[PATCH] mm: fix a race condition under SMC + COW

[linux-2.6-microblaze.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 601159a..160f5b5 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1577,7 +1577,14 @@ gotten:
                entry = mk_pte(new_page, vma->vm_page_prot);
                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
                lazy_mmu_prot_update(entry);
-               ptep_establish(vma, address, page_table, entry);
+               /*
+                * Clear the pte entry and flush it first, before updating the
+                * pte with the new entry. This will avoid a race condition
+                * seen in the presence of one thread doing SMC and another
+                * thread doing COW.
+                */
+               ptep_clear_flush(vma, address, page_table);
+               set_pte_at(mm, address, page_table, entry);
                update_mmu_cache(vma, address, entry);
                lru_cache_add_active(new_page);
                page_add_new_anon_rmap(new_page, vma, address);