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Date: Thu, 20 Mar 2008 17:34:06 +0800
From: David Xu <davidxu@FreeBSD.org>
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To: Jeff Roberson <jroberson@chesapeake.net>
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Cc: cvs-src@FreeBSD.org, Jeff Roberson <jeff@FreeBSD.org>,
	src-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/kern subr_sleepqueue.c
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Jeff Roberson wrote:
> 
> On Tue, 18 Mar 2008, Jeff Roberson wrote:
> 
>> On Wed, 19 Mar 2008, David Xu wrote:
>>
>>> Jeff Roberson wrote:
>>>> jeff        2008-03-19 07:35:14 UTC
>>>>
>>>>   FreeBSD src repository
>>>>
>>>>   Modified files:
>>>>     sys/kern             subr_sleepqueue.c   Log:
>>>>    - At the top of sleepq_catch_signals() lock the thread and check 
>>>> TDF_NEEDSIGCHK
>>>>      before doing the very expensive cursig() and related locking. 
>>>> NEEDSIGCHK
>>>>      is updated whenever our signal mask change or when a signal is 
>>>> delivered and
>>>>      should be sufficient to avoid the more expensive tests.  This 
>>>> eliminates
>>>>      another source of PROC_LOCK contention in multithreaded programs.
>>>>     Revision  Changes    Path
>>>>   1.50      +12 -4     src/sys/kern/subr_sleepqueue.c
>>>>
>>>
>>> This may break process suspension, a more completed patch is here: 
>>> (though it is outdated):
>>>
>>> http://people.freebsd.org/~davidxu/patch/PCATCH_optimize.patch
>>>
>>> In one word, process suspending may be in progress, and the thread
>>> should check it.
>>
>> Thanks Xu.  I will add your NEEDSUSPCHECK flag and check that as well.
> 
> http://people.freebsd.org/~jeff/suspchk.diff
> 
> Can you review this diff?  I rely on ast() to check and clear the flag 
> as we do with NEEDSIGCHK.  I removed the check from userret() as we 
> don't need to do it every time now.
> 
> Thanks,
> Jeff
> 

It looks okay to me, the code looks more clean than KSE time.

Regards,
David Xu