[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>

diff --git a/kernel/fork.c b/kernel/fork.c
index 7f48abdd7bb60336b245b897c61e94e9538fb05a..54953d8a6f175bb6c121da0a34949462264d3fdc 100644 (file)
--- 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;