[PATCH] mm: tlb_gather_mmu get_cpu_var

tlb_gather_mmu dates from before kernel preemption was allowed, and uses
smp_processor_id or __get_cpu_var to find its per-cpu mmu_gather.  That works
because it's currently only called after getting page_table_lock, which is not
dropped until after the matching tlb_finish_mmu.  But don't rely on that, it
will soon change: now disable preemption internally by proper get_cpu_var in
tlb_gather_mmu, put_cpu_var in tlb_finish_mmu.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/asm-ia64/tlb.h b/include/asm-ia64/tlb.h
index 3a9a6d1be75c..1b82299d7c1e 100644
--- a/include/asm-ia64/tlb.h
+++ b/include/asm-ia64/tlb.h
@@ -129,7 +129,7 @@ ia64_tlb_flush_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long e
 static inline struct mmu_gather *
 tlb_gather_mmu (struct mm_struct *mm, unsigned int full_mm_flush)
 {
-        struct mmu_gather *tlb = &__get_cpu_var(mmu_gathers);
+        struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
 
         tlb->mm = mm;
         /*
@@ -154,7 +154,7 @@ tlb_gather_mmu (struct mm_struct *mm, unsigned int full_mm_flush)
 
 /*
  * Called at the end of the shootdown operation to free up any resources that were
- * collected.  The page table lock is still held at this point.
+ * collected.
  */
 static inline void
 tlb_finish_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long end)
@@ -174,6 +174,8 @@ tlb_finish_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long end)
 
         /* keep the page table cache within bounds */
         check_pgt_cache();
+
+        put_cpu_var(mmu_gathers);
 }
 
 static inline unsigned int