack_ptr);

arch/x86/kernel/irq.c +0 -2
-atomic_t irq_err_count;
-

 /*
  * 'what should we do if we get a hw irq event on an illegal vector'.
  * each architecture has to answer this themselves.

arch/x86/kernel/irq.c +4 -0
@@ -124,6 +122,10 @@ static const struct irq_stat_info irq_st
  #ifdef CONFIG_X86_POSTED_MSI
  	ISS(POSTED_MSI_NOTIFICATION,	"PMN", "  Posted MSI notification event\n"),
  #endif
+	IDS(PIC_APIC_ERROR,		"ERR", "  PIC/APIC error interrupts\n"),
+#ifdef CONFIG_X86_IO_APIC
+	IDS(IOAPIC_MISROUTED,		"MIS", "  Misrouted IO/APIC interrupts\n"),
+#endif
  };


 static DECLARE_BITMAP(irq_stat_count_show, IRQ_COUNT_MAX) __read_mostly;

arch/x86/kernel/irq.c +0 -4
@@ -183,10 +185,6 @@ int arch_show_interrupts(struct seq_file
  		irq_proc_emit_counts(p, &irq_stat.counts[i]);
  		seq_puts(p, info->text);
  	}
-
-	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
-	if (IS_ENABLED(CONFIG_X86_IO_APIC))
-		seq_printf(p, "%*s: %10u\n", prec, "MIS", atomic_read(&irq_mis_count));
  	return 0;
  }

arch/x86/kernel/irq.c +0 -6
@@ -202,12 +200,6 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
  		sum += p->counts[i];
  	return sum;
  }
-
-u64 arch_irq_stat(void)
-{
-	u64 sum = atomic_read(&irq_err_count);
-	return sum;
-}
  #endif /* CONFIG_PROC_FS */


 static __always_inline void handle_irq(struct irq_desc *desc,

fs/proc/stat.c +0 -3
@@ -18,9 +18,6 @@
  #ifndef arch_irq_stat_cpu
  #define arch_irq_stat_cpu(cpu) 0
  #endif
-#ifndef arch_irq_stat
-#define arch_irq_stat() 0
-#endif


 u64 get_idle_time(struct kernel_cpustat *kcs, int cpu) {

fs/proc/stat.c +0 -1
@@ -122,7 +119,6 @@ static int show_stat(struct seq_file *p,
  			sum_softirq += softirq_stat;
  		}
  	}
-	sum += arch_irq_stat();
Quoted 3 lines


  seq_put_decimal_ull(p, "cpu  ", nsec_to_clock_t(user)); seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));

author maintainer
#10 lore raw

PATCH v4 7/15 scripts/gdb: Update x86 interrupts to the array based storage

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

x86 changed the interrupt statistics from a struct with individual members to an counter array. It also provides a corresponding info array with the strings for prefix and description and an indicator to skip the entry.

Update the already out of sync GDB script to use the counter and the info array, which keeps the GDB script in sync automatically.

---
V4: Adopted to irq_stat_count_show bitmap and removed the duplicate ERR/MIS output
V3: New patch - Radu

---
 scripts/gdb/linux/interrupts.py |   74 ++++++++--------------------------------
 1 file changed, 16 insertions(+), 58 deletions(-)
scripts/gdb/linux/interrupts.py +16 -58
@@ -90,71 +90,29 @@ irq_desc_type = utils.CachedType("struct
 
     return text
 
-def show_irq_err_count(prec):
-    cnt = utils.gdb_eval_or_none("irq_err_count")
-    text = ""
-    if cnt is not None:
-        text += "%*s: %10u\n" % (prec, "ERR", cnt['counter'])
-    return text
-
-def x86_show_irqstat(prec, pfx, field, desc):
-    irq_stat = gdb.parse_and_eval("&irq_stat")
+def x86_show_irqstat(prec, pfx, idx, desc):
+    irq_stat = gdb.parse_and_eval("&irq_stat.counts[%d]" %idx)
     text = "%*s: " % (prec, pfx)
     for cpu in cpus.each_online_cpu():
         stat = cpus.per_cpu(irq_stat, cpu)
-        text += "%10u " % (stat[field])
-    text += "  %s\n" % (desc)
-    return text
-
-def x86_show_mce(prec, var, pfx, desc):
-    pvar = gdb.parse_and_eval(var)
-    text = "%*s: " % (prec, pfx)
-    for cpu in cpus.each_online_cpu():
-        text += "%10u " % (cpus.per_cpu(pvar, cpu).dereference())
-    text += "  %s\n" % (desc)
+        text += "%10u " % (stat.dereference())
+    text += desc
     return text
 
 def x86_show_interupts(prec):
-    text = x86_show_irqstat(prec, "NMI", '__nmi_count', 'Non-maskable interrupts')
+    info_type = gdb.lookup_type('struct irq_stat_info')
+    info = gdb.parse_and_eval('irq_stat_info')
+    bitmap = gdb.parse_and_eval('irq_stat_count_show')
+    nbits = 8 * int(bitmap.type.sizeof)
 
