Date: Wed, 17 Jan 2001 11:41:58 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: Alfred Perlstein <bright@wintelcom.net> Cc: arch@FreeBSD.org, Matt Dillon <dillon@earth.backplane.com> Subject: Re: HEADS-UP: await/asleep removal imminent Message-ID: <XFMail.010117114158.jhb@FreeBSD.org> In-Reply-To: <20010117112850.X7240@fw.wintelcom.net>
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On 17-Jan-01 Alfred Perlstein wrote:
>
> Jason Evans just added his conditional variables, you could change
> asleep/await into cv_attach/cv_await or something, that would give
> you less contention on the sleep/run queues, but you'd still need
> a spinlock or mutex on these variables.
A condvar already contains the state information that asleep() caches in
p_aleep right now, so just passing condvar pointers around would accomplish
this task using an existing API and is conceptually cleaner:
int
my_lowlevel_func(struct cv **cv)
{
if (bad_things) {
*cv = &my_condition;
return (some_error);
}
*cv = NULL;
return (0);
}
...
struct cv *cv;
...
if (my_lowlevel_func(&cv) != 0) {
KASSERT(cv != NULL, (__FUNCTION__ ": nothing to sleep on!"));
cv_wait(cv);
}
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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