Date: Fri, 30 Mar 2001 16:41:41 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: Matthew Jacob <mjacob@feral.com> Cc: current@FreeBSD.org Subject: RE: hmm.... spinlocks.. Message-ID: <XFMail.010330164141.jhb@FreeBSD.org> In-Reply-To: <Pine.BSF.4.21.0103301613300.8467-100000@beppo.feral.com>
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On 31-Mar-01 Matthew Jacob wrote:
>
> On Fri, 30 Mar 2001, John Baldwin wrote:
>
>>
>> On 30-Mar-01 Matthew Jacob wrote:
>> >
>> >
>> > pic_initialize():
>> > lint0: 0x00010700 lint1: 0x00010400 TPR: 0x00000010 SVR: 0x000001ff
>> > kernel trap 12 with interrupts disabled
>> > panic: spin lock sched lock held by 0xc7ba8a60 for > 5 seconds
>> > cpuid = 0; lapic.id = 00000000
>> > Debugger("panic")
>> >
>> > CPU0 stopping CPUs: 0x00000002... stopped.
>> > Stopped at Debugger+0x45: pushl %ebx
>> > db> t
>> > Debugger(c02e3759) at Debugger+0x45
>> > panic(c02e2d60,c02fb929,c7ba8a60,c7ba7b80,fffea000) at panic+0xd0
>> > _mtx_lock_spin(c0357400,0,80246,c02e3a48,2fb) at _mtx_lock_spin+0x6e
>> > wakeup(c3709378,c3709378,c0eec000,c0f71400,c3709454) at wakeup+0x67
>> > bufdone(c3709378,c7fbff40,c0131efb,c3709378,c0f71400) at bufdone+0x385
>> > bufdonebio(c3709378) at bufdonebio+0xe
>> > dadone(c0f5d100,c0f71400) at dadone+0x1f7
>> > camisr(c032a834) at camisr+0x231
>> > ithread_loop(c0b2f080,c7fbffa8) at ithread_loop+0x247
>> > fork_exit(c019898c,c0b2f080,c7fbffa8) at fork_exit+0x83
>> > fork_trampoline() at fork_trampoline+0x8
>>
>> Did you get a crashdump (probably not.) If you look at sched_lock, one of
>> the
>> words will be a pointer to the process owning the lock in question.
>> Unfortunately it's not the first word anymore (something I may change in the
>> future). On the alpha it would be 'sched_lock+48'. The pointer there
>> points
>> to the process owning the lock (and you can look up the process via ps). If
>> you have a crash dump then I have some gdb macros that make it easy to get a
>> backtrace of that process. If not, then, well, it gets harder. :-P Hmm, it
>> might be nice to be able to ask ddb to give a backtrace of any arbitrary
>> process. Maybe I'll add a new command for that..
>>
>> The trick is that we want to know who grabbed sched_lock where and then
>> started
>> spinning with it. Using KTR with KTR_LOCK turned on and using the 'show
>> ktr'
>> command in ddb could also be used to see which process was the last to grab
>> sched_lock and where it was grabbed.
>
> If it happens again, I''ll try. This was, btw, i386.
Oh, duh. Umm, on i386 it's 'sched_lock + 28'.
--
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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