riscv: don't stop itself in smp_send_stop

Only run ipi_stop on other cpus, not itself. Don't wait for ipi_stop to return, since it never does. Also, mark each cpu offline.

Signed-off-by Andreas Schwab <[email protected]>

---
  arch/riscv/kernel/smp.c | 17 ++++++++++++++++-
  1 file changed, 16 insertions(+), 1 deletion(-)

arch/riscv/kernel/smp.c +2 -0

index 57b1383e5e..5c6bb5fe5a 100644
@@ -23,6 +23,7 @@
  #include <linux/smp.h>
  #include <linux/sched.h>
  #include <linux/seq_file.h>
+#include <linux/delay.h>
 
  #include <asm/sbi.h>
  #include <asm/tlbflush.h>

@@ -148,13 +149,27 @@ void arch_send_call_function_single_ipi(int cpu)
 
  static void ipi_stop(void *unused)
  {
+	set_cpu_online (smp_processor_id(), false);

arch/riscv/kernel/smp.c void arch_send_call_function_single_ipi(int cpu) · line 164

Quoted 3 lines

arch/riscv/kernel/smp.c +3 -0

+	cpumask_copy (&mask, cpu_online_mask);
+	cpumask_clear_cpu (smp_processor_id (), &mask);
+	on_each_cpu_mask(&mask, ipi_stop, NULL, 0);

The function header of on_each_cpu_mask says func should be non-blocking. Not sure if that's a hard requirement or not.

arch/riscv/kernel/smp.c void arch_send_call_function_single_ipi(int cpu) · line 172

Quoted 8 lines

arch/riscv/kernel/smp.c +8 -0

+
+	/* Wait up to one second for other CPUs to stop */
+	timeout = USEC_PER_SEC;
+	while (num_online_cpus() > 1 && timeout--)
+		udelay(1);
+
+	if (num_online_cpus() > 1)
+		pr_warn("SMP: failed to stop secondary CPUs\n");

May be print the remaining online cpus so that we know which one failed ?

Quoted 6 lines · Atish Patra

arch/riscv/kernel/smp.c void arch_send_call_function_single_ipi(int cpu) · line 164

Quoted 3 lines

arch/riscv/kernel/smp.c +3 -0

+	cpumask_copy (&mask, cpu_online_mask);
+	cpumask_clear_cpu (smp_processor_id (), &mask);
+	on_each_cpu_mask(&mask, ipi_stop, NULL, 0);

The function header of on_each_cpu_mask says func should be non-blocking. Not sure if that's a hard requirement or not.

What does that mean?

Quoted 10 lines

arch/riscv/kernel/smp.c void arch_send_call_function_single_ipi(int cpu) · line 172

Quoted 8 lines

arch/riscv/kernel/smp.c +8 -0

+
+	/* Wait up to one second for other CPUs to stop */
+	timeout = USEC_PER_SEC;
+	while (num_online_cpus() > 1 && timeout--)
+		udelay(1);
+
+	if (num_online_cpus() > 1)
+		pr_warn("SMP: failed to stop secondary CPUs\n");

May be print the remaining online cpus so that we know which one failed ?

I have copied that from arm. The only user of smp_send_stop is panic, which can cope with that, and the probability of that happening is very low anyway.

Andreas.

Add IPI_CPU_STOP message and use it in smp_send_stop to stop other cpus, but not itself. Mark cpu offline on reception of IPI_CPU_STOP.

Signed-off-by Andreas Schwab <[email protected]>

---
  arch/riscv/kernel/smp.c | 43 ++++++++++++++++++++++++++++++++++-------
  1 file changed, 36 insertions(+), 7 deletions(-)

arch/riscv/kernel/smp.c +29 -7

index 57b1383e5e..b813264416 100644
@@ -23,6 +23,7 @@
  #include <linux/smp.h>
  #include <linux/sched.h>
  #include <linux/seq_file.h>
+#include <linux/delay.h>
 
  #include <asm/sbi.h>
  #include <asm/tlbflush.h>

@@ -31,6 +32,7 @@
  enum ipi_message_type {
  	IPI_RESCHEDULE,
  	IPI_CALL_FUNC,
+	IPI_CPU_STOP,
  	IPI_MAX
  };
 

@@ -66,6 +68,13 @@ int setup_profiling_timer(unsigned int multiplier)
  	return -EINVAL;
  }
 
+static void ipi_stop(void)
+{
+	set_cpu_online (smp_processor_id(), false);
+	while (1)
+		wait_for_interrupt();
+}
+
  void riscv_software_interrupt(void)
  {
  	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;

@@ -94,6 +103,11 @@ void riscv_software_interrupt(void)
  			generic_smp_call_function_interrupt();
  		}
 
+		if (ops & (1 << IPI_CPU_STOP)) {
+			stats[IPI_CPU_STOP]++;
+			ipi_stop();
+		}
+
  		BUG_ON((ops >> IPI_MAX) != 0);
 
  		/* Order data access and bit testing. */

@@ -121,6 +135,7 @@ send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
  static const char * const ipi_names[] = {
  	[IPI_RESCHEDULE]	= "Rescheduling interrupts",
  	[IPI_CALL_FUNC]		= "Function call interrupts",
+	[IPI_CPU_STOP]		= "CPU stop interrupts",
  };
 
  void show_ipi_stats(struct seq_file *p, int prec)

