pthread_mutex_trylock() should never block
Daniel Eischen
eischen at vigrid.com
Wed Jan 28 09:01:39 PST 2004
On Wed, 28 Jan 2004, Mike Makonnen wrote:
> On Sun, Dec 07, 2003 at 01:34:31AM -0500, Daniel Eischen wrote:
> >
> > The man page may not mention it, and that may be a bug, but I
> > think a pthread_mutex_trylock() on a non-recursive mutex is allowed
> > to return EDEADLK.
> >
> > http://www.opengroup.org/onlinepubs/007904975/functions/pthread_mutex_trylock.html
> >
> > If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error
> > checking shall be provided. If a thread attempts to relock a
> > mutex that it has already locked, an error shall be returned.
> > If a thread attempts to unlock a mutex that it has not locked
> > or a mutex which is unlocked, an error shall be returned.
> >
> > ...
>
> If you look further down in the spec you will see:
>
> The pthread_mutex_trylock() function shall be equivalent to
> pthread_mutex_lock(), except that if the mutex object referenced
> by mutex is currently locked (by any thread, including
> the current thread), the call shall return immediately...
Yes, but the implementation has to use internal locks to
keep the mutex in a consistent state. There is no problem
here.
--
Dan Eischen
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