linux-kernel - Re: lock-up with module: Optimize __module

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Date:	Tue, 7 Jul 2015 16:33:05 +0000 (UTC)
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Arthur Marsh <arthur.marsh@...ernode.on.net>
Cc:	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	rostedt <rostedt@...dmis.org>, Oleg Nesterov <oleg@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: lock-up with module: Optimize __module_address() using a
 latched RB-tree

----- On Jul 7, 2015, at 3:29 AM, Peter Zijlstra peterz@...radead.org wrote:

> On Tue, Jul 07, 2015 at 02:59:06PM +0930, Arthur Marsh wrote:
>> I had a single, non-reproducible case of the same lock-up happening on my
>> other machine running the Linus git head kernel in 64-bit mode.
> 
> Hmm, disturbing.. I've had my machines run this stuff for weeks and not
> had anything like this :/
> 
> Do you have a serial cable between those machines? serial console output
> will allow capturing more complete traces than these pictures can and
> might also aid in capturing some extra debug info.
> 
> In any case, I'll go try and build some debug code.

Arthur: can you double-check if you load any module with --force ?
This could cause a module header layout mismatch, which can be an
issue with the changes done by the identified commit: the module
header layout changes there.

Also, I'm attaching a small patch which serializes both updates and
reads of the module rbree. Can you try it out ? If the problem
still shows with the spinlocks in place, that would mean the issue
is *not* a race between latched rbtree updates and traversals.

Thanks!

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

View attachment "0001-TESTING-add-spinlock-to-module.c-rb-latch-tree.patch" of type "text/x-patch" (2225 bytes)