[ECOS] pthread_mutex_unlock when mutex is not locked

Rubén Pérez de Aranda Alonso rperez@sidsa.es
Wed Apr 27 09:54:00 GMT 2005

I think the mutex is appropiate for the explained scenario.

The standard says:
"If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains 
the concept of a lock count. When a thread successfully acquires a mutex 
for the first time, the lock count is set to one. Every time a thread 
relocks this mutex, the lock count is incremented by one. Each time the 
thread unlocks the mutex, the lock count is decremented by one. When the 
lock count reaches zero, the mutex becomes available for other threads 
to acquire. If a thread attempts to unlock a mutex that it has not 
locked or a mutex which is unlocked, an error will be returned."


So, I think the unlock method must return an error code. In eCOS, this
method returns void. If we check the mutex is locked at least we avoided the
crash of the system.


Sergei Organov wrote:

>RubИn PИrez de Aranda Alonso <rperez@sidsa.es> writes:
>>Hi all,
>>I have found a problem when I want to unlock a mutex that is not locked
>>by any thread.
>Then the problem is in your code. The mutex is not appropriate for what
>you are doing, -- only the thread that locked the mutex is allowed to
>unlock it. Use something else, e.g., semaphore or condition variable to
>achieve your goal.


Rubén Israel Pérez de Aranda Alonso
SIDSA - Semiconductores Investigación y Diseño S.A.
Parque Tecnológico de Madrid           Phone : +34 91 803 5052
C/ Torres Quevedo, nº 1                Fax:    +34 91 803 9557
28760 TRES CANTOS (Madrid) (SPAIN)
e-mail: rperez@sidsa.com               www.sidsa.com

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