Re: cond_resched() and RCU CPU stall warnings

From: Peter Zijlstra
Date: Tue Mar 18 2014 - 04:52:05 EST


On Mon, Mar 17, 2014 at 07:17:06PM -0700, Paul E. McKenney wrote:
> On Mon, Mar 17, 2014 at 06:14:34PM +0100, Peter Zijlstra wrote:
> > On Mon, Mar 17, 2014 at 09:58:07AM -0700, Paul E. McKenney wrote:
> > > @@ -4111,6 +4115,7 @@ int __sched __cond_resched_softirq(void)
> > > {
> > > BUG_ON(!in_softirq());
> > >
> > > + rcu_cond_resched();
> >
> > Don't you have to enable BHs before doing that? And if not; that needs a
> > comment for sure! :-)
>
> No need to enable BHs, just RCU marking quiescent states. But yes,
> the name does look a bit scary in that context, doesn't it? Added
> a comment, please see below for updated patch.

The below seemed like an unrelated patch entirely :-)

> ------------------------------------------------------------------------
>
> torture: Better summary diagnostics for build failures
>
> The reaction of kvm-recheck.sh is obscure at best, and easy to miss
> completely. This commit therefore prints "BUG: Build failed" in the
> summary at the end of a run.
>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
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