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Subject[PATCH] perf/core: remove invalid warning from list_update_cgroup_event
Date
The warning introduced in commit:

979bfef8607c ("perf/core: Do not set cpuctx->cgrp for unscheduled cgroups")

assumed that a cgroup switch always precedes list_del_event. This is not
the case. Remove warning.

Make sure that cpuctx->cgrp is NULL until a cgroup event is sched in or
ctx->nr_cgroups == 0.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
kernel/events/core.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6ee1feb..02c8421 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -903,17 +903,14 @@ list_update_cgroup_event(struct perf_event *event,
*/
cpuctx = __get_cpu_context(ctx);

- /* Only set/clear cpuctx->cgrp if current task uses event->cgrp. */
- if (perf_cgroup_from_task(current, ctx) != event->cgrp) {
- /*
- * We are removing the last cpu event in this context.
- * If that event is not active in this cpu, cpuctx->cgrp
- * should've been cleared by perf_cgroup_switch.
- */
- WARN_ON_ONCE(!add && cpuctx->cgrp);
- return;
- }
- cpuctx->cgrp = add ? event->cgrp : NULL;
+ /*
+ * cpuctx->cgrp is NULL until a cgroup event is sched in or
+ * ctx->nr_cgroup == 0 .
+ */
+ if (add && perf_cgroup_from_task(current, ctx) == event->cgrp)
+ cpuctx->cgrp = event->cgrp;
+ else if (!add)
+ cpuctx->cgrp = NULL;
}

#else /* !CONFIG_CGROUP_PERF */
--
2.8.0.rc3.226.g39d4020
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