Re: CPU hotplug broken in 2.6.8-rc2 ?

[Nathan Lynch <nathanl@austin.ibm.com>]

On Mon, 2004-08-02 at 04:57, Dipankar Sarma wrote:
> Copied to the right email ids to avoid bouncing emails on replies.
> 
> Thanks
> Dipankar
> 
> On Mon, Aug 02, 2004 at 03:19:07PM +0530, Dipankar Sarma wrote:
> > Could it be that recent sched domain stuff broke CPU hotplug ?
> > While testing cpu hotplug with some RCU changes, I got the following
> > panic (while onlining).

Could you try on 2.6.8-rc2-mm2 along with this patch?  Vatsa had a patch
go in that should prevent the crash you are seeing -- the patch below is
needed to prevent the same crash in the offline case.  This check used
to be in load_balance and some other scheduler functions, iirc; does
anyone know why they were removed?

Nathan


---


diff -puN kernel/sched.c~check-for-cpu-offline-in-load_balance kernel/sched.c
--- 2.6.8-rc2-mm2/kernel/sched.c~check-for-cpu-offline-in-load_balance	2004-08-02 13:12:04.000000000 -0500
+++ 2.6.8-rc2-mm2-nathanl/kernel/sched.c	2004-08-02 13:12:58.000000000 -0500
@@ -1405,6 +1405,9 @@ static int load_balance(int this_cpu, ru
 
 	spin_lock(&this_rq->lock);
 
+	if (unlikely(cpu_is_offline(this_cpu)))
+		goto out_balanced;
+
 	group = find_busiest_group(sd, this_cpu, &imbalance, idle);
 	if (!group)
 		goto out_balanced;

_