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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>
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1 changed files with 8 additions and 5 deletions
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@ -163,19 +163,22 @@ static DEFINE_PER_CPU(int, kmap_high_l1_vipt_depth);
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void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte)
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{
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unsigned int idx, cpu = smp_processor_id();
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int *depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
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unsigned int idx, cpu;
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int *depth;
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unsigned long vaddr, flags;
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pte_t pte, *ptep;
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if (!in_interrupt())
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preempt_disable();
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cpu = smp_processor_id();
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depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
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idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
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vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
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ptep = TOP_PTE(vaddr);
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pte = mk_pte(page, kmap_prot);
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if (!in_interrupt())
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preempt_disable();
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raw_local_irq_save(flags);
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(*depth)++;
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if (pte_val(*ptep) == pte_val(pte)) {
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