From: Ben Hutchings <ben@decadent.org.uk>
To: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH -stable] workqueue: UNBOUND -> REBIND morphing in rebind_workers() should be atomic
Date: Sun, 16 Sep 2012 16:49:47 +0100 [thread overview]
Message-ID: <1347810587.13258.279.camel@deadeye.wl.decadent.org.uk> (raw)
In-Reply-To: <20120904235812.GA2836@dhcp-172-17-108-109.mtv.corp.google.com>
[-- Attachment #1: Type: text/plain, Size: 1080 bytes --]
On Tue, 2012-09-04 at 16:58 -0700, Tejun Heo wrote:
> From: Lai Jiangshan <laijs@cn.fujitsu.com>
>
> The compiler may compile the following code into TWO write/modify
> instructions.
>
> worker->flags &= ~WORKER_UNBOUND;
> worker->flags |= WORKER_REBIND;
>
> so the other CPU may temporarily see worker->flags which doesn't have
> either WORKER_UNBOUND or WORKER_REBIND set and perform local wakeup
> prematurely.
>
> Fix it by using single explicit assignment via ACCESS_ONCE().
>
> Because idle workers have another WORKER_NOT_RUNNING flag, this bug
> doesn't exist for them; however, update it to use the same pattern for
> consistency.
>
> tj: Applied the change to idle workers too and updated comments and
> patch description a bit.
>
> stable: Idle worker rebinding doesn't apply for -stable and
> WORKER_UNBOUND used to be WORKER_ROGUE. Updated accordingly.
[...]
Added to the queue for 3.2, thanks.
Ben.
--
Ben Hutchings
Experience is what causes a person to make new mistakes instead of old ones.
[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 828 bytes --]
next prev parent reply other threads:[~2012-09-16 15:50 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-01 16:28 [PATCH 00/10 V4] workqueue: fix and cleanup hotplug/rebind_workers() Lai Jiangshan
2012-09-01 16:28 ` [PATCH 01/10 V4] workqueue: ensure the wq_worker_sleeping() see the right flags Lai Jiangshan
2012-09-04 23:39 ` [PATCH] workqueue: UNBOUND -> REBIND morphing in rebind_workers() should be atomic Tejun Heo
2012-09-04 23:58 ` [PATCH -stable] " Tejun Heo
2012-09-16 15:49 ` Ben Hutchings [this message]
2012-09-05 1:05 ` [PATCH] " Lai Jiangshan
2012-09-05 1:17 ` Tejun Heo
2012-09-01 16:28 ` [PATCH 02/10 V4] workqueue: fix deadlock in rebind_workers() Lai Jiangshan
2012-09-05 0:54 ` Tejun Heo
2012-09-05 1:28 ` Lai Jiangshan
2012-09-05 1:33 ` Tejun Heo
2012-09-01 16:28 ` [PATCH 03/10 V4] workqueue: add POOL_MANAGING_WORKERS Lai Jiangshan
2012-09-01 16:28 ` [PATCH 04/10 V4] workqueue: add manage_workers_slowpath() Lai Jiangshan
2012-09-05 1:12 ` Tejun Heo
2012-09-06 1:55 ` Lai Jiangshan
2012-09-01 16:28 ` [PATCH 05/10 V4] workqueue: move rebind_hold to idle_rebind Lai Jiangshan
2012-09-01 16:28 ` [PATCH 06/10 V4] workqueue: simple clear WORKER_REBIND Lai Jiangshan
2012-09-01 16:28 ` [PATCH 07/10 V4] workqueue: move idle_rebind pointer to gcwq Lai Jiangshan
2012-09-01 16:28 ` [PATCH 08/10 V4] workqueue: explicit way to wait for idles workers to finish Lai Jiangshan
2012-09-01 16:28 ` [PATCH 09/10] workqueue: single pass rebind_workers Lai Jiangshan
2012-09-01 16:28 ` [PATCH 10/10 V4] workqueue: merge the role of rebind_hold to idle_done Lai Jiangshan
2012-09-05 1:15 ` Tejun Heo
2012-09-05 1:48 ` Lai Jiangshan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1347810587.13258.279.camel@deadeye.wl.decadent.org.uk \
--to=ben@decadent.org.uk \
--cc=laijs@cn.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=stable@vger.kernel.org \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).