Re: [PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU CPU stallwarnings

[Steven Rostedt]

On Fri, 2012-09-07 at 09:00 +0200, Peter Zijlstra wrote:
> On Thu, 2012-09-06 at 15:22 -0700, Paul E. McKenney wrote:
> > Ah!
> > 
> > It is perfectly legal to avoid -starting- an RCU grace period for a
> > minute, or even longer.  If RCU has nothing to do, in other words, if no
> > one registers any RCU callbacks, then RCU need not start a grace period.
> > 
> > Of course, this would mean that it would eventually be a full minute
> > since the last start of a grace period.  This is not a problem, after
> > all, Linux went through a full ten years before experiencing its first
> > grace period.
> > 
> > But the stall-warning code just checked how long it had been since
> > the last start of a grace period, failing to note that this grace
> > period had long since completed.  So it splatted out a warning.
> > This warning was spurious in the sense that there was no bug aside
> > from the missing check that the grace period was still in progress.
> > 
> > And this commit fixes that bug in RCU. 
> 
> OK, that makes sense.. it just looks like both Steve and me got confused
> by the initial changelog. 

Right, I think the change log needs to be fixed ;-)

-- Steve


--
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/