locking/csd_lock: Explicitly inline csd_lock*() helpers

While the compiler tends to already to it for us (except for
csd_unlock), make it explicit. These helpers mainly deal with
the ->flags, are short-lived  and can be called, for example,
from smp_call_function_many().

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Link: http://lkml.kernel.org/r/1457574936-19065-2-git-send-email-dbueso@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/smp.c

@@ -105,13 +105,13 @@ void __init call_function_init(void)
  * previous function call. For multi-cpu calls its even more interesting
  * as we'll have to ensure no other cpu is observing our csd.
  */
-static void csd_lock_wait(struct call_single_data *csd)
+static __always_inline void csd_lock_wait(struct call_single_data *csd)
 {
 	while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK)
 		cpu_relax();
 }
 
-static void csd_lock(struct call_single_data *csd)
+static __always_inline void csd_lock(struct call_single_data *csd)
 {
 	csd_lock_wait(csd);
 	csd->flags |= CSD_FLAG_LOCK;
@@ -124,7 +124,7 @@ static void csd_lock(struct call_single_data *csd)
 	smp_wmb();
 }
 
-static void csd_unlock(struct call_single_data *csd)
+static __always_inline void csd_unlock(struct call_single_data *csd)
 {
 	WARN_ON(!(csd->flags & CSD_FLAG_LOCK));