Commit 3b7a34ae authored by Yeoreum Yun's avatar Yeoreum Yun Committed by Peter Zijlstra
Browse files

perf: Fix dangling cgroup pointer in cpuctx 



Commit a3c3c666("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: a3c3c666("perf/core: Fix child_total_time_enabled accounting bug at task exit")
Signed-off-by: default avatarYeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarDavid Wang <00107082@163.com>
Link: https://lore.kernel.org/all/aD2TspKH%2F7yvfYoO@e129823.arm.com/
parent 61988e36

kernel/events/core.c

+6 −15
Original line number Diff line number Diff line
@@ -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)