From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 90c91dfb86d0ff545bd329d3ddd72c147e2ae198 ]
Kan and Andi reported that we fail to kill rotation when the flexible events go empty, but the context does not. XXX moar
Fixes: fd7d55172d1e ("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.... Cc: stable@vger.kernel.org # 4.19 Signed-off-by: Wen Yang wenyang@linux.alibaba.com --- kernel/events/core.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 335fbde..0d60c82 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2081,6 +2081,7 @@ static inline int pmu_filter_match(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; @@ -2957,12 +2958,6 @@ 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) @@ -2972,6 +2967,13 @@ 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); } @@ -3710,6 +3712,12 @@ static void rotate_ctx(struct perf_event_context *ctx, struct perf_event *event) 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; }