Dump ipipe trace on kernel oopses

This is not a must-have, and it is not for all archs so far anyway:

Dump an I-pipe panic trace on ordinary kernel oopses. For me this turned out to be useful already, but not everyone may love to see his/her console flooded with call-history traces on oops, though this only happens if the tracer is enabled.

Comments welcome.

Quoted 9 lines · Jan Kiszka

This is not a must-have, and it is not for all archs so far anyway:

Dump an I-pipe panic trace on ordinary kernel oopses. For me this turned out to be useful already, but not everyone may love to see his/her console flooded with call-history traces on oops, though this only happens if the tracer is enabled.

Comments welcome.

Following your suggestion, this version makes the panic freezing a configurable option. Also, it adds support for x86_64 (note that all arch bits are in the same patch here!) and should now cover any arch I-pipe runs on.

I would say: No longer an RFC, now a request to apply.

Quoted 7 lines · Jan Kiszka

This is not a must-have, and it is not for all archs so far anyway:

Dump an I-pipe panic trace on ordinary kernel oopses. For me this turned out to be useful already, but not everyone may love to see his/her console flooded with call-history traces on oops, though this only happens if the tracer is enabled.

Quoted 2 lines

Comments welcome.

Following your suggestion, this version makes the panic freezing a configurable option. Also, it adds support for x86_64 (note that all arch bits are in the same patch here!) and should now cover any arch I-pipe runs on.

I would say: No longer an RFC, now a request to apply.

Jan

---
 arch/i386/mm/fault.c        |    5 +++
 arch/x86_64/mm/fault.c      |    3 ++
 include/linux/ipipe_trace.h |   10 +++----
 kernel/ipipe/Kconfig.debug  |   18 +++++++++---
 kernel/ipipe/tracer.c       |   62 ++++++++++++++++++++++++--------------------
 lib/bust_spinlocks.c        |    5 +++
 6 files changed, 65 insertions(+), 38 deletions(-)

Index: linux-2.6.20/arch/i386/mm/fault.c
===================================================================

arch/i386/mm/fault.c +5 -0

@@ -23,6 +23,7 @@
 #include <linux/module.h>
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
+#include <linux/ipipe_trace.h>
 
 #include <asm/system.h>
 #include <asm/desc.h>

@@ -68,9 +69,13 @@ void bust_spinlocks(int yes)
 	int loglevel_save = console_loglevel;
 
 	if (yes) {
+		ipipe_trace_panic_freeze();
 		oops_in_progress = 1;
 		return;
 	}
+
+	ipipe_trace_panic_dump();
+
 #ifdef CONFIG_VT
 	unblank_screen();
 #endif

Index: linux-2.6.20/lib/bust_spinlocks.c
===================================================================

lib/bust_spinlocks.c +5 -0

@@ -12,14 +12,19 @@
 #include <linux/tty.h>
 #include <linux/wait.h>
 #include <linux/vt_kern.h>
+#include <linux/ipipe_trace.h>
 
 
 void bust_spinlocks(int yes)
 {
 	if (yes) {
+		ipipe_trace_panic_freeze();
 		oops_in_progress = 1;
 	} else {
 		int loglevel_save = console_loglevel;
+
+		ipipe_trace_panic_dump();
+
 #ifdef CONFIG_VT
 		unblank_screen();
 #endif

Index: linux-2.6.20/include/linux/ipipe_trace.h
===================================================================

include/linux/ipipe_trace.h +5 -5

@@ -2,7 +2,7 @@
  * include/linux/ipipe_trace.h
  *
  * Copyright (C) 2005 Luotao Fu.
- *               2005, 2006 Jan Kiszka.
+ *               2005-2007 Jan Kiszka.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by

@@ -23,8 +23,6 @@
 #ifndef _LINUX_IPIPE_TRACE_H
 #define _LINUX_IPIPE_TRACE_H
 
-#ifdef CONFIG_IPIPE_TRACE
-
 #include <linux/types.h>
 
 void ipipe_trace_begin(unsigned long v);

