Re: rcu_dyntick and suspicious RCU usage
From: Paul E. McKenney
Date: Tue Jul 17 2012 - 16:59:04 EST
On Fri, Jul 13, 2012 at 05:12:30PM +0800, Fengguang Wu wrote:
> On Thu, Jul 12, 2012 at 10:02:42AM -0700, Paul E. McKenney wrote:
> > On Fri, Jul 13, 2012 at 12:57:38AM +0800, Fengguang Wu wrote:
> > > On Thu, Jul 12, 2012 at 09:43:08AM -0700, Paul E. McKenney wrote:
> > > > On Wed, Jul 11, 2012 at 12:49:24AM -0700, Paul E. McKenney wrote:
> > > > > On Tue, Jul 10, 2012 at 12:47:00PM +0800, Fengguang Wu wrote:
> > > > > > Hi Paul,
> > > > > >
> > > > > > Fortunately this bug is bisectable and the first bad commit is:
> > > > > >
> > > > > > commit 9b2e4f1880b789be1f24f9684f7a54b90310b5c0
> > > > > > Author: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
> > > > > > Date: Fri Sep 30 12:10:22 2011 -0700
> > > > > >
> > > > > > rcu: Track idleness independent of idle tasks
> > > > >
> > > > > OK, there is a problem in TINY_RCU's handling of dyntick-idle: it
> > > > > traces while in idle. The confusion on my part was that in TREE_RCU,
> > > > > the nesting and dyntick-idle indication are different, while in
> > > > > TINY_RCU they are one and the same.
> > > > >
> > > > > Does the following patch help?
> > > >
> > > > This one failed in my testing. Please see the end for the fixed
> > > > version, with on small but important change.
> > >
> > > It worked, thanks!
> > >
> > > Tested-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxx>
> >
> > Very good! (And please ignore my resend of the same patch.)
> >
> > I will queue this.
>
> Will you recommend it for -stable? It impacts 3.3/3.4. I tested it on
> 3.4 and it works fine. However for 3.3, the patch cannot apply cleanly.
If someone hits it in a real workload, I might consider it. I currently
have it queued for 3.7.
Thanx, Paul
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/