lkml.org 
[lkml]   [2012]   [Sep]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU CPU stall warnings
From
Date
On Thu, 2012-09-06 at 11:07 -0400, Steven Rostedt wrote:
> On Thu, 2012-09-06 at 16:56 +0200, Peter Zijlstra wrote:
> > On Thu, 2012-08-30 at 11:56 -0700, Paul E. McKenney wrote:
> > >
> > > If a given CPU avoids the idle loop but also avoids starting a new
> > > RCU grace period for a full minute, RCU can issue spurious RCU CPU
> > > stall warnings. This commit fixes this issue by adding a check for
> > > ongoing grace period to avoid these spurious stall warnings.
> >
> > How would it avoid starting a new period for over a minute? fqs should
> > happen, right? And holding rcu_read_lock() for over a minute surely is a
> > bug.
>
> I can see this happening in test cases, but it would seem weird on a
> normal system. That is, for preempt rcu, having a process scheduled out
> holding an rcu_read_lock() for over a minute could happen on a really
> stressed out system. But for such a case, I don't think a warning is out
> of question.

One would hope that fqs would boost things.. but yeah, if your app is
spinning above the rcu boost prio you're still toast. But in that case
you're right, a warning is fully deserved.


\
 
 \ /
  Last update: 2012-09-07 10:01    [W:2.163 / U:0.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site