linux-kernel - [PATCH 1/2] lockdep: Markup callers of might

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Message-Id: <20161211175201.12411-1-chris@chris-wilson.co.uk>
Date:   Sun, 11 Dec 2016 17:52:00 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     linux-kernel@...r.kernel.org
Cc:     intel-gfx@...ts.freedesktop.org,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: [PATCH 1/2] lockdep: Markup callers of might_lock() as potential sleepers

If might_lock() is called on a mutex, it may also potentially sleep.
Call might_sleep() in this case so that the caller is checked for both.
This is similar to the might_sleep() that is checked by the real
mutex_lock().

Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
---
 include/linux/lockdep.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index c1458fede1f9..0341e4246d00 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -549,9 +549,13 @@ static inline void print_irqtrace_events(struct task_struct *curr)
 #define lock_map_acquire_tryread(l)		lock_acquire_shared_recursive(l, 0, 1, NULL, _THIS_IP_)
 #define lock_map_release(l)			lock_release(l, 1, _THIS_IP_)
 
+#define lock_is_mutex(lock) \
+	__builtin_types_compatible_p(typeof(*lock), struct mutex)
+
 #ifdef CONFIG_PROVE_LOCKING
 # define might_lock(lock) 						\
 do {									\
+	might_sleep_if(lock_is_mutex(lock));				\
 	typecheck(struct lockdep_map *, &(lock)->dep_map);		\
 	lock_acquire(&(lock)->dep_map, 0, 0, 0, 1, NULL, _THIS_IP_);	\
 	lock_release(&(lock)->dep_map, 0, _THIS_IP_);			\
@@ -563,7 +567,9 @@ do {									\
 	lock_release(&(lock)->dep_map, 0, _THIS_IP_);			\
 } while (0)
 #else
-# define might_lock(lock) do { } while (0)
+# define might_lock(lock) do {						\
+	might_sleep_if(lock_is_mutex(lock));				\
+} while (0)
 # define might_lock_read(lock) do { } while (0)
 #endif
 
-- 
2.11.0