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[POWERPC] Fix possible access to free pages 

I think we have a subtle race on ppc64 with the tlb batching.  The
common code expects tlb_flush() to actually flush any pending TLB
batch.  It does that because it delays all page freeing until after
tlb_flush() is called, in order to ensure no stale reference to
those pages exist in any TLB, thus causing potential access to
the freed pages.

However, our tlb_flush only triggers the RCU for freeing page
table pages, it does not currently trigger a flush of a pending
TLB/hash batch, which is, I think, an error.  This fixes it.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Benjamin Herrenschmidt 2007-05-27 15:18:22 +10:00 committed by Paul Mackerras
parent 988519acb3
commit 6ad8d010b2
1 changed files with 9 additions and 0 deletions
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9
include/asm-powerpc/tlb.h
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@ -38,6 +38,15 @@ extern void pte_free_finish(void);
static inline void tlb_flush(struct mmu_gather *tlb)
{
struct ppc64_tlb_batch *tlbbatch = &__get_cpu_var(ppc64_tlb_batch);
/* If there's a TLB batch pending, then we must flush it because the
* pages are going to be freed and we really don't want to have a CPU
* access a freed page because it has a stale TLB
*/
if (tlbbatch->index)
__flush_tlb_pending(tlbbatch);
pte_free_finish();
}