[PATCH] Fixed division by zero bug in kernel/padata.c
in [Kernel]
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From: Dan Kruchinin on 2 Jul 2010 08:10 When boot CPU(typically CPU #0) is excluded from padata cpumask and user enters halt command from console, kernel faults on division by zero; This occurs because during the halt kernel shuts down each non-boot CPU one by one and after it shuts down the last CPU that is set in the padata cpumask, the only working CPU in the system is a boot CPU(#0) and it's the only CPU that is set in the cpu_active_mask. Hence when padata_cpu_callback calls __padata_remove_cpu(which calls padata_alloc_pd) it appears that padata cpumask and cpu_active_mask aren't intersect. Hence the following code in padata_alloc_pd causes a DZ error exception: cpumask_and(pd->cpumask, cpumask, cpu_active_mask); // pd->cpumask will be empty ... num_cpus = cpumask_weight(pd->cpumask); // num_cpus = 0 pd->max_seq_nr = (MAX_SEQ_NR / num_cpus) * num_cpus - 1; // DZ! Signed-off-by: Dan Kruchinin <dkruchinin(a)acm.org> --- kernel/padata.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/padata.c b/kernel/padata.c index fdd8ae6..dbe6d26 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -434,7 +434,7 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst, atomic_set(&queue->num_obj, 0); } - num_cpus = cpumask_weight(pd->cpumask); + num_cpus = cpumask_weight(pd->cpumask) + 1; pd->max_seq_nr = (MAX_SEQ_NR / num_cpus) * num_cpus - 1; setup_timer(&pd->timer, padata_reorder_timer, (unsigned long)pd); -- 1.7.1 -- W.B.R. Dan Kruchinin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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