Date: Tue, 4 Nov 2008 14:51:57 -0800 From: "Peter Wemm" <peter@wemm.org> To: "John Baldwin" <jhb@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, David Xu <davidxu@freebsd.org> Subject: Re: svn commit: r184216 - head/sys/kern Message-ID: <e7db6d980811041451w1da54fa3lceeed73a640f51a0@mail.gmail.com> In-Reply-To: <200811041707.26052.jhb@freebsd.org> References: <200810240103.m9O13V7f071075@svn.freebsd.org> <200811041707.26052.jhb@freebsd.org>
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On Tue, Nov 4, 2008 at 2:07 PM, John Baldwin <jhb@freebsd.org> wrote: > On Thursday 23 October 2008 09:03:31 pm David Xu wrote: >> Author: davidxu >> Date: Fri Oct 24 01:03:31 2008 >> New Revision: 184216 >> URL: http://svn.freebsd.org/changeset/base/184216 >> >> Log: >> partly revert revision 184199, because TDF_NEEDSIGCHK is persitent >> when thread is in kernel mode, it can cause dead loop, now unlock >> process lock after acquired sleep queue lock and thread lock to >> avoid the problem. This means TDF_NEEDSIGCHK and TDF_NEEDSUSPCHK must >> be set with process lock and thread lock being hold at same time. > > You can't unlock the proc lock while holding the thread_lock(). This will > lead to deadlock due to the way that thread_lock() works. This is different > from the rules in 6.x where you could drop a mutex while holding sched_lock. > You will need to revert this. > > -- > John Baldwin I had to back out rev 184216 and 184199 in total in order to stop my machine from dying. Compile this dumb program: http://people.freebsd.org/~peter/pth.c $ cc -pthread -o pth pth.c run in a shell while loop so that the entire thing is execed and exits repeatedly. $ while true; do date; ./pth; done On my 2-core athlon64 box at home, and the 8-core ref8-i386 in the freebsd.org cluster, this causes a lockup in mere seconds. Backing out these two changes solves it. my machine: spin lock 0xffffff00a4037000 (turnstile lock) held by 0xffffff01045746e0 (tid 100355) too long panic: spin lock held too long ref8-i386: spin lock 0xc06436c0 (sched lock 5) held by 0xd374f690 (tid 100249) too long panic: spin lock held too long -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV "All of this is for nothing if we don't go to the stars" - JMS/B5 "If Java had true garbage collection, most programs would delete themselves upon execution." -- Robert Sewell
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