perf/core: Fix the WARN_ON_ONCE is out of lock protected region

commit 3172fb986666 ("perf/core: Fix WARN in perf_cgroup_switch()") try to
fix a concurrency problem between perf_cgroup_switch and
perf_cgroup_event_disable. But it does not to move the WARN_ON_ONCE into
lock-protected region, so the warning is still be triggered.

Fixes: 3172fb986666 ("perf/core: Fix WARN in perf_cgroup_switch()")
Signed-off-by: Luo Gengkun <luogengkun@huaweicloud.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250626135403.2454105-1-luogengkun@huaweicloud.com

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7281230044d0dce87f460e9ff7c5696737d786a9..bf2118c2212663040b39857c0f6d9ccfe258d295 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -951,8 +951,6 @@ static void perf_cgroup_switch(struct task_struct *task)
        if (READ_ONCE(cpuctx->cgrp) == NULL)
                return;
 
-       WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0);
-
        cgrp = perf_cgroup_from_task(task, NULL);
        if (READ_ONCE(cpuctx->cgrp) == cgrp)
                return;
@@ -964,6 +962,8 @@ static void perf_cgroup_switch(struct task_struct *task)
        if (READ_ONCE(cpuctx->cgrp) == NULL)
                return;
 
+       WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0);
+
        perf_ctx_disable(&cpuctx->ctx, true);
 
        ctx_sched_out(&cpuctx->ctx, NULL, EVENT_ALL|EVENT_CGROUP);