From 8ee62b1870be8e630158701632a533d0378e15b8 Mon Sep 17 00:00:00 2001
From: Jason Low <jason.low2@hpe.com>
Date: Fri, 3 Jun 2016 22:26:02 -0700
Subject: locking/rwsem: Convert sem->count to 'atomic_long_t'

Convert the rwsem count variable to an atomic_long_t since we use it
as an atomic variable. This also allows us to remove the
rwsem_atomic_{add,update}() "abstraction" which would now be an unnecesary
level of indirection. In follow up patches, we also remove the
rwsem_atomic_{add,update}() definitions across the various architectures.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jason Low <jason.low2@hpe.com>
[ Build warning fixes on various architectures. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Terry Rudd <terry.rudd@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Waiman Long <Waiman.Long@hpe.com>
Link: http://lkml.kernel.org/r/1465017963-4839-2-git-send-email-jason.low2@hpe.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/rwsem.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 'include/linux/rwsem.h')

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index d37fbb34d06f..dd1d14250340 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -23,10 +23,11 @@ struct rw_semaphore;
 
 #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
 #include <linux/rwsem-spinlock.h> /* use a generic implementation */
+#define __RWSEM_INIT_COUNT(name)	.count = RWSEM_UNLOCKED_VALUE
 #else
 /* All arch specific implementations share the same struct */
 struct rw_semaphore {
-	long count;
+	atomic_long_t count;
 	struct list_head wait_list;
 	raw_spinlock_t wait_lock;
 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
@@ -54,9 +55,10 @@ extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
 /* In all implementations count != 0 means locked */
 static inline int rwsem_is_locked(struct rw_semaphore *sem)
 {
-	return sem->count != 0;
+	return atomic_long_read(&sem->count) != 0;
 }
 
+#define __RWSEM_INIT_COUNT(name)	.count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
 #endif
 
 /* Common initializer macros and functions */
@@ -74,7 +76,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
 #endif
 
 #define __RWSEM_INITIALIZER(name)				\
-	{ .count = RWSEM_UNLOCKED_VALUE,			\
+	{ __RWSEM_INIT_COUNT(name),				\
 	  .wait_list = LIST_HEAD_INIT((name).wait_list),	\
 	  .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock)	\
 	  __RWSEM_OPT_INIT(name)				\
-- 
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