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authorPeter Zijlstra <peterz@infradead.org>2020-03-05 13:38:51 +0100
committerPeter Zijlstra <peterz@infradead.org>2020-03-20 13:06:22 +0100
commit90c91dfb86d0ff545bd329d3ddd72c147e2ae198 (patch)
tree3dc7861dc6d78390198dddbc38847e35a914b098
parentd8a738689794c42c3844284b99ddf165d10a724e (diff)
perf/core: Fix endless multiplex timer
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.net
-rw-r--r--kernel/events/core.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index ccf8d4fc6374..b5a68d26f0b9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -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;
}