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-rw-r--r--mm/memory.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 48c122d42ed7..fb5608a120ed 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -311,6 +311,21 @@ int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
if (!new)
return -ENOMEM;
+ /*
+ * Ensure all pte setup (eg. pte page lock and page clearing) are
+ * visible before the pte is made visible to other CPUs by being
+ * put into page tables.
+ *
+ * The other side of the story is the pointer chasing in the page
+ * table walking code (when walking the page table without locking;
+ * ie. most of the time). Fortunately, these data accesses consist
+ * of a chain of data-dependent loads, meaning most CPUs (alpha
+ * being the notable exception) will already guarantee loads are
+ * seen in-order. See the alpha page table accessors for the
+ * smp_read_barrier_depends() barriers in page table walking code.
+ */
+ smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
+
spin_lock(&mm->page_table_lock);
if (!pmd_present(*pmd)) { /* Has another populated it ? */
mm->nr_ptes++;
@@ -329,6 +344,8 @@ int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
if (!new)
return -ENOMEM;
+ smp_wmb(); /* See comment in __pte_alloc */
+
spin_lock(&init_mm.page_table_lock);
if (!pmd_present(*pmd)) { /* Has another populated it ? */
pmd_populate_kernel(&init_mm, pmd, new);
@@ -2619,6 +2636,8 @@ int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
if (!new)
return -ENOMEM;
+ smp_wmb(); /* See comment in __pte_alloc */
+
spin_lock(&mm->page_table_lock);
if (pgd_present(*pgd)) /* Another has populated it */
pud_free(mm, new);
@@ -2640,6 +2659,8 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
if (!new)
return -ENOMEM;
+ smp_wmb(); /* See comment in __pte_alloc */
+
spin_lock(&mm->page_table_lock);
#ifndef __ARCH_HAS_4LEVEL_HACK
if (pud_present(*pud)) /* Another has populated it */