apr-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Aaron Bannert <aa...@clove.org>
Subject Re: remove nested mutexes?
Date Fri, 12 Sep 2003 05:11:06 GMT

On Thursday, September 11, 2003, at 10:02  PM, Greg Stein wrote:
> I've written applications like this. One thread will create a mutex, 
> stash
> that away in a global, or somesuch, and then lock the thing *twice*. 
> When
> another thread wants the first one to resume, it unlocks the mutex.

Eeww, that's not what mutexes were designed to do, and there are cases
where that will fail (specifically, if you try to do that with multiple
threads, you don't at all get fair scheduling for the threads blocking
behind that mutex.)

> If we have another way for a thread to block, then have another thread 
> say
> "okay. go ahead and proceed", then I'm all for removing nested mutexes.

Yeah, that's totally what condition variables are for, and IIRC we have
those implemented across all APR-supported platforms.


View raw message