[PATCH] lockdep: fix seqlock_init()

seqlock_init() needs to use spin_lock_init() for dynamic locks, so that
lockdep is notified about the presence of a new lock.

(this is a fallout of the recent networking merge, which started using
the so-far unused seqlock_init() API.)

This fix solves the following lockdep-internal warning on current -git:

 INFO: trying to register non-static key.
 the code is fine but needs lockdep annotation.
 turning off the locking correctness validator.
     __lock_acquire+0x10c/0x9f9
     lock_acquire+0x56/0x72
     _spin_lock+0x35/0x42
     neigh_destroy+0x9d/0x12e
     neigh_periodic_timer+0x10a/0x15c
     run_timer_softirq+0x126/0x18e
     __do_softirq+0x6b/0xe6
     do_softirq+0x64/0xd2
     ksoftirqd+0x82/0x138

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 46000936f8f1..6b0648cfdffc 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -44,8 +44,11 @@ typedef struct {
 #define SEQLOCK_UNLOCKED \
                  __SEQLOCK_UNLOCKED(old_style_seqlock_init)
 
-#define seqlock_init(x) \
-                do { *(x) = (seqlock_t) __SEQLOCK_UNLOCKED(x); } while (0)
+#define seqlock_init(x)                                 \
+        do {                                            \
+                (x)->sequence = 0;                      \
+                spin_lock_init(&(x)->lock);             \
+        } while (0)
 
 #define DEFINE_SEQLOCK(x) \
                 seqlock_t x = __SEQLOCK_UNLOCKED(x)