-    if constants.LX_CONFIG_X86_LOCAL_APIC:
-        text += x86_show_irqstat(prec, "LOC", 'apic_timer_irqs', "Local timer interrupts")
-        text += x86_show_irqstat(prec, "SPU", 'irq_spurious_count', "Spurious interrupts")
-        text += x86_show_irqstat(prec, "PMI", 'apic_perf_irqs', "Performance monitoring interrupts")
-        text += x86_show_irqstat(prec, "IWI", 'apic_irq_work_irqs', "IRQ work interrupts")
-        text += x86_show_irqstat(prec, "RTR", 'icr_read_retry_count', "APIC ICR read retries")
-        if utils.gdb_eval_or_none("x86_platform_ipi_callback") is not None:
-            text += x86_show_irqstat(prec, "PLT", 'x86_platform_ipis', "Platform interrupts")
-
-    if constants.LX_CONFIG_SMP:
-        text += x86_show_irqstat(prec, "RES", 'irq_resched_count', "Rescheduling interrupts")
-        text += x86_show_irqstat(prec, "CAL", 'irq_call_count', "Function call interrupts")
-        text += x86_show_irqstat(prec, "TLB", 'irq_tlb_count', "TLB shootdowns")
-
-    if constants.LX_CONFIG_X86_THERMAL_VECTOR:
-        text += x86_show_irqstat(prec, "TRM", 'irq_thermal_count', "Thermal events interrupts")
-
-    if constants.LX_CONFIG_X86_MCE_THRESHOLD:
-        text += x86_show_irqstat(prec, "THR", 'irq_threshold_count', "Threshold APIC interrupts")
-
-    if constants.LX_CONFIG_X86_MCE_AMD:
-        text += x86_show_irqstat(prec, "DFR", 'irq_deferred_error_count', "Deferred Error APIC interrupts")
-
-    if constants.LX_CONFIG_X86_MCE:
-        text += x86_show_mce(prec, "&mce_exception_count", "MCE", "Machine check exceptions")
-        text += x86_show_mce(prec, "&mce_poll_count", "MCP", "Machine check polls")
-
-    text += show_irq_err_count(prec)
-
-    if constants.LX_CONFIG_X86_IO_APIC:
-        cnt = utils.gdb_eval_or_none("irq_mis_count")
-        if cnt is not None:
-            text += "%*s: %10u\n" % (prec, "MIS", cnt['counter'])
-
-    if constants.LX_CONFIG_KVM:
-        text += x86_show_irqstat(prec, "PIN", 'kvm_posted_intr_ipis', 'Posted-interrupt notification event')
-        text += x86_show_irqstat(prec, "NPI", 'kvm_posted_intr_nested_ipis', 'Nested posted-interrupt event')
-        text += x86_show_irqstat(prec, "PIW", 'kvm_posted_intr_wakeup_ipis', 'Posted-interrupt wakeup event')
+    text = ""
+    for idx in range(int(info.type.sizeof / info_type.sizeof)):
+        show = bitmap[idx / nbits]
+        if not show & 1 << (idx % nbits):
+            continue
+        pfx = info[idx]['symbol'].string()
+        desc = info[idx]['text'].string()
+        text += x86_show_irqstat(prec, pfx, idx, desc)
 
     return text
 
author maintainer
#11 lore raw

Re: [patch V4 07/15] scripts/gdb: Update x86 interrupts to the array based storage

scripts/gdb/linux/interrupts.py irq_desc_type = utils.CachedType("struct · line 98

Quoted 6 lines · Thomas Gleixner
scripts/gdb/linux/interrupts.py +0 -6
-def show_irq_err_count(prec):
-    cnt = utils.gdb_eval_or_none("irq_err_count")
-    text = ""
-    if cnt is not None:
-        text += "%*s: %10u\n" % (prec, "ERR", cnt['counter'])
-    return text

Just noticed that this is used by mips and needs to stay.

scripts/gdb/linux/interrupts.py irq_desc_type = utils.CachedType("struct · line 106

Quoted 6 lines

def x86_show_interupts(prec):

scripts/gdb/linux/interrupts.py +4 -1
-    text = x86_show_irqstat(prec, "NMI", '__nmi_count', 'Non-maskable interrupts')
+    info_type = gdb.lookup_type('struct irq_stat_info')
+    info = gdb.parse_and_eval('irq_stat_info')
+    bitmap = gdb.parse_and_eval('irq_stat_count_show')
+    nbits = 8 * int(bitmap.type.sizeof)

and this only works for a bitmap with size <= [32|64]. The correct variant is:

bitsperlong = 8 * int(bitmap.type.target().sizeof)

author maintainer
#12 lore raw

PATCH v4 8/15 genirq: Expose nr_irqs in core code

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

... to avoid function calls in the core code to retrieve the maximum number of interrupts.

Rename it to 'total_nr_irqs' as 'nr_irqs' is too generic and fix up the 'nr_irqs' reference in the related GDB script as well.

---
V3: Fix up the missing usage sites and gdb script - Radu

---
 kernel/irq/internals.h          |    1 +
 kernel/irq/irqdesc.c            |   28 ++++++++++++++--------------
 kernel/irq/proc.c               |    4 ++--
 scripts/gdb/linux/interrupts.py |    2 +-
 4 files changed, 18 insertions(+), 17 deletions(-)
kernel/irq/internals.h +1 -0
@@ -21,6 +21,7 @@
 
 extern bool noirqdebug;
 extern int irq_poll_cpu;
+extern unsigned int total_nr_irqs;
 
 extern struct irqaction chained_action;
 
kernel/irq/irqdesc.c +14 -14
@@ -140,14 +140,14 @@ static void desc_set_defaults(unsigned i
 	desc_smp_init(desc, node, affinity);
 }
 
-static unsigned int nr_irqs = NR_IRQS;
+unsigned int total_nr_irqs __read_mostly = NR_IRQS;
 
 /**
  * irq_get_nr_irqs() - Number of interrupts supported by the system.
  */
 unsigned int irq_get_nr_irqs(void)
 {
-	return nr_irqs;
+	return total_nr_irqs;
 }
 EXPORT_SYMBOL_GPL(irq_get_nr_irqs);
 
@@ -159,7 +159,7 @@ EXPORT_SYMBOL_GPL(irq_get_nr_irqs);
  */
 unsigned int irq_set_nr_irqs(unsigned int nr)
 {
-	nr_irqs = nr;
+	total_nr_irqs = nr;
 
 	return nr;
 }
@@ -187,9 +187,9 @@ static unsigned int irq_find_at_or_after
 	struct irq_desc *desc;
 
 	guard(rcu)();
-	desc = mt_find(&sparse_irqs, &index, nr_irqs);
+	desc = mt_find(&sparse_irqs, &index, total_nr_irqs);
 
-	return desc ? irq_desc_get_irq(desc) : nr_irqs;
+	return desc ? irq_desc_get_irq(desc) : total_nr_irqs;
 }
 
 static void irq_insert_desc(unsigned int irq, struct irq_desc *desc)
@@ -543,7 +543,7 @@ static bool irq_expand_nr_irqs(unsigned
 {
 	if (nr > MAX_SPARSE_IRQS)
 		return false;
-	nr_irqs = nr;
+	total_nr_irqs = nr;
 	return true;
 }
 
@@ -557,16 +557,16 @@ int __init early_irq_init(void)
 	/* Let arch update nr_irqs and return the nr of preallocated irqs */
 	initcnt = arch_probe_nr_irqs();
 	printk(KERN_INFO "NR_IRQS: %d, nr_irqs: %d, preallocated irqs: %d\n",
-	       NR_IRQS, nr_irqs, initcnt);
+	       NR_IRQS, total_nr_irqs, initcnt);
 