@@ -36,14 +34,16 @@ void ipipe_trace_pid(pid_t pid, short pr
 int ipipe_trace_max_reset(void);
 int ipipe_trace_frozen_reset(void);
 
+#ifdef CONFIG_IPIPE_TRACE_PANIC
+
 void ipipe_trace_panic_freeze(void);
 void ipipe_trace_panic_dump(void);
 
-#else /* !CONFIG_IPIPE_TRACE */
+#else /* !CONFIG_IPIPE_TRACE_PANIC */
 
 static inline void ipipe_trace_panic_freeze(void) { }
 static inline void ipipe_trace_panic_dump(void) { }
 
-#endif /* !CONFIG_IPIPE_TRACE */
+#endif /* !CONFIG_IPIPE_TRACE_PANIC */
 
 #endif	/* !__LINUX_IPIPE_H */

Index: linux-2.6.20/kernel/ipipe/Kconfig.debug
===================================================================

kernel/ipipe/Kconfig.debug +13 -5

@@ -31,9 +31,10 @@ config IPIPE_TRACE
 	  in-kernel tracing API. The collected data and runtime control
 	  is available via /proc/ipipe/trace/*.
 
+if IPIPE_TRACE
+
 config IPIPE_TRACE_ENABLE
 	bool "Enable tracing on boot"
-	depends on IPIPE_TRACE
 	default y
 	---help---
 	  Disable this option if you want to arm the tracer after booting

@@ -42,7 +43,6 @@ config IPIPE_TRACE_ENABLE
 
 config IPIPE_TRACE_MCOUNT
 	bool "Instrument function entries"
-	depends on IPIPE_TRACE
 	default y
 	---help---
 	  When enabled, records every kernel function entry in the tracer

@@ -53,7 +53,6 @@ config IPIPE_TRACE_MCOUNT
 
 config IPIPE_TRACE_IRQSOFF
 	bool "Trace IRQs-off times"
-	depends on IPIPE_TRACE
 	default y
 	---help---
 	  Activate this option if I-pipe shall trace the longest path

@@ -63,14 +62,12 @@ config IPIPE_TRACE_SHIFT
 	int "Depth of trace log (14 => 16Kpoints, 15 => 32Kpoints)"
 	range 10 18
 	default 14
-	depends on IPIPE_TRACE
 	---help---
 	  The number of trace points to hold tracing data for each
 	  trace path, as a power of 2.
 
 config IPIPE_TRACE_VMALLOC
 	bool "Use vmalloc'ed trace buffer"
-	depends on IPIPE_TRACE
 	default y if EMBEDDED
 	---help---
 	  Instead of reserving static kernel data, the required buffer

@@ -79,9 +76,20 @@ config IPIPE_TRACE_VMALLOC
 	  but it slightly degrades overall performance. Try this option
 	  when a traced kernel hangs unexpectedly at boot time.
 
+config IPIPE_TRACE_PANIC
+	bool "Enable panic back traces"
+	default y
+	---help---
+	  Provides services to freeze and dump a back trace on panic
+	  situations. This is used on IPIPE_DEBUG_CONTEXT exceptions
+	  as well as ordinary kernel oopses. You can control the number
+	  of printed back trace points via /proc/ipipe/trace.
+
 config IPIPE_TRACE_ENABLE_VALUE
 	int
 	default 0 if !IPIPE_TRACE_ENABLE
 	default 1 if IPIPE_TRACE_ENABLE
 
 endif
+
+endif

Index: linux-2.6.20/kernel/ipipe/tracer.c
===================================================================

kernel/ipipe/tracer.c +34 -28

@@ -132,7 +132,9 @@ static unsigned long trace_overhead;
 
 static DEFINE_MUTEX(out_mutex);
 static struct ipipe_trace_path *print_path;
+#ifdef CONFIG_IPIPE_TRACE_PANIC
 static struct ipipe_trace_path *panic_path;
+#endif /* CONFIG_IPIPE_TRACE_PANIC */
 static int print_pre_trace;
 static int print_post_trace;
 

