-=> Quoting Mario Semo to Phil Crown <=-

 MS> class RequestMutex
 MS> {
 MS> public:
 MS> RequestMutex(Mutex & mutex) : mutex(mutex) { mutex.request();}
 MS> ~RequestMutex() { mutex.release();}
 MS> private:
 MS> Mutex mutex;
 MS> };

 MS> function()
 MS> {
 MS> RequestMutex request(mutex);
 MS> call someone();
 MS> return rc;
 MS> };

 MS> now, request is a local object, and when an exception is thrown, ALL
 MS> local (stack based) objects get destroyed! so, ~RequestMutex is called
 MS> and the sema4 is released.  
 MS> Servus, Mario!

Neat trick!

But, is the overhead of creating the mutex semaphore trivial?  My code
has two threads calling this semaphore VERY often.

Also, say one thread has created the sem and is pre-empted before
deleteing it, what happens when the second thread tries to create a sem
with the same name?  Error code or exception or blocks until the first
thread deletes the sem?

Phil Crown
pcrown{at}airmail.net
http://web2.airmail.net/pcrown/

--- Blue Wave/OS2 v2.30