lkml.org 
[lkml]   [2009]   [Jan]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch] Re: [Bug #12100] resume (S2R) broken by Intel microcode module, on A110L
Dmitry Adamushko wrote:
> 2009/1/11 Ingo Molnar <mingo@elte.hu>:
>> * Ingo Molnar <mingo@elte.hu> wrote:
>>
>>> * Dmitry Adamushko <dmitry.adamushko@gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>>
>>>> This is in response to the following bug report:
>>>>
>>>> Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12100
>>>> Subject : resume (S2R) broken by Intel microcode module, on A110L
>>>> Submitter : Andreas Mohr <andi@lisas.de>
>>>> Date : 2008-11-25 08:48 (19 days old)
>>>> Handled-By : Dmitry Adamushko <dmitry.adamushko@gmail.com>
>>> applied to tip/x86/microcode, thanks Dmitry!
>>>
>>> The fix looks right but somewhat intrusive in scope, so i'm a bit
>>> reluctant to push it towards .28 straight away - without having feedback
>>> in the bugzilla. If feedback is positive (the bug reported there goes
>>> away completely) we can cherry-pick it over into x86/urgent, ok? And in
>>> any case i've marked it as a -stable backport for .28.1.
>> hm, -tip testing just found this microcode locking lockdep splat:
>>
>> [ 48.004158] SMP alternatives: switching to UP code
>> [ 48.342853] CPU0 attaching NULL sched-domain.
>> [ 48.344288] CPU1 attaching NULL sched-domain.
>> [ 48.354696] CPU0 attaching NULL sched-domain.
>> [ 48.361215] device: 'cpu1': device_unregister
>> [ 48.364231] device: 'cpu1': device_create_release
>> [ 48.368138]
>> [ 48.368139] =======================================================
>> [ 48.372039] [ INFO: possible circular locking dependency detected ]
>> [ 48.372039] 2.6.29-rc1-tip-00901-g9699183-dirty #15577
>> [ 48.372039] -------------------------------------------------------
>> [ 48.372039] S99local/3496 is trying to acquire lock:
>> [ 48.372039] (microcode_mutex){--..}, at: [<c0118489>] microcode_fini_cpu+0x17/0x2b
>> [ 48.372039]
>> [ 48.372039] but task is already holding lock:
>> [ 48.372039] (&cpu_hotplug.lock){--..}, at: [<c012f508>] cpu_hotplug_begin+0x1f/0x47
>> [ 48.372039]
>> [ 48.372039] which lock already depends on the new lock.
>> [ 48.372039]
>> [ 48.372039]
>> [ 48.372039] the existing dependency chain (in reverse order) is:
>> [ 48.372039]
>> [ 48.372039] -> #1 (&cpu_hotplug.lock){--..}:
>> [ 48.372039] [<c014d3f1>] validate_chain+0x8e9/0xb94
>> [ 48.372039] [<c014dd03>] __lock_acquire+0x667/0x6e1
>> [ 48.372039] [<c014ddda>] lock_acquire+0x5d/0x7a
>> [ 48.372039] [<c0a6fac3>] mutex_lock_nested+0xdc/0x170
>> [ 48.372039] [<c012f552>] get_online_cpus+0x22/0x34
>> [ 48.372039] [<c013ce08>] work_on_cpu+0x50/0x8a
>> [ 48.372039] [<c0118465>] microcode_init_cpu+0x25/0x32
>> [ 48.372039] [<c0118699>] mc_sysdev_add+0x91/0x9b
>> [ 48.372039] [<c04cbd09>] sysdev_driver_register+0x9b/0xea
>
> I'll check more carefully... At the first glance, the presence of
> work_on_cpu() looks strange.
>
> My first idea was that it's used somewhere by request_firmware() but
> even assuming some functions might have been inlined (and a call via a
> function pointer is not shown either), I don't immediately see how we
> might end up with microcode_init_cpu() -> ... -> work_on_cpu().

It was in a commit that (it appears) Ingo has reverted:

Subject: x86: cleanup remaining cpumask_t code in microcode_core.c

Impact: Reduce problem with changing current->cpus_allowed mask directly.

Use "work_on_cpu" to replace instances where set_cpus_allowed_ptr was being used.

Signed-off-by: Mike Travis <travis@sgi.com>


This work_on_cpu is to replace setting current->cpus_allowed when it's
only for one cpu. But it has a call to get_online_cpus() that (I believe)
is just to keep from offlining the cpu the work function is running on.
And it's also the cause of the circular lock dependencies.

Thanks,
Mike


>
> I've locked up all the use cases of work_on_cpu() in the current -tip
> (about 20), and none of them seem to explain its appearance in the
> trace. weird...
>
>
>> Ingo
>>
>



\
 
 \ /
  Last update: 2009-01-11 21:15    [W:0.675 / U:0.504 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site