Subj : Re: Can you limit the number of Posts to a POSIX semaphore?
To   : comp.programming.threads
From : Frank J. Lhota
Date : Wed Aug 10 2005 02:36 pm

the_edge123.nospam@club-internet.fr wrote:
> Frank J. Lhota a écrit :
> 
> 
>>I'm looking into porting a Win32 program to Linux. This program makes
>>use of the fact that a Win32 semaphore is created with both an initial
>>value and a maximum value. For example,
>>
>>     hSem = CreateSemaphore (NULL, 1, 3, NULL);
>>
>>creates a semaphore with an initial value of 1 and a maximum value of 3.
>>If ReleaseSemaphore (the Win32 version of sem_post) is called for hSem
>>when its value is already equal to 3, then ReleaseSemaphore fails with
>>an error code of ERROR_TOO_MANY_POSTS, and the value of hSem is not
>>incremented.
>>
>>Is there an easy way to do this with POSIX semaphores? AFAICT there is a
>>  fairly large, system-wide upper limit on the value of a POSIX sem_t
>>value. What I am looking for is something that works like sem_t, except
>>that we can set an upper limit (other than SEM_VALUE_MAX) on the value
>>of the semaphore.
>>
>>Any help would be most appreciated.
>>
> 
> You may use sem_getvalue...

I could, but it seems quite likely that I would introduce a race condition.



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