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Date:      Thu, 23 Sep 2010 23:07:46 +0200
From:      Jilles Tjoelker <jilles@stack.nl>
To:        Christopher Faylor <cgf@netapp.com>
Cc:        freebsd-gnats-submit@freebsd.org, freebsd-threads@freebsd.org
Subject:   Re: threads/150889: PTHREAD_MUTEX_INITIALIZER + pthread_mutex_destroy() == EINVAL
Message-ID:  <20100923210746.GA44173@stack.nl>
In-Reply-To: <1285270911.11313.30.camel@trixie.casa.cgf.cx>
References:  <201009231733.o8NHXuao082524@www.freebsd.org> <201009231414.50271.jhb@freebsd.org> <1285270911.11313.30.camel@trixie.casa.cgf.cx>

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On Thu, Sep 23, 2010 at 03:41:51PM -0400, Christopher Faylor wrote:
> I don't see how this represents buggy code.  It should be possible to
> destroy a mutex which is allocated statically.  Currently, if a mutex is
> assigned to PTHREAD_MUTEX_INITIALIZER and then used once, it can be
> successfully destroyed.  It is only receive an EINVAL when there has
> been no intervening call to any mutex function.  I don't think that a
> PTHREAD_MUTEX_INITIALIZER using program should have to check for that.

One may want to destroy a mutex to help memory leak checkers and detect
bugs, and then this is indeed a problem.

> However, regardless, this is still a bug in pthread_mutex_destroy right?

It is inconsistent at best.

It seems best to make the proposed change. This will allow
pthread_mutex_destroy() on a destroyed mutex to succeed (which used to
return EINVAL), but pthread_mutex_lock() already succeeded as well
(initializing the mutex in the process).

If/when pthread_mutex_t is made a struct, this can be revisited, and
most likely the destroyed and PTHREAD_MUTEX_INITIALIZER states will be
different (PTHREAD_MUTEX_INITIALIZER will likely be a normal state that
does not need special initialization to use).

-- 
Jilles Tjoelker



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