From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit 90c91dfb86d0ff545bd329d3ddd72c147e2ae198 upstream.
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@xxxxxxxxxxxxxxx>
Reported-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Tested-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Wen Yang <wenyang@xxxxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200305123851.GX2596@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/events/core.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2086,6 +2086,7 @@ __perf_remove_from_context(struct perf_e
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;
@@ -2952,12 +2953,6 @@ static void ctx_sched_out(struct perf_ev
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)
@@ -2967,6 +2962,13 @@ static void ctx_sched_out(struct perf_ev
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);
}
@@ -3705,6 +3707,12 @@ ctx_event_to_rotate(struct perf_event_co
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;
}
