Subj : Re: Real cause of spurious wakeups
To   : comp.programming.threads
From : David Hopwood
Date : Thu Mar 31 2005 09:55 pm

Alexander Terekhov wrote:
> Vladimir Prus wrote:
> 
>>can somebody explain the real reason why spurious wakeups are possible. That
>>is, why call to pthread_cond_wait can return without
>>pthread_cond_broadcast/pthread_cond_signal. 
> 
> Because apart from realtime scheduling, 
> pthread_cond_broadcast/pthread_cond_signal can be implemented as nop.
> 
> No kidding. 
> 
>   cond_wait: mutex::release_guard guard(mutex); sleep(random());
> 
>   cond_signal: nop
> 
>   cond_broadcast: nop

This is a very inefficient implementation that would not be used in practice,
so it doesn't answer the OP's question.

-- 
David Hopwood <david.nospam.hopwood@blueyonder.co.uk>

.