-	if (WARN_ON(nr_irqs > MAX_SPARSE_IRQS))
-		nr_irqs = MAX_SPARSE_IRQS;
+	if (WARN_ON(total_nr_irqs > MAX_SPARSE_IRQS))
+		total_nr_irqs = MAX_SPARSE_IRQS;
 
 	if (WARN_ON(initcnt > MAX_SPARSE_IRQS))
 		initcnt = MAX_SPARSE_IRQS;
 
-	if (initcnt > nr_irqs)
-		nr_irqs = initcnt;
+	if (initcnt > total_nr_irqs)
+		total_nr_irqs = initcnt;
 
 	for (i = 0; i < initcnt; i++) {
 		desc = alloc_desc(i, node, 0, NULL, NULL);
@@ -862,7 +862,7 @@ void irq_free_descs(unsigned int from, u
 {
 	int i;
 
-	if (from >= nr_irqs || (from + cnt) > nr_irqs)
+	if (from >= total_nr_irqs || (from + cnt) > total_nr_irqs)
 		return;
 
 	guard(mutex)(&sparse_irq_lock);
@@ -911,7 +911,7 @@ int __ref __irq_alloc_descs(int irq, uns
 	if (irq >=0 && start != irq)
 		return -EEXIST;
 
-	if (start + cnt > nr_irqs) {
+	if (start + cnt > total_nr_irqs) {
 		if (!irq_expand_nr_irqs(start + cnt))
 			return -ENOMEM;
 	}
@@ -923,7 +923,7 @@ EXPORT_SYMBOL_GPL(__irq_alloc_descs);
  * irq_get_next_irq - get next allocated irq number
  * @offset:	where to start the search
  *
- * Returns next irq number after offset or nr_irqs if none is found.
+ * Returns next irq number after offset or total_nr_irqs if none is found.
  */
 unsigned int irq_get_next_irq(unsigned int offset)
 {
kernel/irq/proc.c +2 -2
@@ -447,7 +447,7 @@ int __weak arch_show_interrupts(struct s
 }
 
 #ifndef ACTUAL_NR_IRQS
-# define ACTUAL_NR_IRQS irq_get_nr_irqs()
+# define ACTUAL_NR_IRQS total_nr_irqs
 #endif
 
 #define ZSTR1 "          0"
@@ -488,7 +488,7 @@ void irq_proc_emit_counts(struct seq_fil
 
 int show_interrupts(struct seq_file *p, void *v)
 {
-	const unsigned int nr_irqs = irq_get_nr_irqs();
+	const unsigned int nr_irqs = total_nr_irqs;
 	static int prec;
 
 	int i = *(loff_t *) v, j;
scripts/gdb/linux/interrupts.py +1 -1
@@ -174,7 +174,7 @@ irq_desc_type = utils.CachedType("struct
         super(LxInterruptList, self).__init__("lx-interruptlist", gdb.COMMAND_DATA)
 
     def invoke(self, arg, from_tty):
-        nr_irqs = gdb.parse_and_eval("nr_irqs")
+        nr_irqs = gdb.parse_and_eval("total_nr_irqs")
         prec = 3
         j = 1000
         while prec < 10 and j <= nr_irqs:
author maintainer
#13 lore raw

PATCH v4 9/15 genirq/manage: Make NMI cleanup RT safe

In reply to Thomas Gleixner

Eventually blocking functions cannot be invoked with interrupts disabled and a raw spin lock held. Restructure the code so this happens outside of the descriptor lock held region.

---
V4: New patch. Found when adding the validation update to it

---
 kernel/irq/manage.c |   37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)
kernel/irq/manage.c +21 -16
@@ -2026,24 +2026,30 @@ const void *free_irq(unsigned int irq, v
 }
 EXPORT_SYMBOL(free_irq);
 
-/* This function must be called with desc->lock held */
 static const void *__cleanup_nmi(unsigned int irq, struct irq_desc *desc)
 {
+	struct irqaction *action = NULL;
 	const char *devname = NULL;
 
-	desc->istate &= ~IRQS_NMI;
+	scoped_guard(raw_spinlock_irqsave, &desc->lock) {
+		irq_nmi_teardown(desc);
 
-	if (!WARN_ON(desc->action == NULL)) {
-		irq_pm_remove_action(desc, desc->action);
-		devname = desc->action->name;
-		unregister_handler_proc(irq, desc->action);
+		desc->istate &= ~IRQS_NMI;
 
-		kfree(desc->action);
+		if (!WARN_ON(desc->action == NULL)) {
+			action = desc->action;
+			irq_pm_remove_action(desc, action);
+			devname = action->name;
+		}
 		desc->action = NULL;
+
+		irq_settings_clr_disable_unlazy(desc);
+		irq_shutdown_and_deactivate(desc);
 	}
 
-	irq_settings_clr_disable_unlazy(desc);
-	irq_shutdown_and_deactivate(desc);
+	if (action)
+		unregister_handler_proc(irq, action);
+	kfree(action);
 
 	irq_release_resources(desc);
 
@@ -2067,8 +2073,6 @@ const void *free_nmi(unsigned int irq, v
 	if (WARN_ON(desc->depth == 0))
 		disable_nmi_nosync(irq);
 
-	guard(raw_spinlock_irqsave)(&desc->lock);
-	irq_nmi_teardown(desc);
 	return __cleanup_nmi(irq, desc);
 }
 
@@ -2318,13 +2322,14 @@ int request_nmi(unsigned int irq, irq_ha
 		/* Setup NMI state */
 		desc->istate |= IRQS_NMI;
 		retval = irq_nmi_setup(desc);
-		if (retval) {
-			__cleanup_nmi(irq, desc);
-			return -EINVAL;
-		}
-		return 0;
 	}
 
+	if (retval) {
+		__cleanup_nmi(irq, desc);
+		return -EINVAL;
+	}
+	return 0;
+
 err_irq_setup:
 	irq_chip_pm_put(&desc->irq_data);
 err_out:
author maintainer
#14 lore raw

PATCH v4 10/15 genirq: Cache the condition for /proc/interrupts exposure

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

show_interrupts() evaluates a boatload of conditions to establish whether it should expose an interrupt in /proc/interrupts or not.

That can be simplified by caching the condition in an internal status flag, which is updated when one of the relevant inputs changes.

The irq_desc::kstat_irq check is dropped because visible interrupt descriptors always have a valid pointer.

As a result the number of instructions and branches for reading /proc/interrupts is reduced significantly.

