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

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Message-ID: <492A2DBF.3030208@gmail.com>
Date:	Mon, 24 Nov 2008 13:29:51 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
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

Ingo Molnar wrote:
>> 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.

But it's still being used in quite hot paths (pipe, splice, socket)
and I don't really wanna mix up a change which can cause subtle
scheduling related performance regression into this patch.  How about
using the dummy waitqueue hack for now and when removing the @sync
param, switch it to one of wakeup APIs?  I'll be happy to add big /*
TODO */ comment in the function.

Thanks.

-- 
tejun
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