linux-kernel - Re: poll: allow f_op->poll to sleep, take #3

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Message-ID: <20081123085902.GI30453@elte.hu>
Date:	Sun, 23 Nov 2008 09:59:02 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	Tejun Heo <htejun@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Wilcox <matthew@....cx>,
	Miklos Szeredi <miklos@...redi.hu>, arjan@...ux.intel.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	hch@...radead.org, rminnich@...dia.gov, ericvh@...il.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: poll: allow f_op->poll to sleep, take #3


* Davide Libenzi <davidel@...ilserver.org> wrote:

> On Sun, 23 Nov 2008, Tejun Heo wrote:
> 
> > +static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
> > +{
> > +	struct poll_wqueues *pwq = wait->private;
> > +	DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
> > +
> > +	set_mb(pwq->triggered, 1);
> > +
> > +	/* perform the default wake up operation */
> > +	return default_wake_function(&dummy_wait, mode, sync, key);
> > +}
> 
> Wouldn't it be nicer to un-static try_to_wake_up() (or a wrapper) 
> instead of setting up a fake wait queue just to use 
> default_wake_function(), just to wake up a task?

the already existing single-task-wakeup shortcut method made available 
by the scheduler is wake_up_process(). A number of primitives where 
waitqueue overhead is of concern already make use of it. 
(mutexes/rtmutexes and more)

if you need a different mode flag, then please extend the 
wake_up_process() family of APIs.

	Ingo
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