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

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Date:	Sun, 23 Nov 2008 10:45:51 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tejun Heo <htejun@...il.com>
Cc:	Davide Libenzi <davidel@...ilserver.org>,
	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,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: poll: allow f_op->poll to sleep, take #3


* Tejun Heo <htejun@...il.com> wrote:

> Ingo Molnar wrote:
> > _sync() is not something that should normally be done from poll 
> > handlers. But ->poll() handlers should all be TASK_INTERRUPTIBLE, 
> > right? So wake_up_process_interruptible() should be the thing you 
> > need?
> > 
> > Anyway, if you really want to pass in a state filter, you can use the 
> > already existing wake_up_state() method as well.
> 
> It's not really about what I want but more about how the interface 
> looks in the first place.  Something like the following is simply 
> ugly.
> 
> int my_callback(param a, param b, param c)
> {
> 	WARN_ON(b != B);
> 	do_something(a);
> }
> 
> And @sync might be useful depending on who's waking it up, so we 
> either need to change the wake interface or give it an easier way to 
> pass those parameters as received.  The callback function isn't the 
> right place to ignore those parameters.  It simply doesn't know why 
> the caller is passing them in or what they mean under the 
> circumstances.

We'll likely eliminate the 'sync' parameter from the scheduler. It's 
not a flag that should be proliferated.

	Ingo
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