sched: Add helper nr_context_switches_cpu()

Zhen Lei · chantra · commit 198b21cafad3 · 2022-10-17T03:38:24.000-07:00
Returns the number of context switches on the specified CPU, which can be
used to diagnose rcu stall.

Signed-off-by: Zhen Lei &lt;thunder.leizhen@huawei.com&gt;
diff --git 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
@@ -5221,6 +5221,11 @@ 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;

Original file line number	Diff line number	Diff line change
`@@ -5221,6 +5221,11 @@ bool single_task_running(void)`
`5221`	`5221`	`}`
`5222`	`5222`	`EXPORT_SYMBOL(single_task_running);`
`5223`	`5223`
	`5224`	`+unsigned long long nr_context_switches_cpu(int cpu)`
	`5225`	`+{`
	`5226`	`+ return cpu_rq(cpu)->nr_switches;`
	`5227`	`+}`
	`5228`	`+`
`5224`	`5229`	`unsigned long long nr_context_switches(void)`
`5225`	`5230`	`{`
`5226`	`5231`	`int i;`