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Subject[PATCH 12/21] 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>
---
include/asm-arm/tlb.h | 5 +++--
include/asm-arm26/tlb.h | 7 ++++---
include/asm-generic/tlb.h | 10 +++++-----
include/asm-ia64/tlb.h | 6 ++++--
include/asm-sparc64/tlb.h | 4 +++-
5 files changed, 19 insertions(+), 13 deletions(-)
--- mm11/include/asm-arm/tlb.h 2005-06-17 20:48:29.000000000 +0100
+++ mm12/include/asm-arm/tlb.h 2005-09-24 19:28:56.000000000 +0100
@@ -39,8 +39,7 @@ DECLARE_PER_CPU(struct mmu_gather, mmu_g
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, u

/* 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)
--- mm11/include/asm-arm26/tlb.h 2005-06-17 20:48:29.000000000 +0100
+++ mm12/include/asm-arm26/tlb.h 2005-09-24 19:28:56.000000000 +0100
@@ -17,13 +17,12 @@ struct mmu_gather {
unsigned int avoided_flushes;
};

-extern struct mmu_gather mmu_gathers[NR_CPUS];
+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 = &mmu_gathers[cpu];
+ struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);

tlb->mm = mm;
tlb->freed = 0;
@@ -52,6 +51,8 @@ tlb_finish_mmu(struct mmu_gather *tlb, u

/* keep the page table cache within bounds */
check_pgt_cache();
+
+ put_cpu_var(mmu_gathers);
}


--- mm11/include/asm-generic/tlb.h 2005-09-21 12:16:48.000000000 +0100
+++ mm12/include/asm-generic/tlb.h 2005-09-24 19:28:56.000000000 +0100
@@ -35,9 +35,7 @@
#endif

/* struct mmu_gather is an opaque type used by the mm code for passing around
- * any data needed by arch specific code for tlb_remove_page. This structure
- * can be per-CPU or per-MM as the page table lock is held for the duration of
- * TLB shootdown.
+ * any data needed by arch specific code for tlb_remove_page.
*/
struct mmu_gather {
struct mm_struct *mm;
@@ -57,7 +55,7 @@ DECLARE_PER_CPU(struct mmu_gather, mmu_g
static inline struct mmu_gather *
tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
{
- struct mmu_gather *tlb = &per_cpu(mmu_gathers, smp_processor_id());
+ struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);

tlb->mm = mm;

@@ -85,7 +83,7 @@ tlb_flush_mmu(struct mmu_gather *tlb, un

/* tlb_finish_mmu
* Called at the end of the shootdown operation to free up any resources
- * that were required. The page table lock is still held at this point.
+ * that were required.
*/
static inline void
tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
@@ -101,6 +99,8 @@ tlb_finish_mmu(struct mmu_gather *tlb, u

/* keep the page table cache within bounds */
check_pgt_cache();
+
+ put_cpu_var(mmu_gathers);
}

static inline unsigned int
--- mm11/include/asm-ia64/tlb.h 2005-06-17 20:48:29.000000000 +0100
+++ mm12/include/asm-ia64/tlb.h 2005-09-24 19:28:56.000000000 +0100
@@ -129,7 +129,7 @@ ia64_tlb_flush_mmu (struct mmu_gather *t
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, un

/*
* 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,

/* keep the page table cache within bounds */
check_pgt_cache();
+
+ put_cpu_var(mmu_gathers);
}

static inline unsigned int
--- mm11/include/asm-sparc64/tlb.h 2005-06-17 20:48:29.000000000 +0100
+++ mm12/include/asm-sparc64/tlb.h 2005-09-24 19:28:56.000000000 +0100
@@ -44,7 +44,7 @@ extern void flush_tlb_pending(void);

static inline struct mmu_gather *tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
{
- struct mmu_gather *mp = &__get_cpu_var(mmu_gathers);
+ struct mmu_gather *mp = &get_cpu_var(mmu_gathers);

BUG_ON(mp->tlb_nr);

@@ -97,6 +97,8 @@ static inline void tlb_finish_mmu(struct

/* 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 *mp)
-
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