From: Tejun Heo <tj@kernel.org>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/11 V5] workqueue: new day don't need WORKER_REBIND for busy rebinding
Date: Wed, 5 Sep 2012 11:31:48 -0700 [thread overview]
Message-ID: <20120905183148.GB13737@google.com> (raw)
In-Reply-To: <1346841475-4422-4-git-send-email-laijs@cn.fujitsu.com>
On Wed, Sep 05, 2012 at 06:37:40PM +0800, Lai Jiangshan wrote:
> because old busy_worker_rebind_fn() have to wait until all idle worker finish.
> so we have to use two flags WORKER_UNBOUND and WORKER_REBIND to avoid
> prematurely clear all NOT_RUNNING bit when highly frequent offline/online.
>
> but current code don't need to wait idle workers. so we don't need to
> use two flags, just one is enough. remove WORKER_REBIND from busy rebinding.
ROGUE / REBIND thing existed for busy workers from the beginning when
there was no idle worker rebinding, so this definitely wasn't about
whether idle rebind is synchronous or not. Trying to remember
what... ah, okay, setting of DISASSOCIATED and setting of WORKER_ROGUE
didn't use to happen together with gcwq->lock held. CPU_DOWN would
first set ROGUE and then later on set DISASSOCIATED, so if the
rebind_fn kicks in inbetween that, it would break CPU_DOWN.
I think now that both CPU_DOWN and UP are done under single holding of
gcwq->lock, this should be safe. It would be nice to note what
changed in the patch description and the atomicity requirement as a
comment tho.
Thanks.
--
tejun
next prev parent reply other threads:[~2012-09-05 18:31 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-05 10:37 [PATCH 00/11 V5] workqueue: reimplement unbind/rebind Lai Jiangshan
2012-09-05 10:37 ` [PATCH 01/11 V5] workqueue: ensure the wq_worker_sleeping() see the right flags Lai Jiangshan
2012-09-05 10:37 ` [PATCH 02/11 V5] workqueue: async idle rebinding Lai Jiangshan
2012-09-05 18:06 ` Tejun Heo
2012-09-06 1:28 ` Lai Jiangshan
2012-09-05 10:37 ` [PATCH 03/11 V5] workqueue: new day don't need WORKER_REBIND for busy rebinding Lai Jiangshan
2012-09-05 18:31 ` Tejun Heo [this message]
2012-09-06 2:10 ` Lai Jiangshan
2012-09-05 10:37 ` [PATCH 04/11 V5] workqueue: remove WORKER_REBIND Lai Jiangshan
2012-09-05 10:37 ` [PATCH 05/11 V5] workqueue: Add @bind arguement back without change any thing Lai Jiangshan
2012-09-05 19:49 ` Tejun Heo
2012-09-06 1:04 ` Lai Jiangshan
2012-09-06 16:51 ` Tejun Heo
2012-09-07 2:11 ` Lai Jiangshan
2012-09-07 19:37 ` Tejun Heo
2012-09-05 10:37 ` [PATCH 06/11 V5] workqueue: unbind manager Lai Jiangshan
2012-09-05 10:37 ` [PATCH 07/11 V5] workqueue: rebind manager Lai Jiangshan
2012-09-05 10:37 ` [PATCH 08/11 V5] workqueue: unbind newly created worker Lai Jiangshan
2012-09-05 10:37 ` [PATCH 09/11 V5] workqueue: rebind " Lai Jiangshan
2012-09-05 16:19 ` Lai Jiangshan
2012-09-05 10:37 ` [PATCH 10/11 V5] workqueue: unbind/rebind without manager_mutex Lai Jiangshan
2012-09-05 20:04 ` Tejun Heo
2012-09-06 10:44 ` Lai Jiangshan
2012-09-06 17:00 ` Tejun Heo
2012-09-05 10:37 ` [PATCH 11/11 V5] workqueue: remove manager_mutex Lai Jiangshan
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