perf: Cancel the mux hrtimer during CPU hotplug to avoid migration
The current design of hrtimers migrates the pinned timers to a
different CPU upon its hotplug. However, perf-core needs to
maintain the mux-hrtimers on a per CPU basis. That is, each
hrtimer carries the context for that particular CPU and would
lose this context if it gets migrated to a different CPU. As a
result, cancel the hrtimer for the CPU that's about to go down
and restart it (if required) when the perf-events are being created.
Change-Id: I7a1d0456208855e3a99a7d49e59c6dae811d146e
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
[mojha@codeaurora.org: Resolved merge conflict and added missing
`cpuctx` variable to avoid build failure]
Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 47c5b39..d32e7b8 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -266,7 +266,7 @@
int capabilities;
int * __percpu pmu_disable_count;
- struct perf_cpu_context * __percpu pmu_cpu_context;
+ struct perf_cpu_context __percpu *pmu_cpu_context;
atomic_t exclusive_cnt; /* < 0: cpu; > 0: tsk */
int task_ctx_nr;
int hrtimer_interval_ms;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index eb57fb3..6be8ea2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11212,13 +11212,25 @@
static void perf_event_exit_cpu_context(int cpu)
{
+ struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx;
+ unsigned long flags;
struct pmu *pmu;
int idx;
idx = srcu_read_lock(&pmus_srcu);
list_for_each_entry_rcu(pmu, &pmus, entry) {
- ctx = &per_cpu_ptr(pmu->pmu_cpu_context, cpu)->ctx;
+ cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
+ ctx = &cpuctx->ctx;
+
+ /* Cancel the mux hrtimer to avoid CPU migration */
+ if (pmu->task_ctx_nr != perf_sw_context) {
+ raw_spin_lock_irqsave(&cpuctx->hrtimer_lock, flags);
+ hrtimer_cancel(&cpuctx->hrtimer);
+ cpuctx->hrtimer_active = 0;
+ raw_spin_unlock_irqrestore(&cpuctx->hrtimer_lock,
+ flags);
+ }
mutex_lock(&ctx->mutex);
smp_call_function_single(cpu, __perf_event_exit_context, ctx, 1);