X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=mm%2Fmemory.c;h=fb5608a120edc77cffac3050ce7e5ebbcff94b8f;hb=a190901c6b5f1f4a31681e8c69d811a4f9426e2b;hp=bbab1e37055e22df235af61ddd201fe4b9832283;hpb=423bad600443c590f34ed7ce357591f76f48f137;p=safe%2Fjmp%2Flinux-2.6

diff --git a/mm/memory.c b/mm/memory.c
index bbab1e3..fb5608a 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);
@@ -969,7 +986,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 		goto no_page_table;
 	
 	pmd = pmd_offset(pud, address);
-	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
+	if (pmd_none(*pmd))
 		goto no_page_table;
 
 	if (pmd_huge(*pmd)) {
@@ -978,6 +995,9 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 		goto out;
 	}
 
+	if (unlikely(pmd_bad(*pmd)))
+		goto no_page_table;
+
 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
 	if (!ptep)
 		goto out;
@@ -2616,6 +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);
@@ -2637,6 +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 */