linux-kernel - Re: [PATCH] poll/select: initialize triggered field of struct poll

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Date:	Sun, 16 Aug 2009 09:53:08 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Guillaume Knispel <gknispel@...formatique.com>
CC:	linux-kernel@...r.kernel.org, Miklos Szeredi <mszeredi@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] poll/select: initialize triggered field of struct poll_wqueues

Guillaume Knispel wrote:
> poll/select: initialize triggered field of struct poll_wqueues
> 
> The triggered field of struct poll_wqueues introduced in commit
> 5f820f648c92a5ecc771a96b3c29aa6e90013bba "poll: allow f_op->poll to
> sleep" was set to 1 in pollwake() (now __pollwake() ), tested and
> later set to 0 in poll_schedule_timeout(), but not initialized before.
> As a result when the process needs to sleep, triggered was likely to be
> non-zero even if pollwake() is not called before the first
> poll_schedule_timeout(), meaning schedule_hrtimeout_range() would not
> be called and an extra loop calling all ->poll() would be done.
> 
> This patch initialize triggered to 0 in poll_initwait() so the ->poll()
> are not called twice before the process goes to sleep when it needs to.
> 
> Signed-off-by: Guillaume Knispel <gknispel@...formatique.com>

Ah... nice spotting.

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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