powerpc/mm: Make hpte_need_flush() safe for preemption

hpte_need_flush() might be called outside of a preempt section
when manipulating the kernel page tables, so we need to use the
appopriate variants of per-cpu variable accesses. There should
be no risk of being in the middle of a batch and a context
switch will flush any pending batch.

[Patch extracted from a larger patch in Peter's preemptible
 mmu_gather series]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/mm/tlb_hash64.c b/arch/powerpc/mm/tlb_hash64.c
index 1ec0657..c14d09f 100644 (file)
--- a/arch/powerpc/mm/tlb_hash64.c
+++ b/arch/powerpc/mm/tlb_hash64.c
@@ -38,13 +38,11 @@ DEFINE_PER_CPU(struct ppc64_tlb_batch, ppc64_tlb_batch);
  * neesd to be flushed. This function will either perform the flush
  * immediately or will batch it up if the current CPU has an active
  * batch on it.
- *
- * Must be called from within some kind of spinlock/non-preempt region...
  */
 void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
                     pte_t *ptep, unsigned long pte, int huge)
 {
-       struct ppc64_tlb_batch *batch = &__get_cpu_var(ppc64_tlb_batch);
+       struct ppc64_tlb_batch *batch = &get_cpu_var(ppc64_tlb_batch);
        unsigned long vsid, vaddr;
        unsigned int psize;
        int ssize;
@@ -99,6 +97,7 @@ void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
         */
        if (!batch->active) {
                flush_hash_page(vaddr, rpte, psize, ssize, 0);
+               put_cpu_var(ppc64_tlb_batch);
                return;
        }
 
@@ -127,6 +126,7 @@ void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
        batch->index = ++i;
        if (i >= PPC64_TLB_BATCH_NR)
                __flush_tlb_pending(batch);
+       put_cpu_var(ppc64_tlb_batch);
 }
 
 /*