From: Tejun Heo <tj@kernel.org>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/7 V2] workqueue: reuse the current default pwq when its attrs unchanged
Date: Mon, 18 May 2015 16:38:09 -0400 [thread overview]
Message-ID: <20150518203809.GF24861@htj.duckdns.org> (raw)
In-Reply-To: <1431433955-3173-6-git-send-email-laijs@cn.fujitsu.com>
Hello,
On Tue, May 12, 2015 at 08:32:33PM +0800, Lai Jiangshan wrote:
> When apply_wqattrs_prepare() is called, it is possible that the default
> pwq is unaffected. It is always true that only the NUMA affinity is being
> changed and sometimes true that the low level cpumask is being changed.
>
> So we try to reuse the current default pwq when its attrs unchanged.
>
> After this change, "ctx->dfl_pwq->refcnt++" could be dangerous
> when ctx->dfl_pwq is being reused, so we use get_pwq_unlocked() instead.
Can you elaborate the above paragraph? Why wouldn't that be dangerous
before this change?
Thanks.
--
tejun
next prev parent reply other threads:[~2015-05-18 20:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-12 12:32 [PATCH 0/7 V2] workqueue: cleanup for attr management Lai Jiangshan
2015-05-12 12:32 ` [PATCH 1/7 V2] workqueue: wq_pool_mutex protects the attrs-installation Lai Jiangshan
2015-05-12 12:32 ` [PATCH 2/7 V2] workqueue: simplify wq_update_unbound_numa() Lai Jiangshan
2015-05-18 20:21 ` Tejun Heo
2015-05-12 12:32 ` [PATCH 3/7 V2] workqueue: introduce get_pwq_unlocked() Lai Jiangshan
2015-05-18 20:28 ` Tejun Heo
2015-05-18 20:41 ` Tejun Heo
2015-05-12 12:32 ` [PATCH 4/7 V2] workqueue: reuse the current per-node pwq when its attrs unchanged Lai Jiangshan
2015-05-18 20:34 ` Tejun Heo
2015-05-25 9:47 ` Lai Jiangshan
2015-05-26 18:51 ` Tejun Heo
2015-05-12 12:32 ` [PATCH 5/7 V2] workqueue: reuse the current default " Lai Jiangshan
2015-05-18 20:38 ` Tejun Heo [this message]
2015-05-12 12:32 ` [PATCH 6/7 V2] workqueue: reuse wq_update_unbound_numa_attrs_buf as temporary attrs Lai Jiangshan
2015-05-12 12:32 ` [PATCH 7/7 V2] workqueue: add get_node_unbound_pwq() Lai Jiangshan
2015-05-18 0:39 ` [PATCH 0/7 V2] workqueue: cleanup for attr management Lai Jiangshan
2015-05-18 1:26 ` Tejun Heo
2015-05-18 2:06 ` Lai Jiangshan
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