@@ -146,15 +161,29 @@ void arch_send_call_function_single_ipi(int cpu)
  	send_ipi_message(cpumask_of(cpu), IPI_CALL_FUNC);
  }
 
-static void ipi_stop(void *unused)
-{
-	while (1)
-		wait_for_interrupt();
-}
-
  void smp_send_stop(void)
  {
-	on_each_cpu(ipi_stop, NULL, 1);
+	unsigned long timeout;
+
+	if (num_online_cpus() > 1) {
+		cpumask_t mask;
+
+		cpumask_copy(&mask, cpu_online_mask);
+		cpumask_clear_cpu(smp_processor_id(), &mask);
+
+		if (system_state <= SYSTEM_RUNNING)
+			pr_crit("SMP: stopping secondary CPUs\n");
+		send_ipi_message(&mask, IPI_CPU_STOP);
+	}
+
+	/* Wait up to one second for other CPUs to stop */

Quoted 90 lines · Andreas Schwab

Add IPI_CPU_STOP message and use it in smp_send_stop to stop other cpus, but not itself. Mark cpu offline on reception of IPI_CPU_STOP.

Signed-off-by Andreas Schwab <[email protected]>

---
  arch/riscv/kernel/smp.c | 43 ++++++++++++++++++++++++++++++++++-------
  1 file changed, 36 insertions(+), 7 deletions(-)

arch/riscv/kernel/smp.c +29 -7

index 57b1383e5e..b813264416 100644
@@ -23,6 +23,7 @@
  #include <linux/smp.h>
  #include <linux/sched.h>
  #include <linux/seq_file.h>
+#include <linux/delay.h>
 
  #include <asm/sbi.h>
  #include <asm/tlbflush.h>

@@ -31,6 +32,7 @@
  enum ipi_message_type {
  	IPI_RESCHEDULE,
  	IPI_CALL_FUNC,
+	IPI_CPU_STOP,
  	IPI_MAX
  };
 

@@ -66,6 +68,13 @@ int setup_profiling_timer(unsigned int multiplier)
  	return -EINVAL;
  }
 
+static void ipi_stop(void)
+{
+	set_cpu_online (smp_processor_id(), false);
+	while (1)
+		wait_for_interrupt();
+}
+
  void riscv_software_interrupt(void)
  {
  	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;

@@ -94,6 +103,11 @@ void riscv_software_interrupt(void)
  			generic_smp_call_function_interrupt();
  		}
 
+		if (ops & (1 << IPI_CPU_STOP)) {
+			stats[IPI_CPU_STOP]++;
+			ipi_stop();
+		}
+
  		BUG_ON((ops >> IPI_MAX) != 0);
 
  		/* Order data access and bit testing. */

@@ -121,6 +135,7 @@ send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
  static const char * const ipi_names[] = {
  	[IPI_RESCHEDULE]	= "Rescheduling interrupts",
  	[IPI_CALL_FUNC]		= "Function call interrupts",
+	[IPI_CPU_STOP]		= "CPU stop interrupts",
  };
 
  void show_ipi_stats(struct seq_file *p, int prec)

@@ -146,15 +161,29 @@ void arch_send_call_function_single_ipi(int cpu)
  	send_ipi_message(cpumask_of(cpu), IPI_CALL_FUNC);
  }
 
-static void ipi_stop(void *unused)
-{
-	while (1)
-		wait_for_interrupt();
-}
-
  void smp_send_stop(void)
  {
-	on_each_cpu(ipi_stop, NULL, 1);
+	unsigned long timeout;
+
+	if (num_online_cpus() > 1) {
+		cpumask_t mask;
+
+		cpumask_copy(&mask, cpu_online_mask);
+		cpumask_clear_cpu(smp_processor_id(), &mask);
+
+		if (system_state <= SYSTEM_RUNNING)
+			pr_crit("SMP: stopping secondary CPUs\n");
+		send_ipi_message(&mask, IPI_CPU_STOP);
+	}
+
+	/* Wait up to one second for other CPUs to stop */

arch/riscv/kernel/smp.c void arch_send_call_function_single_ipi(int cpu) · line 189

Quoted 10 lines

arch/riscv/kernel/smp.c +7 -0

+	timeout = USEC_PER_SEC;
+	while (num_online_cpus() > 1 && timeout--)
+		udelay(1);
+
+	if (num_online_cpus() > 1)
+		pr_warning("SMP: failed to stop secondary CPUs %*pbl\n",
+			   cpumask_pr_args(cpu_online_mask));
  }
 
  void smp_send_reschedule(int cpu)

Checkpatch warnings.
WARNING: space prohibited between function name and open parenthesis '(' #40: FILE: arch/riscv/kernel/smp.c:73:
+ set_cpu_online (smp_processor_id(), false);

WARNING: Prefer pr_warn(... to pr_warning(...
#100: FILE: arch/riscv/kernel/smp.c:185:
+ pr_warning("SMP: failed to stop secondary CPUs %*pbl\n",

Otherwise, Looks good to me.

Reviewed-by Atish Patra <[email protected]>