sched: Turn lock_task_sighand() into a static inline

It appears that sparse tool understands static inline functions
for context balance checking, so let's turn the macros into an
inline func.

This makes the code a little bit more robust.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Arve <arve@android.com>
Cc: San Mehat <san@google.com>
Cc: Colin Cross <ccross@android.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: kernel-team@android.com
Cc: linaro-kernel@lists.linaro.org
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120209164519.GA10266@oksana.dev.rtsoft.ru
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -2393,12 +2393,15 @@ static inline void task_unlock(struct task_struct *p)
 extern struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
 							unsigned long *flags);
 
-#define lock_task_sighand(tsk, flags)					\
-({	struct sighand_struct *__ss;					\
-	__cond_lock(&(tsk)->sighand->siglock,				\
-		    (__ss = __lock_task_sighand(tsk, flags)));		\
-	__ss;								\
-})									\
+static inline struct sighand_struct *lock_task_sighand(struct task_struct *tsk,
+						       unsigned long *flags)
+{
+	struct sighand_struct *ret;
+
+	ret = __lock_task_sighand(tsk, flags);
+	(void)__cond_lock(&tsk->sighand->siglock, ret);
+	return ret;
+}
 
 static inline void unlock_task_sighand(struct task_struct *tsk,
 						unsigned long *flags)