[PATCH -mm 2/3] lockdep: mark rwsem_acquire_read as recursive

[Vladimir Davydov]

rw_semaphore implementation allows recursing calls to down_read, but
lockdep thinks that it doesn't. As a result, it will complain
false-positively, e.g. if we do not observe some predefined locking
order when taking an rw semaphore for reading and a mutex.

This patch makes lockdep think rw semaphore is read-recursive, just like
rw spin lock.

Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
---
 include/linux/lockdep.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 008388f920d7..4b95fe85375e 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -500,7 +500,7 @@ static inline void print_irqtrace_events(struct task_struct *curr)
 
 #define rwsem_acquire(l, s, t, i)		lock_acquire_exclusive(l, s, t, NULL, i)
 #define rwsem_acquire_nest(l, s, t, n, i)	lock_acquire_exclusive(l, s, t, n, i)
-#define rwsem_acquire_read(l, s, t, i)		lock_acquire_shared(l, s, t, NULL, i)
+#define rwsem_acquire_read(l, s, t, i)		lock_acquire_shared_recursive(l, s, t, NULL, i)
 #define rwsem_release(l, n, i)			lock_release(l, n, i)
 
 #define lock_map_acquire(l)			lock_acquire_exclusive(l, 0, 0, NULL, _THIS_IP_)
-- 
1.7.10.4

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