threads/150889: PTHREAD_MUTEX_INITIALIZER + pthread_mutex_destroy() == EINVAL

[Jilles Tjoelker]

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