[PATCH] lockdep: annotate ->mmap_sem

Teach special (recursive) locking code to the lock validator.  Has no effect
on non-lockdep kernels.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 7f48abdd7bb6..54953d8a6f17 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -193,7 +193,10 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 
         down_write(&oldmm->mmap_sem);
         flush_cache_mm(oldmm);
-        down_write(&mm->mmap_sem);
+        /*
+         * Not linked in yet - no deadlock potential:
+         */
+        down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 
         mm->locked_vm = 0;
         mm->mmap = NULL;