pthread_mutex_trylock() should never block

Mike Makonnen mtm at
Wed Jan 28 08:50:55 PST 2004

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.
>   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...

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