Date: Mon, 5 Feb 2001 07:56:39 -0500 (EST) From: Daniel Eischen <eischen@vigrid.com> To: "Paul D. Schmidt" <pds@uberhacker.org> Cc: hackers@FreeBSD.ORG Subject: Re: known pthread bug? Message-ID: <Pine.SUN.3.91.1010205074310.10833A-100000@pcnet1.pcnet.com> In-Reply-To: <20010204232301.C30977@uberhacker.org>
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On Sun, 4 Feb 2001, Paul D. Schmidt wrote:
> Are there currently any known bugs with pthread_mutex_init
> and pthread_cond_init returning 0, but pthread_cond_wait
> returning EINVAL nonetheless?
Yes, it's a known bug with the _application_ ;-)
pthread_cond_[timed]wait must be called with a mutex and that
must be the only mutex used with that condition variable. For
instance:
pthread_mutex_t m1, m2;
pthread_cond_t cv;
thread 1:
pthread_mutex_lock(&m1);
ret = pthread_cond_wait(&cv, &m1);
pthread_mutex_unlock(&m1);
thread 2:
pthread_mutex_lock(&m2);
ret = pthread_cond_wait(&cv, &m2);
pthread_mutex_unlock(&m2);
can result in one of the threads returning EINVAL from
pthread_cond_wait if one thread is already waiting on the
condition variable when the other thread calls pthread_cond_wait().
There is no problem if only one thread is waiting on the
condition variable at any one time, but that still should
be avoided.
--
Dan Eischen
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