Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-01

Paul E. McKenney
2005-03-22T05:50:05Z

On Mon, Mar 21, 2005 at 10:06:22AM +0100, Ingo Molnar wrote:
>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> >
> > * Ingo Molnar <mingo@elte.hu> wrote:
> >
> > > got this early-bootup crash on an SMP box:
> >
> > the same kernel image boots fine on an UP box, so it's an SMP bug.
> >
> > note that the same occurs with your latest (synchronization barrier)
> > fixes applied as well.
>
> i've uploaded my current tree (-V0.7.41-01) to:
>
> http://redhat.com/~mingo/realtime-preempt/
>
> it includes the latest round of RCU fixes - but doesnt solve the SMP
> bootup crash.

Hello, Ingo,

Does the following help with the SMP problem? This fix and the earlier
one make my old patch survive a few rounds of kernbench on a 4-CPU x86
box. (Yes, I am still being cowardly! But happy that the test system
is alive again!) Without these fixes, it too dies during boot.

Thanx, Paul

diff -urpN -X dontdiff linux-2.6.11.fixes2/kernel/rcupdate.c linux-2.6.11.fixes3/kernel/rcupdate.c
--- linux-2.6.11.fixes2/kernel/rcupdate.c Mon Mar 21 08:17:00 2005
+++ linux-2.6.11.fixes3/kernel/rcupdate.c Mon Mar 21 20:00:00 2005
@@ -633,7 +633,7 @@ void rcu_check_callbacks(int cpu, int us
{
if ((unsigned long)(jiffies - rcu_ctrlblk.last_sk) >
HZ/GRACE_PERIODS_PER_SEC) {
- synchronize_kernel();
+ _synchronize_kernel();
rcu_advance_callbacks();
rcu_process_callbacks();
}