@@ -564,25 +566,6 @@ int ipipe_trace_frozen_reset(void)
 }
 EXPORT_SYMBOL(ipipe_trace_frozen_reset);
 
-void ipipe_trace_panic_freeze(void)
-{
-	unsigned long flags;
-	int cpuid;
-
-	if (!ipipe_trace_enable)
-		return;
-
-	ipipe_trace_enable = 0;
-	local_irq_save_hw_notrace(flags);
-
-	cpuid = raw_smp_processor_id();
-
-	panic_path = &trace_paths[cpuid][active_path[cpuid]];
-
-	local_irq_restore_hw(flags);
-}
-EXPORT_SYMBOL(ipipe_trace_panic_freeze);
-
 static void
 __ipipe_get_task_info(char *task_info, struct ipipe_trace_point *point,
                       int trylock)

@@ -615,6 +598,26 @@ __ipipe_get_task_info(char *task_info, s
 	strcpy(task_info + (11 - strlen(buf)), buf);
 }
 
+#ifdef CONFIG_IPIPE_TRACE_PANIC
+void ipipe_trace_panic_freeze(void)
+{
+	unsigned long flags;
+	int cpuid;
+
+	if (!ipipe_trace_enable)
+		return;
+
+	ipipe_trace_enable = 0;
+	local_irq_save_hw_notrace(flags);
+
+	cpuid = raw_smp_processor_id();
+
+	panic_path = &trace_paths[cpuid][active_path[cpuid]];
+
+	local_irq_restore_hw(flags);
+}
+EXPORT_SYMBOL(ipipe_trace_panic_freeze);
+
 void ipipe_trace_panic_dump(void)
 {
 	int cnt = back_trace;

@@ -681,6 +684,7 @@ void ipipe_trace_panic_dump(void)
 	panic_path = NULL;
 }
 EXPORT_SYMBOL(ipipe_trace_panic_dump);
+#endif /* CONFIG_IPIPE_TRACE_PANIC */
 
 
 /* --- /proc output --- */

@@ -803,8 +807,17 @@ static void __ipipe_print_symname(struct
 
 	sym_name = kallsyms_lookup(eip, &size, &offset, &modname, namebuf);
 
-	/* printing to /proc? */
-	if (m) {
+#ifdef CONFIG_IPIPE_TRACE_PANIC
+	if (!m) {
+		/* panic dump */
+		if (sym_name) {
+			printk("%s+0x%lx", sym_name, offset);
+			if (modname)
+				printk(" [%s]", modname);
+		}
+	} else
+#endif /* CONFIG_IPIPE_TRACE_PANIC */
+	{
 		if (sym_name) {
 			if (verbose_trace) {
 				seq_printf(m, "%s+0x%lx", sym_name, offset);

@@ -814,13 +827,6 @@ static void __ipipe_print_symname(struct
 				seq_puts(m, sym_name);
 		} else
 			seq_printf(m, "<%08lx>", eip);
-	} else {
-		/* panic dump */
-		if (sym_name) {
-			printk("%s+0x%lx", sym_name, offset);
-			if (modname)
-				printk(" [%s]", modname);
-		}
 	}
 }
 

Index: linux-2.6.20/arch/x86_64/mm/fault.c
===================================================================

arch/x86_64/mm/fault.c +3 -0

@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
+#include <linux/ipipe_trace.h>
 
 #include <asm/system.h>
 #include <asm/pgalloc.h>

@@ -73,8 +74,10 @@ void bust_spinlocks(int yes)
 {
 	int loglevel_save = console_loglevel;
 	if (yes) {
+		ipipe_trace_panic_freeze();
 		oops_in_progress = 1;
 	} else {
+		ipipe_trace_panic_dump();
 #ifdef CONFIG_VT
 		unblank_screen();
 #endif