[lkml]   [2012]   [Sep]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: rcu self-detected stall messages on OMAP3, 4 boards
Hi Paul

On Sat, 22 Sep 2012, Paul E. McKenney wrote:

> Strangely enough, I believe that I have inadvertently fixed this in
> my -rcu tree:
> git:// rcu/next
> Nevertheless, if you get a chance to try it, I would be interested to
> hear if my guess is correct.

Yes, good news: the stall warnings go away with that branch.

> The trick is that a kthread drives the grace period in -rcu, regardless
> of whether or not there are callbacks.

This is "rcu: Move quiescent-state forcing into kthread" ?

Added some debugging into rcu_gp_kthread() after that commit and can
confirm that the quiescent-state forcing loop does start a few times when
there are zero callbacks pending (modulo any races in my measurement

> However, the backport would not be something that -stable would be happy
> with, so I will be putting together a fix for mainline. This thing
> has been in the kernel since about 2004, not sure why you didn't hit
> it earlier.

One other data point in that regard - noticed the warnings don't appear
when the board is booted with:

commit 4fa3b6cb1bc8c14b81b4c8ffdfd3f2500a7e9367
Author: Paul E. McKenney <>
Date: Tue Jun 5 15:53:53 2012 -0700

rcu: Fix qlen_lazy breakage


- Paul

 \ /
  Last update: 2012-09-23 00:41    [W:0.049 / U:8.668 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site