Messages in this thread | | | Date | Wed, 15 Feb 2006 15:17:16 -0800 | From | Andrew Morton <> | Subject | Re: SMP BUG |
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Russell King <rmk+lkml@arm.linux.org.uk> wrote: > > On Mon, Feb 13, 2006 at 07:19:19PM -0500, Hubertus Franke wrote: > > Folks the change introduced in 2.6.16-rc2 over 2.6.15 > > wrt to the SMP initialization are wrong. > > Please apply to unroll the change.. > > > > Here is the logic ... > > sched_init is called from start_kernel before the > > architecture specific function cpu_check_smp() is called > > which is done as part of rest_init(). > > > > On s390 this actually sets the cpu_possible_map, which > > is now used in sched_init through the for_each_cpu without > > properly being initialized. > > As a result bringing 2nd and subsequent cpu online > > breaks. > > > > This should be a quick fix, until this chicken and egg > > problem is solved otherwise. > > > > -- Hubertus > > > > --- kernel/sched.c.orig 2006-02-13 19:08:28.000000000 -0500 > > +++ kernel/sched.c 2006-02-13 19:09:08.000000000 -0500 > > @@ -6111,7 +6111,7 @@ void __init sched_init(void) > > runqueue_t *rq; > > int i, j, k; > > > > - for_each_cpu(i) { > > + for (i = 0; i < NR_CPUS; i++ ) { > > prio_array_t *array; > > > > rq = cpu_rq(i); > > (left most of the message intact because it seems to have been ignored. > Copying Linus and akpm in the vague hope of a response.)
This has already been fixed in s390.
> Yes, I'm also seeing an oops caused by exactly this on ARM: > > ... > > enqueue_task is being called with p = c03fe2e0, array = NULL, leading > to a NULL pointer dereference because rq->array has not been initialised.
Is arm's setup_arch() populating cpu_possible_map?
If that's not possible, statically initialising it to CPU_MASK_ALL should fix it, but that's a lame solution and might lead to wastage of per-cpu memory on not-possible CPUs.
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