[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, 3 insertions, 2 deletions

diff --git a/include/asm-arm/tlb.h b/include/asm-arm/tlb.h
index 9bb325c54645..da41df20928f 100644
--- a/include/asm-arm/tlb.h
+++ b/include/asm-arm/tlb.h
@@ -39,8 +39,7 @@ DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
 static inline struct mmu_gather *
 tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
 {
-        int cpu = smp_processor_id();
-        struct mmu_gather *tlb = &per_cpu(mmu_gathers, cpu);
+        struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
 
         tlb->mm = mm;
         tlb->freed = 0;
@@ -65,6 +64,8 @@ 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 tlb_is_full_mm(struct mmu_gather *tlb)