---
V4: Cover freeing of per CPU and NMI type interrupts
V3: Remove the historical kstat_irq check - Radu
V2: s/IRQF_/IRQ/ and fixup the enum treatment - Dmitry

---
 include/linux/irq.h    |    1 +
 kernel/irq/chip.c      |    2 ++
 kernel/irq/internals.h |    2 ++
 kernel/irq/manage.c    |    9 ++++++++-
 kernel/irq/proc.c      |   15 +++++++++++----
 kernel/irq/settings.h  |   13 +++++++++++++
 6 files changed, 37 insertions(+), 5 deletions(-)
include/linux/irq.h +1 -0
@@ -99,6 +99,7 @@ enum {
 	IRQ_DISABLE_UNLAZY	= (1 << 19),
 	IRQ_HIDDEN		= (1 << 20),
 	IRQ_NO_DEBUG		= (1 << 21),
+	IRQ_RESERVED		= (1 << 22),
 };
 
 #define IRQF_MODIFY_MASK	\
kernel/irq/chip.c +2 -0
@@ -1004,6 +1004,7 @@ static void
 		WARN_ON(irq_chip_pm_get(irq_desc_get_irq_data(desc)));
 		irq_activate_and_startup(desc, IRQ_RESEND);
 	}
+	irq_proc_update_valid(desc);
 }
 
 void __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
@@ -1064,6 +1065,7 @@ void irq_modify_status(unsigned int irq,
 			trigger = tmp;
 
 		irqd_set(&desc->irq_data, trigger);
+		irq_proc_update_valid(desc);
 	}
 }
 EXPORT_SYMBOL_GPL(irq_modify_status);
kernel/irq/internals.h +2 -0
@@ -123,6 +123,7 @@ extern void register_irq_proc(unsigned i
 extern void unregister_irq_proc(unsigned int irq, struct irq_desc *desc);
 extern void register_handler_proc(unsigned int irq, struct irqaction *action);
 extern void unregister_handler_proc(unsigned int irq, struct irqaction *action);
+void irq_proc_update_valid(struct irq_desc *desc);
 #else
 static inline void register_irq_proc(unsigned int irq, struct irq_desc *desc) { }
 static inline void unregister_irq_proc(unsigned int irq, struct irq_desc *desc) { }
@@ -130,6 +131,7 @@ static inline void register_handler_proc
 					 struct irqaction *action) { }
 static inline void unregister_handler_proc(unsigned int irq,
 					   struct irqaction *action) { }
+static inline void irq_proc_update_valid(struct irq_desc *desc) { }
 #endif
 
 extern bool irq_can_set_affinity_usr(unsigned int irq);
kernel/irq/manage.c +8 -1
@@ -1802,6 +1802,7 @@ static int
 		__enable_irq(desc);
 	}
 
+	irq_proc_update_valid(desc);
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 	chip_bus_sync_unlock(desc);
 	mutex_unlock(&desc->request_mutex);
@@ -1906,6 +1907,7 @@ static struct irqaction *__free_irq(stru
 		desc->affinity_hint = NULL;
 #endif
 
+	irq_proc_update_valid(desc);
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 	/*
 	 * Drop bus_lock here so the changes which were done in the chip
@@ -2047,6 +2049,8 @@ static const void *__cleanup_nmi(unsigne
 		irq_shutdown_and_deactivate(desc);
 	}
 
+	irq_proc_update_valid(desc);
+
 	if (action)
 		unregister_handler_proc(irq, action);
 	kfree(action);
@@ -2062,6 +2066,7 @@ static const void *__cleanup_nmi(unsigne
 const void *free_nmi(unsigned int irq, void *dev_id)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
+	void *ret;
 
 	if (!desc || WARN_ON(!irq_is_nmi(desc)))
 		return NULL;
@@ -2433,8 +2438,10 @@ static struct irqaction *__free_percpu_i
 		*action_ptr = action->next;
 
 		/* Demote from NMI if we killed the last action */
-		if (!desc->action)
+		if (!desc->action) {
 			desc->istate &= ~IRQS_NMI;
+			irq_proc_update_valid(desc);
+		}
 	}
 
 	unregister_handler_proc(irq, action);
kernel/irq/proc.c +11 -4
@@ -439,6 +439,16 @@ void init_irq_proc(void)
 		register_irq_proc(irq, desc);
 }
 
+void irq_proc_update_valid(struct irq_desc *desc)
+{
+	u32 set = _IRQ_PROC_VALID;
+
+	if (irq_settings_is_hidden(desc) || irq_desc_is_chained(desc) || !desc->action)
+		set = 0;
+
+	irq_settings_update_proc_valid(desc, set);
+}
+
 #ifdef CONFIG_GENERIC_IRQ_SHOW
 
 int __weak arch_show_interrupts(struct seq_file *p, int prec)
@@ -514,10 +524,7 @@ int show_interrupts(struct seq_file *p,
 
 	guard(rcu)();
 	desc = irq_to_desc(i);
-	if (!desc || irq_settings_is_hidden(desc))
-		return 0;
-
-	if (!desc->action || irq_desc_is_chained(desc) || !desc->kstat_irqs)
+	if (!desc || !irq_settings_proc_valid(desc))
 		return 0;
 
 	seq_printf(p, "%*d:", prec, i);
kernel/irq/settings.h +13 -0
@@ -18,6 +18,7 @@ enum {
 	_IRQ_DISABLE_UNLAZY	= IRQ_DISABLE_UNLAZY,
 	_IRQ_HIDDEN		= IRQ_HIDDEN,
 	_IRQ_NO_DEBUG		= IRQ_NO_DEBUG,
+	_IRQ_PROC_VALID		= IRQ_RESERVED,
 	_IRQF_MODIFY_MASK	= IRQF_MODIFY_MASK,
 };
 
@@ -34,6 +35,7 @@ enum {
 #define IRQ_DISABLE_UNLAZY	GOT_YOU_MORON
 #define IRQ_HIDDEN		GOT_YOU_MORON
 #define IRQ_NO_DEBUG		GOT_YOU_MORON
+#define IRQ_RESERVED		GOT_YOU_MORON
 #undef IRQF_MODIFY_MASK
 #define IRQF_MODIFY_MASK	GOT_YOU_MORON
 
@@ -180,3 +182,14 @@ static inline bool irq_settings_no_debug
 {
 	return desc->status_use_accessors & _IRQ_NO_DEBUG;
 }
+
+static inline bool irq_settings_proc_valid(struct irq_desc *desc)
+{
+	return desc->status_use_accessors & _IRQ_PROC_VALID;
+}
+
+static inline void irq_settings_update_proc_valid(struct irq_desc *desc, u32 set)
+{
+	desc->status_use_accessors &= ~_IRQ_PROC_VALID;
+	desc->status_use_accessors |= (set & _IRQ_PROC_VALID);
+}
author maintainer
#15 lore raw

PATCH v4 11/15 genirq: Calculate precision only when required

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Calculating the precision of the interrupt number column on every initial show_interrupt() invocation is a pointless exercise as the underlying maximum number of interrupts rarely changes.

