path: root/mm/pgtable-generic.c
diff options
authorRik van Riel <>2012-11-06 09:56:01 +0000
committerMel Gorman <>2012-12-11 14:28:33 +0000
commitcef23d9db6b76732d9b0933cb162358a6a1f43d7 (patch)
tree8f7c96c026156cd92847be022d9031fc96f25df2 /mm/pgtable-generic.c
parente4a1cc56e4d728eb87072c71c07581524e5160b1 (diff)
mm,generic: only flush the local TLB in ptep_set_access_flags
The function ptep_set_access_flags is only ever used to upgrade access permissions to a page. That means the only negative side effect of not flushing remote TLBs is that other CPUs may incur spurious page faults, if they happen to access the same address, and still have a PTE with the old permissions cached in their TLB. Having another CPU maybe incur a spurious page fault is faster than always incurring the cost of a remote TLB flush, so replace the remote TLB flush with a purely local one. This should be safe on every architecture that correctly implements flush_tlb_fix_spurious_fault() to actually invalidate the local TLB entry that caused a page fault, as well as on architectures where the hardware invalidates TLB entries that cause page faults. In the unlikely event that you are hitting what appears to be an infinite loop of page faults, and 'git bisect' took you to this changeset, your architecture needs to implement flush_tlb_fix_spurious_fault to actually flush the TLB entry. Signed-off-by: Rik van Riel <> Cc: Linus Torvalds <> Cc: Andrew Morton <> Cc: Peter Zijlstra <> Cc: Michel Lespinasse <> Cc: Ingo Molnar <>
Diffstat (limited to 'mm/pgtable-generic.c')
1 files changed, 3 insertions, 3 deletions
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index e642627da6b7..d8397da42fe6 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -12,8 +12,8 @@
- * Only sets the access flags (dirty, accessed, and
- * writable). Furthermore, we know it always gets set to a "more
+ * Only sets the access flags (dirty, accessed), as well as write
+ * permission. Furthermore, we know it always gets set to a "more
* permissive" setting, which allows most architectures to optimize
* this. We return whether the PTE actually changed, which in turn
* instructs the caller to do things like update__mmu_cache. This
@@ -27,7 +27,7 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
int changed = !pte_same(*ptep, entry);
if (changed) {
set_pte_at(vma->vm_mm, address, ptep, entry);
- flush_tlb_page(vma, address);
+ flush_tlb_fix_spurious_fault(vma, address);
return changed;