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ARM: 6279/1: highmem: fix SMP preemption bug in kmap_high_l1_vipt 

smp_processor_id() must not be called from a preemptible context (this
is checked by CONFIG_DEBUG_PREEMPT).  kmap_high_l1_vipt() was doing so.
This lead to a problem where the wrong per_cpu kmap_high_l1_vipt_depth
could be incremented, causing a BUG_ON(*depth <= 0); in
kunmap_high_l1_vipt().

The solution is to move the call to smp_processor_id() after the call
to preempt_disable().

Originally by: Andrew Howe <ahowe@nvidia.com>

Signed-off-by: Gary King <gking@nvidia.com>
Acked-by: Nicolas Pitre <nico.as.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Gary King 2010-07-29 17:37:20 +01:00 committed by Russell King
parent b92b361213
commit 831e8047eb
1 changed files with 8 additions and 5 deletions
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13
arch/arm/mm/highmem.c
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@ -163,19 +163,22 @@ static DEFINE_PER_CPU(int, kmap_high_l1_vipt_depth);
void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte)
{
unsigned int idx, cpu = smp_processor_id();
int *depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
unsigned int idx, cpu;
int *depth;
unsigned long vaddr, flags;
pte_t pte, *ptep;
if (!in_interrupt())
preempt_disable();
cpu = smp_processor_id();
depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
ptep = TOP_PTE(vaddr);
pte = mk_pte(page, kmap_prot);
if (!in_interrupt())
preempt_disable();
raw_local_irq_save(flags);
(*depth)++;
if (pte_val(*ptep) == pte_val(pte)) {