Re: [stable] [PATCH RFC tip/core/urgent] rcu: Avoid having just-onlined CPU resched itself when RCU is idle

[Greg KH <greg@kroah.com>]

On Fri, Aug 19, 2011 at 09:35:47AM -0700, Paul E. McKenney wrote:
> CPUs set rdp->qs_pending when coming online to resolve races with
> grace-period start.  However, this means that if RCU is idle, the
> just-onlined CPU might needlessly send itself resched IPIs.  Adjust the
> online-CPU initialization to avoid this, and also to correctly cause
> the CPU to respond to the current grace period if needed.
> 
> This patch is believed to fix or otherwise suppress problems in
> https://bugzilla.redhat.com/show_bug.cgi?id=726877, however, the
> relationship is not apparent to this patch's author.  That said, it is
> hard to argue with test results.
> 
> This will be available from -rcu as soon as kernel.org's mirrors update:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git rcu/urgent
> 
> Reported-by: Nicolas Mailhot <nicolas.mailhot@laposte.net>
> Reported-by: Michal Jaegermann <michal@harddata.com>
> Reported-by: Josh Boyer <jwboyer@redhat.com>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Tested-by: Josh Boyer <jwboyer@redhat.com>
> 
>  rcutree.c |   11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
for how to do this properly.

</formletter>