Re: [boost] [Interprocess::Semaphore] Deadlock on more producers - one consumer problem

Subject: Re: [boost] [Interprocess::Semaphore] Deadlock on more producers - one consumer problem
From: Zachary Turner (divisortheory_at_[hidden])
Date: 2009-06-20 18:16:30

2009/6/20 Ion Gaztañaga <igaztanaga_at_[hidden]>:
> Zachary Turner wrote:
>
>> Sorry for jumping into the middle of this.  But shouldn't it only
>> notify_one() if count is greater than or equal to 0?  Not
>> unconditionally.  It's possible to initialize the semaphore with a
>> negative count, and in that case a call to wait() should not unblock
>> until the semaphore is 0 or higher.
>
> Ummm... Interprocess models POSIX primitives and I see that
>
> #include <semaphore.h>
>
> int sem_init(sem_t *sem, int pshared, unsigned int value);
>
> semaphore value should be always positive, something that does not happen in
> Interprocess:
>
> interprocess_semaphore(int initialCount);
>
> So I think I should change interprocess constructor to an unsigned int.
>

That works too :)  Just out of curiosity why doesn't windows backend
just use built-in windows api functions for manipulating semaphores?
CreateSemaphore, etc?  I haven't done any performance benchmarks
myself, but it seems like using native system calls would be faster
and more scalable.