[2/3] sched: Add helper nr_context_switches_cpu()

Commit Message

Leizhen (ThunderTown) Oct. 17, 2022, 10:01 a.m. UTC

Returns the number of context switches on the specified CPU, which can be
used to diagnose rcu stall.

Signed-off-by: Zhen Lei <[e-mail]>
---
 include/linux/kernel_stat.h | 1 +
 kernel/sched/core.c         | 5 +++++
 2 files changed, 6 insertions(+)

Patch

diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 61d427c1962bf1c..ac4f9302b559c9d 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -52,6 +52,7 @@  DECLARE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
 #define kstat_cpu(cpu) per_cpu(kstat, cpu)
 #define kcpustat_cpu(cpu) per_cpu(kernel_cpustat, cpu)
 
+extern unsigned long long nr_context_switches_cpu(int cpu);
 extern unsigned long long nr_context_switches(void);
 
 extern unsigned int kstat_irqs_cpu(unsigned int irq, int cpu);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5800b0623ff3068..a0d19f67f2046d9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5229,6 +5229,11 @@  bool single_task_running(void)
 }
 EXPORT_SYMBOL(single_task_running);
 
+unsigned long long nr_context_switches_cpu(int cpu)
+{
+	return cpu_rq(cpu)->nr_switches;
+}
+
 unsigned long long nr_context_switches(void)
 {
 	int i;