linux-kernel - Re: frequent softlockups with 3.10rc6.

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Date:	Mon, 24 Jun 2013 16:39:28 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Dave Jones <davej@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrey Vagin <avagin@...nvz.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: frequent softlockups with 3.10rc6.

On 06/23, Dave Jones wrote:
>
> On Sun, Jun 23, 2013 at 06:04:52PM +0200, Oleg Nesterov wrote:
>
>  > Could you please do the following:
>  >
>  > 	1. # cd /sys/kernel/debug/tracing
>  > 	   # echo 0 >> options/function-trace
>  > 	   # echo preemptirqsoff >> current_tracer
>
> dammit.
>
> WARNING: at include/linux/list.h:385 rb_head_page_deactivate.isra.39+0x61/0x80()

Hmmm. which kernel do use use?

   380  #define list_for_each(pos, head) \
   381          for (pos = (head)->next; pos != (head); pos = pos->next)
   382
   383  /**
   384   * __list_for_each      -       iterate over a list
   385   * @pos:        the &struct list_head to use as a loop cursor.
   386   * @head:       the head for your list.
   387   *
   388   * This variant doesn't differ from list_for_each() any more.
   389   * We don't do prefetching in either case.
   390   */
   391  #define __list_for_each(pos, head) \
   392          for (pos = (head)->next; pos != (head); pos = pos->next)
   393
   394  /**
   395   * list_for_each_prev   -       iterate over a list backwards
   396   * @pos:        the &struct list_head to use as a loop cursor.
   397   * @head:       the head for your list.
   398   */
   399  #define list_for_each_prev(pos, head) \
   400          for (pos = (head)->prev; pos != (head); pos = pos->prev)

On 9e895ace5d8 (Linux 3.10-rc7).

>  check_list_nodes corruption. next->prev should be prev (ffff88023b8a1a08), but was 00ffff88023b8a1a. (next=ffff880243288001).

Can't find "check_list_nodes" in lib/list_debug.c or elsewhere...

>   [<ffffffff816e467d>] dump_stack+0x19/0x1b
>   [<ffffffff8104a0c1>] warn_slowpath_common+0x61/0x80
>   [<ffffffff8104a12c>] warn_slowpath_fmt+0x4c/0x50
>   [<ffffffff81112c61>] rb_head_page_deactivate.isra.39+0x61/0x80

How? rb_list_head_clear() just modifies list->next directly.

> hopefully despite that it'll actually function as intended.

Yes ;)

Oleg.

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