lkml.org 
[lkml]   [2017]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH 2/2] lib: debugobjects: touch watchdog to avoid softlockup when !CONFIG_PREEMPT
From
Date
On 11/27/2017 12:54 PM, Yang Shi wrote:
> Hi Waiman,
>
> The second patch of this series.
>
> Thanks,
> Yang
>
>
> On 11/17/17 11:43 AM, Yang Shi wrote:
>> There are nested loops on debug objects free path, sometimes it may take
>> over hundred thousands of loops, then cause soft lockup with
>> !CONFIG_PREEMPT
>> occasionally, like below:
>>
>> ...
>>
>> The code path might be called in either atomic or non-atomic context,
>> so touching softlockup watchdog instead of calling cond_resched() which
>> might fall asleep. However, it is unnecessary to touch the watchdog
>> every loop, so just touch the watchdog at every 10000 (best estimate)
>> loops.
>>
>> Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>

I do have some concern about suppressing the soft lockup warning
entirely. If the system feels unresponsive for a certain period of time
(e.g. 22s), most users would like to know what is going on. It can be a
custom message with less scary warning. Alternatively, some opt-out
mechanism can be added to explicitly disable soft lookup warning for
debugobjs is OK as long as it is not the default.

Cheers,
Longman

\
 
 \ /
  Last update: 2017-11-27 19:19    [W:0.051 / U:11.248 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site