Hello, Linus.
CPU hotplug callbacks can invoke DOWN_FAILED w/o preceding
DOWN_PREPARE which can trigger a WARN_ON() in workqueue. The bug has
been there for a very long time. It only triggers if CPU down fails
at a specific point and I don't think it has adverse effects other
than the warning messages. The fix is very low impact.
Thanks.
The following changes since commit 346c09f80459a3ad97df1816d6d606169a51001a:
workqueue: fix ghost PENDING flag while doing MQ IO (2016-04-26 11:23:22
-0400)
are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-4.6-fixes
for you to fetch changes up to f7c17d26f43d5cc1b7a6b896cd2fa24a079739b9:
workqueue: fix rebind bound workers warning (2016-05-12 12:00:23 -0400)
----------------------------------------------------------------
Wanpeng Li (1):
workqueue: fix rebind bound workers warning
kernel/workqueue.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 801a698..1b2e36b 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4555,6 +4555,17 @@ static void rebind_workers(struct worker_pool *pool)
pool->attrs->cpumask) < 0);
spin_lock_irq(&pool->lock);
+
+ /*
+ * XXX: CPU hotplug notifiers are weird and can call DOWN_FAILED
+ * w/o preceding DOWN_PREPARE. Work around it. CPU hotplug is
+ * being reworked and this can go away in time.
+ */
+ if (!(pool->flags & POOL_DISASSOCIATED)) {
+ spin_unlock_irq(&pool->lock);
+ return;
+ }
+
pool->flags &= ~POOL_DISASSOCIATED;
for_each_pool_worker(worker, pool) {
