Date: Wed, 10 Feb 2010 13:49:04 -0500 (EST) From: Daniel Eischen <deischen@freebsd.org> To: Randall Stewart <rrs@lakerest.net> Cc: threads@freebsd.org Subject: Re: Thinking about kqueue's and pthread_cond_wait Message-ID: <Pine.GSO.4.64.1002101331240.14115@sea.ntplx.net> In-Reply-To: <07AA24BB-DA26-406A-B24F-59E0CB36FEBE@lakerest.net> References: <3581A86D-9C9C-4E08-9AD3-CD550B180CED@lakerest.net> <Pine.GSO.4.64.1002101202060.13656@sea.ntplx.net> <3CF3033E-FD13-405B-9DC6-DDE9DF4FBF37@lakerest.net> <Pine.GSO.4.64.1002101232240.13876@sea.ntplx.net> <07AA24BB-DA26-406A-B24F-59E0CB36FEBE@lakerest.net>
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On Wed, 10 Feb 2010, Randall Stewart wrote:
>
>
> while (notdone) {
> nev = kevent(kq, , ev);
> if (ev.fitler == EVFILTER_READ) {
> handle_the_read_thingy(ev);
> } else if (ev.filter == EVFILTER_COND) {
> lock_mutex(if needed)
> handle_condition_event();
> }
> }
>
>
> One of the things I will note about a condition variable is that the downside
> is
> you ALWAYS have to have a mutex.. and not always do you need one... I have
> found
> multiple times in user apps where i am creating a mutex only for the benefit
> of
> the pthread_cond() api... sometimes just being woken up is enough ;-)
[ I didn't see that you were waiting on multiple CVs... ]
I don't understand why you need to wait on multiple
condition variables. Either way, you have to maintain
a queue of them along with their associated mutexes and
then take some action unique to each one of them. What
is the difference between that and maintaining a queue of
some other thingies that maintain similar state data?
--
DE
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