From: Lai Jiangshan <laijs@cn.fujitsu.com>
To: Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Subject: [PATCH 1/9 V3] workqueue: ensure the wq_worker_sleeping() see the right flags
Date: Thu, 30 Aug 2012 00:51:52 +0800 [thread overview]
Message-ID: <1346259120-6216-2-git-send-email-laijs@cn.fujitsu.com> (raw)
In-Reply-To: <1346259120-6216-1-git-send-email-laijs@cn.fujitsu.com>
The compiler may compile this code into TWO write/modify instructions.
worker->flags &= ~WORKER_UNBOUND;
worker->flags |= WORKER_REBIND;
so the other CPU may see the temporary of worker->flags which has
not WORKER_UNBOUND nor WORKER_REBIND, it will wrongly do local wake up.
so we use one write/modify instruction explicitly instead.
This bug will not occur on idle workers, because they have another
WORKER_NOT_RUNNING flags.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
kernel/workqueue.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 692d976..4f252d0 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1434,10 +1434,13 @@ retry:
/* rebind busy workers */
for_each_busy_worker(worker, i, pos, gcwq) {
struct work_struct *rebind_work = &worker->rebind_work;
+ unsigned long worker_flags = worker->flags;
/* morph UNBOUND to REBIND */
- worker->flags &= ~WORKER_UNBOUND;
- worker->flags |= WORKER_REBIND;
+ worker_flags &= ~WORKER_UNBOUND;
+ worker_flags |= WORKER_REBIND;
+ /* ensure the wq_worker_sleeping() see the right flags */
+ ACCESS_ONCE(worker->flags) = worker_flags;
if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
work_data_bits(rebind_work)))
--
1.7.4.4
next prev parent reply other threads:[~2012-08-29 16:50 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-29 16:51 [PATCH 0/9 V3] workqueue: fix and cleanup hotplug/rebind_workers() Lai Jiangshan
2012-08-29 16:51 ` Lai Jiangshan [this message]
2012-08-29 16:51 ` [PATCH 2/9 V3] workqueue: fix deadlock in rebind_workers() Lai Jiangshan
2012-08-29 16:51 ` [PATCH 3/9 V3] workqueue: add POOL_MANAGING_WORKERS Lai Jiangshan
2012-08-29 18:21 ` Tejun Heo
2012-08-30 2:38 ` Lai Jiangshan
2012-08-29 16:51 ` [PATCH 4/9 V3] workqueue: add non_manager_role_manager_mutex_unlock() Lai Jiangshan
2012-08-29 18:25 ` Tejun Heo
2012-08-30 9:16 ` Lai Jiangshan
2012-08-30 9:17 ` Tejun Heo
2012-08-31 1:08 ` Lai Jiangshan
2012-08-29 16:51 ` [PATCH 5/9 V3] workqueue: move rebind_hold to idle_rebind Lai Jiangshan
2012-08-29 16:51 ` [PATCH 6/9 V3] workqueue: simple clear WORKER_REBIND Lai Jiangshan
2012-08-29 16:51 ` [PATCH 7/9 V3] workqueue: explicit way to wait for idles workers to finish Lai Jiangshan
2012-08-29 18:34 ` Tejun Heo
2012-08-29 16:51 ` [PATCH 8/9 V3] workqueue: single pass rebind_workers Lai Jiangshan
2012-08-29 18:40 ` Tejun Heo
2012-08-29 16:52 ` [PATCH 9/9 V3] workqueue: merge the role of rebind_hold to idle_done Lai Jiangshan
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