Calculate it only when that number is modified and let show_interrupts() use the cached value.

---
 kernel/irq/internals.h |    6 ++++++
 kernel/irq/irqdesc.c   |   10 ++++++----
 kernel/irq/proc.c      |   33 +++++++++++++++++++++++----------
 3 files changed, 35 insertions(+), 14 deletions(-)
kernel/irq/internals.h +6 -0
@@ -134,6 +134,12 @@ static inline void unregister_handler_pr
 static inline void irq_proc_update_valid(struct irq_desc *desc) { }
 #endif
 
+#if defined(CONFIG_PROC_FS) && defined(CONFIG_GENERIC_IRQ_SHOW)
+void irq_proc_calc_prec(void);
+#else
+static inline void irq_proc_calc_prec(void) { }
+#endif
+
 extern bool irq_can_set_affinity_usr(unsigned int irq);
 
 extern int irq_do_set_affinity(struct irq_data *data,
kernel/irq/irqdesc.c +6 -4
@@ -157,13 +157,12 @@ EXPORT_SYMBOL_GPL(irq_get_nr_irqs);
  *
  * Return: @nr.
  */
-unsigned int irq_set_nr_irqs(unsigned int nr)
+unsigned int __init irq_set_nr_irqs(unsigned int nr)
 {
 	total_nr_irqs = nr;
-
+	irq_proc_calc_prec();
 	return nr;
 }
-EXPORT_SYMBOL_GPL(irq_set_nr_irqs);
 
 static DEFINE_MUTEX(sparse_irq_lock);
 static struct maple_tree sparse_irqs = MTREE_INIT_EXT(sparse_irqs,
@@ -544,6 +543,7 @@ static bool irq_expand_nr_irqs(unsigned
 	if (nr > MAX_SPARSE_IRQS)
 		return false;
 	total_nr_irqs = nr;
+	irq_proc_calc_prec();
 	return true;
 }
 
@@ -572,6 +572,7 @@ int __init early_irq_init(void)
 		desc = alloc_desc(i, node, 0, NULL, NULL);
 		irq_insert_desc(i, desc);
 	}
+	irq_proc_calc_prec();
 	return arch_early_irq_init();
 }
 
@@ -592,7 +593,7 @@ int __init early_irq_init(void)
 
 	init_irq_default_affinity();
 
-	printk(KERN_INFO "NR_IRQS: %d\n", NR_IRQS);
+	pr_info("NR_IRQS: %d\n", NR_IRQS);
 
 	count = ARRAY_SIZE(irq_desc);
 
@@ -602,6 +603,7 @@ int __init early_irq_init(void)
 			goto __free_desc_res;
 	}
 
+	irq_proc_calc_prec();
 	return arch_early_irq_init();
 
 __free_desc_res:
kernel/irq/proc.c +23 -10
@@ -456,10 +456,25 @@ int __weak arch_show_interrupts(struct s
 	return 0;
 }
 
+static struct irq_proc_constraints {
+	unsigned int	num_prec;
+} irq_proc_constraints __read_mostly = {
+	.num_prec	= 3,
+};
+
 #ifndef ACTUAL_NR_IRQS
 # define ACTUAL_NR_IRQS total_nr_irqs
 #endif
 
+void irq_proc_calc_prec(void)
+{
+	unsigned int prec, n;
+
+	for (prec = 3, n = 1000; prec < 10 && n <= total_nr_irqs; ++prec)
+		n *= 10;
+	WRITE_ONCE(irq_proc_constraints.num_prec, prec);
+}
+
 #define ZSTR1 "          0"
 #define ZSTR1_LEN	(sizeof(ZSTR1) - 1)
 #define ZSTR16		ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 \
@@ -498,9 +513,7 @@ void irq_proc_emit_counts(struct seq_fil
 
 int show_interrupts(struct seq_file *p, void *v)
 {
-	const unsigned int nr_irqs = total_nr_irqs;
-	static int prec;
-
+	unsigned int prec = READ_ONCE(irq_proc_constraints.num_prec);
 	int i = *(loff_t *) v, j;
 	struct irqaction *action;
 	struct irq_desc *desc;
@@ -513,9 +526,6 @@ int show_interrupts(struct seq_file *p,
 
 	/* print header and calculate the width of the first column */
 	if (i == 0) {
-		for (prec = 3, j = 1000; prec < 10 && j <= nr_irqs; ++prec)
-			j *= 10;
-
 		seq_printf(p, "%*s", prec + 8, "");
 		for_each_online_cpu(j)
 			seq_printf(p, "CPU%-8d", j);
@@ -551,13 +561,16 @@ int show_interrupts(struct seq_file *p,
 	} else {
 		seq_printf(p, "%8s", "None");
 	}
+
+	seq_putc(p, ' ');
 	if (desc->irq_data.domain)
-		seq_printf(p, " %*lu", prec, desc->irq_data.hwirq);
+		seq_put_decimal_ull_width(p, "", desc->irq_data.hwirq, prec);
 	else
 		seq_printf(p, " %*s", prec, "");
-#ifdef CONFIG_GENERIC_IRQ_SHOW_LEVEL
-	seq_printf(p, " %-8s", irqd_is_level_type(&desc->irq_data) ? "Level" : "Edge");
-#endif
+
+	if (IS_ENABLED(CONFIG_GENERIC_IRQ_SHOW_LEVEL))
+		seq_printf(p, " %-8s", irqd_is_level_type(&desc->irq_data) ? "Level" : "Edge");
+
 	if (desc->name)
 		seq_printf(p, "-%-8s", desc->name);
 
author maintainer
#16 lore raw

PATCH v4 12/15 genirq: Add rcuref count to struct irq_desc

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Prepare for a smarter iterator for /proc/interrupts so that the next interrupt descriptor can be cached after lookup.

