Date: Fri, 1 Oct 2004 13:08:17 +0200 From: Peter Holm <peter@holm.cc> To: Stephan Uphoff <ups@tree.com> Cc: "freebsd-arch@freebsd.org" <freebsd-arch@FreeBSD.org> Subject: Re: scheduler (sched_4bsd) questions Message-ID: <20041001110817.GA58111@peter.osted.lan> In-Reply-To: <1096603981.21577.195.camel@palm.tree.com> References: <1095468747.31297.241.camel@palm.tree.com> <1096477932.3733.1471.camel@palm.tree.com> <1096489576.3733.1868.camel@palm.tree.com> <200409291652.29990.jhb@FreeBSD.org> <1096496057.3733.2163.camel@palm.tree.com> <1096603981.21577.195.camel@palm.tree.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, Oct 01, 2004 at 12:13:01AM -0400, Stephan Uphoff wrote: > On Wed, 2004-09-29 at 18:14, Stephan Uphoff wrote: > > I was looking at the MUTEX_WAKE_ALL undefined case when I used the > > critical section for turnstile_claim(). > > However there are bigger problems with MUTEX_WAKE_ALL undefined > > so you are right - the critical section for turnstile_claim is pretty > > useless. > > Arghhh !!! > > MUTEX_WAKE_ALL is NOT an option in GENERIC. > I recall verifying that it is defined twice. Guess I must have looked at > the wrong source tree :-( > This means yes - we have bigger problems! > > Example: > > Thread A holds a mutex x contested by Thread B and C and has priority > pri(A). > > Thread C holds a mutex y and pri(B) < pri(C) > > Thread A releases the lock wakes thread B but lets C on the turnstile > wait queue. > > An interrupt thread I tries to lock mutex y owned by C. > > However priority inheritance does not work since B needs to run first to > take ownership of the lock. > > I is blocked :-( > > This was found using Peter Holm's test and a slight modification of this > giant hog detector. (kern_clock.diff) > > I definitely won't have time to fix kern_mutex.c for the next few days > so please add the line: > > options MUTEX_WAKE_ALL # Needed do not remove > I like to test one thing at a time, so I added MUTEX_WAKE_ALL to HEAD from Sep 30 09:58 UTC. This did not seem to change any thing :-( I'll proceed with adding your switch_patch_v2 patch + your sched_4bsd.c patch, but without MUTEX_WAKE_ALL. - Peter > to your configuration files. > > I also had overlooked > http://www.holm.cc/stress/log/cons80.html > Showing that my patch for kern_switch.c (switch_patch) has a bug. > I will send an updated patch later today. > > Stephan > > PS: I love the firewire debugging speed! -- Peter Holm
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20041001110817.GA58111>