Date: Thu, 27 Aug 2015 20:19:18 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Julien Charbon <jch@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, John Baldwin <jhb@freebsd.org> Subject: Re: svn commit: r286880 - head/sys/kern Message-ID: <20150827171918.GM2072@kib.kiev.ua> In-Reply-To: <55DF3A93.8080507@freebsd.org> References: <201508181015.t7IAFAex055889@repo.freebsd.org> <55DD69E5.4090904@selasky.org> <55DD74EB.30601@selasky.org> <55DE01F7.8040508@freebsd.org> <20150827104946.GH2072@kib.kiev.ua> <55DF3A93.8080507@freebsd.org>
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On Thu, Aug 27, 2015 at 06:28:03PM +0200, Julien Charbon wrote: > > Hi Konstantin, > > On 27/08/15 12:49, Konstantin Belousov wrote: > > On Wed, Aug 26, 2015 at 08:14:15PM +0200, Julien Charbon wrote: > >> As I said, I am not opposed to back out this change, callout(9) API in > >> mpsafe mode is a already complex/subtle API, it won't change too much > >> the current complexity. > >> > >> Let say that if nobody screams until Friday 8/28, I will put back > >> r284245 and revert this change _and_ I will make this case clear in the > >> man page. > > > > [Replying to a random message in the whole set of conversations] > > > > There is one more case, besides TCP timers, which is equially, of not > > more, critical and sensitive WRT to the callout_stop(). Look at the > > sys/kern/subr_sleepqueue.c:sleepq_check_timeout(). Stray return of > > the false result from callout_stop() causes creation of the non-killable > > processes: the callout fired, we missed the wakeup and went to sleep > > by manually doing the context switch. Such thread cannot be woken up. > > > > I suspect that your fix is a better approach than my attempt to look > > at something similar at PR 200992 (may be not). > > This change (r286880) won't improve the PR 200992: > > r286880 only addresses a case where callout_stop() returns 1 instead of > 0. Thus the only thing that can do r286880 to PR 200992: > > - Don't change anything the issues > - Worsen the issue > > Sorry to kill your hope of a simple and elegant fix for PR 200992. Well, not that I am frustrated much. Thank you for taking a look. Did you read the patch attached to the PR ?
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