Merge ssh://master.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-x86

* ssh://master.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-x86:
  x86: fix global_flush_tlb() bug

1 files changed, 7 insertions, 2 deletions

diff --git a/arch/x86/mm/pageattr_64.c b/arch/x86/mm/pageattr_64.c
index 8a4f65bf956..c7b7dfe1d40 100644
--- a/arch/x86/mm/pageattr_64.c
+++ b/arch/x86/mm/pageattr_64.c
@@ -230,9 +230,14 @@ void global_flush_tlb(void)
 	struct page *pg, *next;
 	struct list_head l;
 
-	down_read(&init_mm.mmap_sem);
+	/*
+	 * Write-protect the semaphore, to exclude two contexts
+	 * doing a list_replace_init() call in parallel and to
+	 * exclude new additions to the deferred_pages list:
+	 */
+	down_write(&init_mm.mmap_sem);
 	list_replace_init(&deferred_pages, &l);
-	up_read(&init_mm.mmap_sem);
+	up_write(&init_mm.mmap_sem);
 
 	flush_map(&l);