---
 include/linux/irqdesc.h |    2 ++
 kernel/irq/internals.h  |   17 ++++++++++++++++-
 kernel/irq/irqdesc.c    |   21 +++++++++++++--------
 3 files changed, 31 insertions(+), 9 deletions(-)
include/linux/irqdesc.h +2 -0
@@ -70,6 +70,7 @@ struct irq_redirect {
  *			IRQF_NO_SUSPEND set
  * @force_resume_depth:	number of irqactions on a irq descriptor with
  *			IRQF_FORCE_RESUME set
+ * @refcnt:		Reference count mainly for /proc/interrupts
  * @rcu:		rcu head for delayed free
  * @kobj:		kobject used to represent this struct in sysfs
  * @request_mutex:	mutex to protect request/free before locking desc->lock
@@ -119,6 +120,7 @@ struct irq_desc {
 	struct dentry		*debugfs_file;
 	const char		*dev_name;
 #endif
+	rcuref_t		refcnt;
 #ifdef CONFIG_SPARSE_IRQ
 	struct rcu_head		rcu;
 	struct kobject		kobj;
kernel/irq/internals.h +16 -1
@@ -9,6 +9,7 @@
 #include <linux/irqdesc.h>
 #include <linux/kernel_stat.h>
 #include <linux/pm_runtime.h>
+#include <linux/rcuref.h>
 #include <linux/sched/clock.h>
 
 #ifdef CONFIG_SPARSE_IRQ
@@ -101,9 +102,23 @@ extern void unmask_irq(struct irq_desc *
 extern void unmask_threaded_irq(struct irq_desc *desc);
 
 #ifdef CONFIG_SPARSE_IRQ
-static inline void irq_mark_irq(unsigned int irq) { }
+static __always_inline void irq_mark_irq(unsigned int irq) { }
+void irq_desc_free_rcu(struct irq_desc *desc);
+
+static __always_inline bool irq_desc_get_ref(struct irq_desc *desc)
+{
+	return rcuref_get(&desc->refcnt);
+}
+
+static __always_inline void irq_desc_put_ref(struct irq_desc *desc)
+{
+	if (rcuref_put(&desc->refcnt))
+		irq_desc_free_rcu(desc);
+}
 #else
 extern void irq_mark_irq(unsigned int irq);
+static __always_inline bool irq_desc_get_ref(struct irq_desc *desc) { return true; }
+static __always_inline void irq_desc_put_ref(struct irq_desc *desc) { }
 #endif
 
 irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc);
kernel/irq/irqdesc.c +13 -8
@@ -137,6 +137,7 @@ static void desc_set_defaults(unsigned i
 	desc->tot_count = 0;
 	desc->name = NULL;
 	desc->owner = owner;
+	rcuref_init(&desc->refcnt, 1);
 	desc_smp_init(desc, node, affinity);
 }
 
@@ -465,6 +466,17 @@ static void delayed_free_desc(struct rcu
 	kobject_put(&desc->kobj);
 }
 
+void irq_desc_free_rcu(struct irq_desc *desc)
+{
+	/*
+	 * We free the descriptor, masks and stat fields via RCU. That
+	 * allows demultiplex interrupts to do rcu based management of
+	 * the child interrupts.
+	 * This also allows us to use rcu in kstat_irqs_usr().
+	 */
+	call_rcu(&desc->rcu, delayed_free_desc);
+}
+
 static void free_desc(unsigned int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
@@ -483,14 +495,7 @@ static void free_desc(unsigned int irq)
 	 */
 	irq_sysfs_del(desc);
 	delete_irq_desc(irq);
-
-	/*
-	 * We free the descriptor, masks and stat fields via RCU. That
-	 * allows demultiplex interrupts to do rcu based management of
-	 * the child interrupts.
-	 * This also allows us to use rcu in kstat_irqs_usr().
-	 */
-	call_rcu(&desc->rcu, delayed_free_desc);
+	irq_desc_put_ref(desc);
 }
 
 static int alloc_descs(unsigned int start, unsigned int cnt, int node,
author maintainer
#17 lore raw

PATCH v4 13/15 genirq: Expose irq_find_desc_at_or_after() in core code

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

... in preparation for a smarter iterator for /proc/interrupts.

---
V3: Add missing RCU guard and a lockdep assert - Dmitry

---
 kernel/irq/internals.h |    2 ++
 kernel/irq/irqdesc.c   |   15 ++++++++-------
 2 files changed, 10 insertions(+), 7 deletions(-)
kernel/irq/internals.h +2 -0
@@ -155,6 +155,8 @@ void irq_proc_calc_prec(void);
 static inline void irq_proc_calc_prec(void) { }
 #endif
 
+struct irq_desc *irq_find_desc_at_or_after(unsigned int offset);
+
 extern bool irq_can_set_affinity_usr(unsigned int irq);
 
 extern int irq_do_set_affinity(struct irq_data *data,
kernel/irq/irqdesc.c +8 -7
@@ -181,15 +181,12 @@ static int irq_find_free_area(unsigned i
 	return mas.index;
 }
 
-static unsigned int irq_find_at_or_after(unsigned int offset)
+struct irq_desc *irq_find_desc_at_or_after(unsigned int offset)
 {
 	unsigned long index = offset;
-	struct irq_desc *desc;
-
-	guard(rcu)();
-	desc = mt_find(&sparse_irqs, &index, total_nr_irqs);
 
-	return desc ? irq_desc_get_irq(desc) : total_nr_irqs;
+	lockdep_assert_in_rcu_read_lock();
+	return mt_find(&sparse_irqs, &index, total_nr_irqs);
 }
 
 static void irq_insert_desc(unsigned int irq, struct irq_desc *desc)
@@ -934,7 +931,11 @@ EXPORT_SYMBOL_GPL(__irq_alloc_descs);
  */
 unsigned int irq_get_next_irq(unsigned int offset)
 {
-	return irq_find_at_or_after(offset);
+	struct irq_desc *desc;
+
+	guard(rcu)();
+	desc = irq_find_desc_at_or_after(offset);
+	return desc ? irq_desc_get_irq(desc) : total_nr_irqs;
 }
 
 struct irq_desc *__irq_get_desc_lock(unsigned int irq, unsigned long *flags, bool bus,
author maintainer
#19 lore raw

PATCH v4 14/15 genirq/proc: Runtime size the chip name

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

The chip name column in the /proc/interrupt output is 8 characters and right aligned, which causes visual clutter due to the fixed length and the alignment. Many interrupt chips, e.g. PCI/MSI[X] have way longer names.

