Re: 3.12.9-rt13: BUG: soft lockup

From: Fernando Lopez-Lezcano
Date: Fri Feb 14 2014 - 13:55:24 EST


On 02/14/2014 02:43 AM, Thomas Gleixner wrote:
On Thu, 13 Feb 2014, Fernando Lopez-Lezcano wrote:
On 02/13/2014 03:55 PM, Thomas Gleixner wrote:
On Thu, 13 Feb 2014, Fernando Lopez-Lezcano wrote:

On 02/13/2014 02:25 PM, Thomas Gleixner wrote:
On Wed, 12 Feb 2014, Fernando Lopez-Lezcano wrote:
[771508.546449] RIP: 0010:[<ffffffff810dc60a>] [<ffffffff810dc60a>]
smp_call_function_many+0x2ca/0x330

Can you decode the exact location inside of smp_call_function_many via
addr2line please ?

# addr2line -e
/usr/lib/debug/lib/modules/3.12.9-301.rt13.1.fc20.ccrma.x86_64+rt/vmlinux
ffffffff810dc60e
/usr/src/debug/kernel-3.12.fc20.ccrma/linux-3.12.9-301.rt13.1.fc20.ccrma.x86_64/kernel/smp.c:108

So it's stuck in csd_lock_wait(), which means that the csd of the
target cpu is not free.

Is the machine completely dead or can you still retrieve information
from it?

After migrating to fc20/3.12.x-rtyy I started experiencing freezes in some workstations. This coincided with one of our students running high cpu load multi-core computations in them (he had been doing that before under 3.10.x-rtyy with no problems). In the morning I would find workstations unresponsive and catatonic. Probably his software was still eating up cpu as the machines were warm (ie: still under load). No pings back or keyboard/mouse/display response.

This was the only time I could get information from a machine while it was in the process of freezing up - but this might have been a different issue. I was ssh'd in and that terminal became unresponsive. I managed to ssh in again and looked at the logs. The machine was not completely frozen but it eventually became completely catatonic. For all I know this might be different from the locked machines syndrome as it left traces in the logs (I could forward you all the log entries if you want).

I could try to boot one of the machines into 3.12.xrtyy, replicate the conditions and wait. What should I look for if I can catch this in the act?

-- Fernando
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