Re: [boost] Probably bug in condition::timed_wait()

From: Peter Dimov (pdimov_at_[hidden])
Date: 2006-10-09 14:31:21

Alexander Terekhov wrote:
> Peter Dimov wrote:
> [...]
>>> Another possible fix is to broadcast() (signal() is not enough).
>>> 
>>> while (!pred()) { if (!timed_wait(lock, xt)) return broadcast(),
>>> false; }
>> 
>> Ummmm.... why is signal() not enough?
> 
> Threads A and B waiting (A does timed wait), C changes something,
> signals and enters wait expecting another state change followed by
> signaling from either A or B (whichever gets the signal and makes
> processing). If A times out and only re-signal, that signal can be
> consumed by C as spurious wake. So broadcast() is needed to wake B
> and let it do the job.

Terrific. Thanks Alexander.