[PATCH 5.4 087/102] workqueue: Add RCU annotation for pwq list walk

Greg Kroah-Hartman
2020-01-24T09:41:48Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

[ Upstream commit 49e9d1a9faf2f71fdfd80a30697ee9a15070626d ]

An additional check has been recently added to ensure that a RCU related lock
is held while the RCU list is iterated.
The `pwqs' are sometimes iterated without a RCU lock but with the &wq->mutex
acquired leading to a warning.

Teach list_for_each_entry_rcu() that the RCU usage is okay if &wq->mutex
is acquired during the list traversal.

Fixes: 28875945ba98d ("rcu: Add support for consolidated-RCU reader checking")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/workqueue.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 649687622654b..e9c63b79e03f4 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -425,7 +425,8 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
* ignored.
*/
#define for_each_pwq(pwq, wq) \
- list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
+ list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
+ lockdep_is_held(&wq->mutex)) \
if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
else

--
2.20.1