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perf: Fix dangling cgroup pointer in cpuctx

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Commit a3c3c6667("perf/core: Fix child_total_time_enabled accounting
bug at task exit") moves the event->state update to before
list_del_event(). This makes the event->state test in list_del_event()
always false; never calling perf_cgroup_event_disable().

As a result, cpuctx->cgrp won't be cleared properly; causing havoc.

Fixes: a3c3c6667("perf/core: Fix child_total_time_enabled accounting bug at task exit")
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: David Wang <00107082@163.com>
Link: https://lore.kernel.org/all/aD2TspKH%2F7yvfYoO@e129823.arm.com/
This commit is contained in:
Yeoreum Yun 2025-06-02 19:40:49 +01:00 committed by Peter Zijlstra
parent 61988e36dc
commit 3b7a34aebb
1 changed files with 6 additions and 15 deletions
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21
kernel/events/core.c
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@ -2120,18 +2120,6 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
if (event->group_leader == event)
del_event_from_groups(event, ctx);
/*
* If event was in error state, then keep it
* that way, otherwise bogus counts will be
* returned on read(). The only way to get out
* of error state is by explicit re-enabling
* of the event
*/
if (event->state > PERF_EVENT_STATE_OFF) {
perf_cgroup_event_disable(event, ctx);
perf_event_set_state(event, PERF_EVENT_STATE_OFF);
}
ctx->generation++;
event->pmu_ctx->nr_events--;
}
@ -2488,11 +2476,14 @@ __perf_remove_from_context(struct perf_event *event,
state = PERF_EVENT_STATE_EXIT;
if (flags & DETACH_REVOKE)
state = PERF_EVENT_STATE_REVOKED;
if (flags & DETACH_DEAD) {
event->pending_disable = 1;
if (flags & DETACH_DEAD)
state = PERF_EVENT_STATE_DEAD;
}
event_sched_out(event, ctx);
if (event->state > PERF_EVENT_STATE_OFF)
perf_cgroup_event_disable(event, ctx);
perf_event_set_state(event, min(event->state, state));
if (flags & DETACH_GROUP)