Commit 831e8047 authored Jul 29, 2010 by Gary King Committed by Russell King Jul 30, 2010

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>

parent b92b3612

arch/arm/mm/highmem.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -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)) {

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