Update the length when a chip is assigned to an interrupt and utilize this information for the output. Align it left so all chip names start at the begin of the column.

Update the GDB script as well.

---
V3: New patch

---
 kernel/irq/chip.c               |    6 ++++--
 kernel/irq/internals.h          |    8 ++------
 kernel/irq/irqdomain.c          |    3 +++
 kernel/irq/proc.c               |   33 ++++++++++++++++++++++++++++-----
 kernel/irq/proc.h               |    9 +++++++++
 scripts/gdb/linux/interrupts.py |   25 ++++++++++++++++---------
 6 files changed, 62 insertions(+), 22 deletions(-)
kernel/irq/chip.c +4 -2
@@ -46,9 +46,11 @@ int irq_set_chip(unsigned int irq, const
 		scoped_irqdesc->irq_data.chip = (struct irq_chip *)(chip ?: &no_irq_chip);
 		ret = 0;
 	}
-	/* For !CONFIG_SPARSE_IRQ make the irq show up in allocated_irqs. */
-	if (!ret)
+	if (!ret) {
+		/* For !CONFIG_SPARSE_IRQ make the irq show up in allocated_irqs. */
 		irq_mark_irq(irq);
+		irq_proc_update_chip(chip);
+	}
 	return ret;
 }
 EXPORT_SYMBOL(irq_set_chip);
kernel/irq/internals.h +2 -6
@@ -12,6 +12,8 @@
 #include <linux/rcuref.h>
 #include <linux/sched/clock.h>
 
+#include "proc.h"
+
 #ifdef CONFIG_SPARSE_IRQ
 # define MAX_SPARSE_IRQS	INT_MAX
 #else
@@ -149,12 +151,6 @@ static inline void unregister_handler_pr
 static inline void irq_proc_update_valid(struct irq_desc *desc) { }
 #endif
 
-#if defined(CONFIG_PROC_FS) && defined(CONFIG_GENERIC_IRQ_SHOW)
-void irq_proc_calc_prec(void);
-#else
-static inline void irq_proc_calc_prec(void) { }
-#endif
-
 struct irq_desc *irq_find_desc_at_or_after(unsigned int offset);
 
 extern bool irq_can_set_affinity_usr(unsigned int irq);
kernel/irq/irqdomain.c +3 -0
@@ -20,6 +20,8 @@
 #include <linux/smp.h>
 #include <linux/fs.h>
 
+#include "proc.h"
+
 static LIST_HEAD(irq_domain_list);
 static DEFINE_MUTEX(irq_domain_mutex);
 
@@ -1532,6 +1534,7 @@ int irq_domain_set_hwirq_and_chip(struct
 	irq_data->chip = (struct irq_chip *)(chip ? chip : &no_irq_chip);
 	irq_data->chip_data = chip_data;
 
+	irq_proc_update_chip(chip);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(irq_domain_set_hwirq_and_chip);
kernel/irq/proc.c +28 -5
@@ -456,10 +456,14 @@ int __weak arch_show_interrupts(struct s
 	return 0;
 }
 
+static DEFINE_RAW_SPINLOCK(irq_proc_constraints_lock);
+
 static struct irq_proc_constraints {
 	unsigned int	num_prec;
+	unsigned int	chip_width;
 } irq_proc_constraints __read_mostly = {
 	.num_prec	= 3,
+	.chip_width	= 8,
 };
 
 #ifndef ACTUAL_NR_IRQS
@@ -472,7 +476,23 @@ void irq_proc_calc_prec(void)
 
 	for (prec = 3, n = 1000; prec < 10 && n <= total_nr_irqs; ++prec)
 		n *= 10;
-	WRITE_ONCE(irq_proc_constraints.num_prec, prec);
+
+	guard(raw_spinlock_irqsave)(&irq_proc_constraints_lock);
+	if (prec > irq_proc_constraints.num_prec)
+		WRITE_ONCE(irq_proc_constraints.num_prec, prec);
+}
+
+void irq_proc_update_chip(const struct irq_chip *chip)
+{
+	unsigned int len = chip && chip->name ? strlen(chip->name) : 0;
+
+	if (!len || len <= READ_ONCE(irq_proc_constraints.chip_width))
+		return;
+
+	/* Can be invoked from interrupt disabled contexts */
+	guard(raw_spinlock_irqsave)(&irq_proc_constraints_lock);
+	if (len > irq_proc_constraints.chip_width)
+		WRITE_ONCE(irq_proc_constraints.chip_width, len);
 }
 
 #define ZSTR1 "          0"
@@ -513,6 +533,7 @@ void irq_proc_emit_counts(struct seq_fil
 
 int show_interrupts(struct seq_file *p, void *v)
 {
+	unsigned int chip_width = READ_ONCE(irq_proc_constraints.chip_width);
 	unsigned int prec = READ_ONCE(irq_proc_constraints.num_prec);
 	int i = *(loff_t *) v, j;
 	struct irqaction *action;
@@ -548,18 +569,20 @@ int show_interrupts(struct seq_file *p,
 		irq_proc_emit_counts(p, &desc->kstat_irqs->cnt);
 	else
 		irq_proc_emit_zero_counts(p, num_online_cpus());
-	seq_putc(p, ' ');
+
+	/* Enforce a visual gap */
+	seq_write(p, "  ", 2);
 
 	guard(raw_spinlock_irq)(&desc->lock);
 	if (desc->irq_data.chip) {
 		if (desc->irq_data.chip->irq_print_chip)
 			desc->irq_data.chip->irq_print_chip(&desc->irq_data, p);
 		else if (desc->irq_data.chip->name)
-			seq_printf(p, "%8s", desc->irq_data.chip->name);
+			seq_printf(p, "%-*s", chip_width, desc->irq_data.chip->name);
 		else
-			seq_printf(p, "%8s", "-");
+			seq_printf(p, "%-*s", chip_width, "-");
 	} else {
-		seq_printf(p, "%8s", "None");
+		seq_printf(p, "%-*s", chip_width, "None");
 	}
 
 	seq_putc(p, ' ');
kernel/irq/proc.h new file +9 -0
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#if defined(CONFIG_PROC_FS) && defined(CONFIG_GENERIC_IRQ_SHOW)
+void irq_proc_calc_prec(void);
+void irq_proc_update_chip(const struct irq_chip *chip);
+#else
+static inline void irq_proc_calc_prec(void) { }
+static inline void irq_proc_update_chip(const struct irq_chip *chip) { }
+#endif
scripts/gdb/linux/interrupts.py +16 -9
@@ -20,7 +20,7 @@ irq_desc_type = utils.CachedType("struct
 def irqd_is_level(desc):
     return desc['irq_data']['common']['state_use_accessors'] & constants.LX_IRQD_LEVEL
 
