lkml.org 
[lkml]   [2008]   [Dec]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] tracing/function-graph-tracer: prevent from hrtimer interrupt infinite loop

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> Impact: fix a system hang on slow systems
>
> While testing the function graph tracer on VirtualBox, I had a system hang
> immediatly after enabling the tracer.
>
> If hrtimer is enabled on kernel, a slow system can spend too much time
> during tracing the hrtimer_interrupt which will do eternal loops,
> assuming it always have to retry its process because too much time
> elapsed during its time update. Now we provide a feature which lurks at
> the number of retries on hrtimer_interrupt. After 10 retries, the
> function graph tracer will definetly stop its tracing.

hm, i dont really like this solution - it just works around the problem by
'speeding up' the system. If we have a _real_ slow system, there's no such
way for us to speed it up.

Thomas, what do you think - would you expect this lockup to happen on
really slow systems? If yes, is there a way we could avoid it from
happening - by driving some sort of 'mandatory interval', that is doubled
in size every time we detect such a bad hrtimer loop?

Ingo


\
 
 \ /
  Last update: 2008-12-18 11:37    [W:0.256 / U:0.500 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site