Re: [Qemu-devel] [patch 1/2] qemu: sem/thread helpers

[Paul Brook]

On Tuesday 17 March 2009, Marcelo Tosatti wrote:
> On Sun, Mar 15, 2009 at 04:15:52PM +0200, Avi Kivity wrote:
> > Marcelo Tosatti wrote:
> >> +
> >> +struct QemuSem {
> >> +    sem_t sema;
> >> +};
> >
> > Why aren't you using pthread_mutex_t?
>
> Because we want the thread waiting on the lock to be awakened
> once the holder releases it. This does not happen with pthread
> mutexes AFAIK.

Really? I'd be surprised if there's any difference. The whole point of a mutex 
is that it blocks until the other thread releases it.  At best it sounds like 
you're making fairly sketchy assumptions about the host OS scheduler 
heuristics.

Paul