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>
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index 086816b..6ab2440 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -163,19 +163,22 @@
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)) {