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perf/core: Fix endless multiplex timer

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Kan and Andi reported that we fail to kill rotation when the flexible
events go empty, but the context does not. XXX moar

Fixes: fd7d55172d ("perf/cgroups: Don't rotate events for cgroups unnecessarily")
Reported-by: Andi Kleen <ak@linux.intel.com>
Reported-by: Kan Liang <kan.liang@linux.intel.com>
Tested-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200305123851.GX2596@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2020-03-05 13:38:51 +01:00
parent d8a7386897
commit 90c91dfb86
1 changed files with 14 additions and 6 deletions
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20
kernel/events/core.c
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@ -2291,6 +2291,7 @@ __perf_remove_from_context(struct perf_event *event,
if (!ctx->nr_events && ctx->is_active) {
ctx->is_active = 0;
ctx->rotate_necessary = 0;
if (ctx->task) {
WARN_ON_ONCE(cpuctx->task_ctx != ctx);
cpuctx->task_ctx = NULL;
@ -3188,12 +3189,6 @@ static void ctx_sched_out(struct perf_event_context *ctx,
if (!ctx->nr_active || !(is_active & EVENT_ALL))
return;
/*
* If we had been multiplexing, no rotations are necessary, now no events
* are active.
*/
ctx->rotate_necessary = 0;
perf_pmu_disable(ctx->pmu);
if (is_active & EVENT_PINNED) {
list_for_each_entry_safe(event, tmp, &ctx->pinned_active, active_list)
@ -3203,6 +3198,13 @@ static void ctx_sched_out(struct perf_event_context *ctx,
if (is_active & EVENT_FLEXIBLE) {
list_for_each_entry_safe(event, tmp, &ctx->flexible_active, active_list)
group_sched_out(event, cpuctx, ctx);
/*
* Since we cleared EVENT_FLEXIBLE, also clear
* rotate_necessary, is will be reset by
* ctx_flexible_sched_in() when needed.
*/
ctx->rotate_necessary = 0;
}
perf_pmu_enable(ctx->pmu);
}
@ -3985,6 +3987,12 @@ ctx_event_to_rotate(struct perf_event_context *ctx)
typeof(*event), group_node);
}
/*
* Unconditionally clear rotate_necessary; if ctx_flexible_sched_in()
* finds there are unschedulable events, it will set it again.
*/
ctx->rotate_necessary = 0;
return event;
}