lkml.org 
[lkml]   [2009]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] v2 Teach RCU that idle task is not quiscent state at boot
On Mon, Feb 23, 2009 at 09:08:54PM -0800, Paul E. McKenney wrote:
> On Tue, Feb 24, 2009 at 03:02:56PM +1100, Nick Piggin wrote:
> > On Tuesday 24 February 2009 07:43:32 Paul E. McKenney wrote:
> >
> > > @@ -80,6 +81,10 @@ void wakeme_after_rcu(struct rcu_head *head)
> > > void synchronize_rcu(void)
> > > {
> > > struct rcu_synchronize rcu;
> > > +
> > > + if (num_online_cpus() == 1)
> > > + return; /* If UP, synchronize_rcu() is a grace period! */
> > > +
> >
> > Nice patch... May I just suggest a comment to say that this is
> > also a correctness requirement due to the grace period holdoff
> > for early boot?
>
> Excellent point! If Ingo reports that this actually fixes the hang that
> he saw, I will add such a comment.
>
> (And glad you like the patch!)

Gah!!! I forgot about preemptable RCU, which the previous patch breaks
completely on single-CPU systems.

A fix is in the works.

Thanx, Paul


\
 
 \ /
  Last update: 2009-02-24 15:53    [W:0.045 / U:0.284 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site