-def show_irq_desc(prec, irq):
+def show_irq_desc(prec, chip_width, irq):
     text = ""
 
     desc = mapletree.mtree_load(gdb.parse_and_eval("&sparse_irqs"), irq)
@@ -48,7 +48,7 @@ irq_desc_type = utils.CachedType("struct
             count = cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt']
         else:
             count = 0
-        text += "%10u" % (count)
+        text += "%10u " % (count)
 
     name = "None"
     if desc['irq_data']['chip']:
@@ -58,7 +58,7 @@ irq_desc_type = utils.CachedType("struct
         else:
             name = "-"
 
-    text += "  %8s" % (name)
+    text += "  %-*s" % (chip_width, name)
 
     if desc['irq_data']['domain']:
         text += "  %*lu" % (prec, desc['irq_data']['hwirq'])
@@ -175,11 +175,18 @@ irq_desc_type = utils.CachedType("struct
 
     def invoke(self, arg, from_tty):
         nr_irqs = gdb.parse_and_eval("total_nr_irqs")
-        prec = 3
-        j = 1000
-        while prec < 10 and j <= nr_irqs:
-            prec += 1
-            j *= 10
+        constr = utils.gdb_eval_or_none('irq_proc_constraints')
+
+        if constr:
+            prec = int(constr['num_prec'])
+            chip_width = int(constr['chip_width'])
+        else:
+            prec = 3
+            j = 1000
+            while prec < 10 and j <= nr_irqs:
+                prec += 1
+                j *= 10
+            chip_width = 8
 
         gdb.write("%*s" % (prec + 8, ""))
         for cpu in cpus.each_online_cpu():
@@ -190,7 +197,7 @@ irq_desc_type = utils.CachedType("struct
             raise gdb.GdbError("Unable to find the sparse IRQ tree, is CONFIG_SPARSE_IRQ enabled?")
 
         for irq in range(nr_irqs):
-            gdb.write(show_irq_desc(prec, irq))
+            gdb.write(show_irq_desc(prec, chip_width, irq))
         gdb.write(arch_show_interrupts(prec))
 
 
Reviewed-by on v4 14/15
#20 lore raw

Re: [patch V4 14/15] genirq/proc: Runtime size the chip name

Quoted 6 lines · Thomas Gleixner

From: Thomas Gleixner <[email protected]>

The chip name column in the /proc/interrupt output is 8 characters and right aligned, which causes visual clutter due to the fixed length and the alignment. Many interrupt chips, e.g. PCI/MSI[X] have way longer names.

Quoted 7 lines

Update the length when a chip is assigned to an interrupt and utilize this information for the output. Align it left so all chip names start at the begin of the column.

Update the GDB script as well.

author maintainer
#21 lore raw

PATCH v4 15/15 genirq/proc: Speed up /proc/interrupts iteration

In reply to Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Reading /proc/interrupts iterates over the interrupt number space one by one and looks up the descriptors one by one. That's just a waste of time.

When CONFIG_GENERIC_IRQ_SHOW is enabled this can utilize the maple tree and cache the descriptor pointer efficiently for the sequence file operations.

Implement a CONFIG_GENERIC_IRQ_SHOW specific version in the core code and leave the fs/proc/ variant for the legacy architectures which ignore generic code.

This reduces the time wasted for looking up the next record significantly.

---
 fs/proc/Makefile  |    4 +
 kernel/irq/proc.c |  118 ++++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 95 insertions(+), 27 deletions(-)
fs/proc/Makefile +3 -1
@@ -16,7 +16,9 @@ proc-y	+= cmdline.o
 proc-y	+= consoles.o
 proc-y	+= cpuinfo.o
 proc-y	+= devices.o
-proc-y	+= interrupts.o
+ifneq ($(CONFIG_GENERIC_IRQ_SHOW),y)
+proc-y += interrupts.o
+endif
 proc-y	+= loadavg.o
 proc-y	+= meminfo.o
 proc-y	+= stat.o
kernel/irq/proc.c +92 -26

160 lines not on this page · raw message

Reviewed-by on v4 15/15
#22 lore raw

Re: [patch V4 15/15] genirq/proc: Speed up /proc/interrupts iteration

Quoted 16 lines · Thomas Gleixner

From: Thomas Gleixner <[email protected]>

Reading /proc/interrupts iterates over the interrupt number space one by one and looks up the descriptors one by one. That's just a waste of time.

When CONFIG_GENERIC_IRQ_SHOW is enabled this can utilize the maple tree and cache the descriptor pointer efficiently for the sequence file operations.

Implement a CONFIG_GENERIC_IRQ_SHOW specific version in the core code and leave the fs/proc/ variant for the legacy architectures which ignore generic code.

This reduces the time wasted for looking up the next record significantly.

---

[...]

kernel/irq/proc.c void irq_proc_emit_counts(struct seq_fil · line 546

Quoted 7 lines
kernel/irq/proc.c +1 -5
-	/* print header and calculate the width of the first column */
-	if (i == 0) {
-		seq_printf(p, "%*s", prec + 8, "");
-		for_each_online_cpu(j)
-			seq_printf(p, "CPU%-8d", j);
+	/* print header for the first interrupt indicated by !p>private */

nit: This comment seems a bit out of place here, since we are looking at constr->print_header directly here.

kernel/irq/proc.c void irq_proc_emit_counts(struct seq_fil · line 555

Quoted 9 lines
kernel/irq/proc.c +7 -0
+	if (constr->print_header) {
+		unsigned int cpu;
+
+		seq_printf(p, "%*s", constr->num_prec + 8, "");
+		for_each_online_cpu(cpu)
+			seq_printf(p, "CPU%-8d", cpu);
 		seq_putc(p, '\n');
+		constr->print_header = false;
 	}

While at it, moving the print_header block above the ARCH_PROC_IRQDESC check would make the code more robust. If there are no valid descriptors to display, the CPU column header would still be printed before arch_show_interrupts() output. Not a practical issue, but it makes the logic obviously correct.