Commit 00d5d15b authored Mar 10, 2020 by Chris Wilson Committed by Tejun Heo Mar 12, 2020

workqueue: Mark up unlocked access to wq->first_flusher



[ 7329.671518] BUG: KCSAN: data-race in flush_workqueue / flush_workqueue
[ 7329.671549]
[ 7329.671572] write to 0xffff8881f65fb250 of 8 bytes by task 37173 on cpu 2:
[ 7329.671607]  flush_workqueue+0x3bc/0x9b0 (kernel/workqueue.c:2844)
[ 7329.672527]
[ 7329.672540] read to 0xffff8881f65fb250 of 8 bytes by task 37175 on cpu 0:
[ 7329.672571]  flush_workqueue+0x28d/0x9b0 (kernel/workqueue.c:2835)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

parent 2333e829

kernel/workqueue.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -2832,7 +2832,7 @@ void flush_workqueue(struct workqueue_struct *wq)
		* First flushers are responsible for cascading flushes and
		* handling overflow. Non-first flushers can simply return.
		*/
		if (wq->first_flusher != &this_flusher)
		if (READ_ONCE(wq->first_flusher) != &this_flusher)
		return;

		mutex_lock(&wq->mutex);
		@@ -2841,7 +2841,7 @@ void flush_workqueue(struct workqueue_struct *wq)
		if (wq->first_flusher != &this_flusher)
		goto out_unlock;

		wq->first_flusher = NULL;
		WRITE_ONCE(wq->first_flusher, NULL);

		WARN_ON_ONCE(!list_empty(&this_flusher.list));
		WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);

Admin message