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Date: Tue, 28 Sep 2010 23:13:30 -0400 (EDT)
From: Daniel Eischen <deischen@freebsd.org>
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To: David Xu <davidxu@freebsd.org>
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References: <201009280457.o8S4vuS9060037@svn.freebsd.org>
	<201009281202.22555.jkim@FreeBSD.org>
	<201009281220.12278.jkim@FreeBSD.org>
	<201009281829.13253.jkim@FreeBSD.org> <4CA3181E.6030000@freebsd.org>
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
	src-committers@freebsd.org, John Baldwin <jhb@freebsd.org>,
	Jung-uk Kim <jkim@freebsd.org>
Subject: Re: svn commit: r213241 - in head: include lib/libthr/thread
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On Wed, 29 Sep 2010, David Xu wrote:

> Jung-uk Kim wrote:
>> On Tuesday 28 September 2010 12:20 pm, Jung-uk Kim wrote:
[ snip ]
>>> Unfortunately, it seems to have a regression:
>>> 
>>> %cat test.c
>>> #include <pthread.h>
>>> #include <stdio.h>
>>> 
>>> static pthread_cond_t	static_cond = PTHREAD_COND_INITIALIZER;
>>> static pthread_mutex_t	static_mutex = PTHREAD_MUTEX_INITIALIZER;
>>> 
>>> int
>>> main(void)
>>> {
>>>
>>> 	// pthread_mutex_lock(&static_mutex);
>>> 	printf("%d\n", pthread_cond_wait(&static_cond, &static_mutex));
>>> 	pthread_mutex_unlock(&static_mutex);
>>>
>>> 	return (0);
>>> }
>>> %cc -o test test.c -pthread
>>> %./test
>>> Segmentation fault (core dumped)
>>> 
>>> pthread_cond_wait(3) had to return EPERM here. :-(
>> 
>> I realized it is a libthr "feature" to catch real application bugs and to 
>> increase performance by not checking rare conditions, I guess. :-/
>> 
>> Sorry for the noise,
>> 
>> Jung-uk Kim
>> 
> I think your example is legal, I might add checking back, however, it
> would return two codes, EINVAL and EPERM.

By default, I think we should check.  I think PTHREAD_MUTEX_DEFAULT
should be equal to PTHREAD_MUTEX_ERRORCHECK.  So
PTHREAD_MUTEX_INITIALIZER would default to error checking.

I also agree -- if the mutex isn't valid, then return EINVAL,
and if not locked, return EPERM.

-- 
DE