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Date: Thu, 23 Feb 2012 08:07:49 +0800
From: David Xu <listlog2011@gmail.com>
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To: Jilles Tjoelker <jilles@stack.nl>
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Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
	src-committers@FreeBSD.org, David Xu <davidxu@FreeBSD.org>
Subject: Re: svn commit: r231989 - in head: lib/libthr/thread sys/kern
	sys/sys
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On 2012/2/23 7:42, Jilles Tjoelker wrote:
> On Wed, Feb 22, 2012 at 03:22:50AM +0000, David Xu wrote:
>> Author: davidxu
>> Date: Wed Feb 22 03:22:49 2012
>> New Revision: 231989
>> URL: http://svn.freebsd.org/changeset/base/231989
>> Log:
>>    Use unused fourth argument of umtx_op to pass flags to kernel for operation
>>    UMTX_OP_WAIT. Upper 16bits is enough to hold a clock id, and lower
>>    16bits is used to pass flags. The change saves a clock_gettime() syscall
>>    from libthr.
>> Modified:
>>    head/lib/libthr/thread/thr_umtx.c
>>    head/sys/kern/kern_umtx.c
>>    head/sys/sys/umtx.h
>>
>> Modified: head/lib/libthr/thread/thr_umtx.c
>> ==============================================================================
>> --- head/lib/libthr/thread/thr_umtx.c	Wed Feb 22 01:50:13 2012	(r231988)
>> +++ head/lib/libthr/thread/thr_umtx.c	Wed Feb 22 03:22:49 2012	(r231989)
>> @@ -200,20 +200,10 @@ int
>> +	       	abstime != NULL ? (void *)(uintptr_t)((clockid<<  16) | UMTX_WAIT_ABSTIME) : 0,
> Please check that this shift does not lose any information (i.e.,
> clockid>= 0&&  clockid<= 0xFFFF) before doing it.
>
> Implementing clock_getcpuclockid() will require clockids greater than
> 65535 because such clockids contain a process id.
>
In which document said the clock id includes a process id ? I think the 
clock_getcpuclockid()
is a simplified version of getrusage().