From: David Ahern <dsahern@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Eric Dumazet <eric.dumazet@gmail.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [BUG] kernel freezes with latest tree
Date: Tue, 10 Jan 2012 23:35:07 -0700 [thread overview]
Message-ID: <4F0D2D9B.8030501@gmail.com> (raw)
In-Reply-To: <CA+55aFwYmX7q4MZc-xOStZB2ZQjVt_Jca6qDP+0cPKekz8yL+A@mail.gmail.com>
On 01/10/2012 04:44 PM, Linus Torvalds wrote:
> Anybody? Any ideas? Clearly there can be a merge problem that doesn't
> actually show as a real data conflict, just some semantic conflict,
> but I don't see what such issues would be brouht in by the scheduler
> merge anyway.
This is really easy to reproduce in a KVM hosted VM.
Using the gdb stub one cpu is spinning here:
(gdb) bt
#0 try_to_wake_up (p=0xf529b200, state=<optimized out>, wake_flags=1)
at /mnt/sw/kernel-2.6.git/kernel/sched/core.c:1575
#1 0xc0470ab0 in default_wake_function (curr=<optimized out>,
mode=<optimized out>,
wake_flags=<optimized out>, key=0xc3) at
/mnt/sw/kernel-2.6.git/kernel/sched/core.c:3364
So basically:
while (p->on_cpu) {
...
cpu_relax();
}
And the other vcpu is here:
#0 tg_load_down (tg=0xf55b9c00, data=<optimized out>) at
/mnt/sw/kernel-2.6.git/kernel/sched/fair.c:3351
#1 0xc0470049 in walk_tg_tree_from (from=0xc0ba5400, down=0xc04753c0
<tg_load_down>, up=0xc046a3b0 <tg_nop>,
data=0x0) at /mnt/sw/kernel-2.6.git/kernel/sched/core.c:664
#2 0xc04793f7 in walk_tg_tree (data=<optimized out>, up=<optimized
out>, down=0xc04753c0 <tg_load_down>)
at /mnt/sw/kernel-2.6.git/kernel/sched/sched.h:175
#3 update_h_load (cpu=<optimized out>) at
/mnt/sw/kernel-2.6.git/kernel/sched/fair.c:3361
#4 load_balance_fair (lb_flags=<synthetic pointer>,
idle=CPU_NEWLY_IDLE, sd=0xf5c30800, max_load_move=278,
busiest=0xf6607d00, this_cpu=1, this_rq=0xf6707d00) at
/mnt/sw/kernel-2.6.git/kernel/sched/fair.c:3374
#5 move_tasks (lb_flags=<synthetic pointer>, idle=CPU_NEWLY_IDLE,
sd=0xf5c30800, max_load_move=278,
busiest=<optimized out>, this_cpu=1, this_rq=0xf6707d00)
at /mnt/sw/kernel-2.6.git/kernel/sched/fair.c:3444
#6 load_balance (this_cpu=1, this_rq=0xf6707d00, sd=0xf5c30800,
idle=CPU_NEWLY_IDLE, balance=0xf5217cb4)
at /mnt/sw/kernel-2.6.git/kernel/sched/fair.c:4496
#7 0xc0479be2 in idle_balance (this_cpu=1, this_rq=0xf6707d00)
at /mnt/sw/kernel-2.6.git/kernel/sched/fair.c:4640
Based on the file in question (sched/fair.c) I took a stab at guessing
the commit: without a195f004 I was not able to lock it up. With the
patch the VM spins after a few hackbench iterations.
I don't have time for a proper bisect tonight. I can do that in the a.m.
if I am not totally off base here. Peter: any chance this commit could
explain the spinning cpus / system freeze?
David
next prev parent reply other threads:[~2012-01-11 6:35 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-10 4:57 [BUG] kernel freezes with latest tree Eric Dumazet
2012-01-10 5:03 ` Eric Dumazet
2012-01-10 8:16 ` Eric Dumazet
2012-01-10 16:13 ` Eric Dumazet
2012-01-10 16:28 ` Linus Torvalds
2012-01-10 16:37 ` Eric Dumazet
2012-01-10 16:49 ` Linus Torvalds
2012-01-10 16:53 ` Eric Dumazet
2012-01-10 17:00 ` Linus Torvalds
2012-01-10 19:32 ` Ingo Molnar
2012-01-10 22:23 ` Eric Dumazet
2012-01-10 23:44 ` Linus Torvalds
2012-01-11 6:35 ` David Ahern [this message]
2012-01-11 9:04 ` Peter Zijlstra
2012-01-11 10:28 ` Eric Dumazet
2012-01-11 11:29 ` Eric Dumazet
2012-01-11 12:25 ` Peter Zijlstra
2012-01-11 13:24 ` Eric Dumazet
2012-01-11 15:56 ` Ingo Molnar
2012-01-11 16:05 ` Peter Zijlstra
2012-01-11 16:14 ` Ingo Molnar
2012-01-11 16:31 ` Linus Torvalds
2012-01-11 16:58 ` Peter Zijlstra
2012-01-12 6:17 ` [tip:sched/urgent] sched: Fix lockup by limiting load-balance retries on lock-break tip-bot for Peter Zijlstra
2012-01-11 8:22 ` [BUG] kernel freezes with latest tree Eric Dumazet
2012-01-11 14:20 ` Frederic Weisbecker
2012-01-10 16:16 ` Linus Torvalds
2012-01-10 16:33 ` Eric Dumazet
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