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authorLai Jiangshan <laijs@cn.fujitsu.com>2014-04-18 11:04:16 -0400
committerTejun Heo <tj@kernel.org>2014-04-18 12:33:29 -0400
commit77668c8b559e4fe2acf2a0749c7c83cde49a5025 (patch)
tree689828b6f65983dff2ddface82a41bea2bb1adec /kernel/workqueue.c
parent4d595b866d2c653dc90a492b9973a834eabfa354 (diff)
workqueue: fix a possible race condition between rescuer and pwq-release
There is a race condition between rescuer_thread() and pwq_unbound_release_workfn(). Even after a pwq is scheduled for rescue, the associated work items may be consumed by any worker. If all of them are consumed before the rescuer gets to them and the pwq's base ref was put due to attribute change, the pwq may be released while still being linked on @wq->maydays list making the rescuer dereference already freed pwq later. Make send_mayday() pin the target pwq until the rescuer is done with it. tj: Updated comment and patch description. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org # v3.10+
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r--kernel/workqueue.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 6ba0c6054224..8edc87185427 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1916,6 +1916,12 @@ static void send_mayday(struct work_struct *work)
/* mayday mayday mayday */
if (list_empty(&pwq->mayday_node)) {
+ /*
+ * If @pwq is for an unbound wq, its base ref may be put at
+ * any time due to an attribute change. Pin @pwq until the
+ * rescuer is done with it.
+ */
+ get_pwq(pwq);
list_add_tail(&pwq->mayday_node, &wq->maydays);
wake_up_process(wq->rescuer->task);
}
@@ -2450,6 +2456,12 @@ repeat:
process_scheduled_works(rescuer);
/*
+ * Put the reference grabbed by send_mayday(). @pool won't
+ * go away while we're holding its lock.
+ */
+ put_pwq(pwq);
+
+ /*
* Leave this pool. If keep_working() is %true, notify a
* regular worker; otherwise, we end up with 0 concurrency
* and stalling the execution.