linux-kernel - [RFC PATCH-queue/locking/rfc 1/2] locking/mutex: Simplify some ww_mutex code in __mutex_lock

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Date:   Fri, 26 Aug 2016 19:35:08 -0400
From:   Waiman Long <Waiman.Long@....com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ding Tianhong <dingtianhong@...wei.com>,
        Jason Low <jason.low2@....com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E. McKenney" <paulmck@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <Will.Deacon@....com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Imre Deak <imre.deak@...el.com>,
        Waiman Long <Waiman.Long@....com>
Subject: [RFC PATCH-queue/locking/rfc 1/2] locking/mutex: Simplify some ww_mutex code in __mutex_lock_common()

This patch removes some of the redundant ww_mutex code in
__mutex_lock_common().

Signed-off-by: Waiman Long <Waiman.Long@....com>
---
 kernel/locking/mutex.c |   13 ++++---------
 1 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 0f8a3e6..4a0e16e 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -559,10 +559,11 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 	struct task_struct *task = current;
 	struct mutex_waiter waiter;
 	unsigned long flags;
+	struct ww_mutex *ww;
 	int ret;
 
 	if (use_ww_ctx) {
-		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
+		ww = container_of(lock, struct ww_mutex, base);
 		if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
 			return -EALREADY;
 	}
@@ -573,12 +574,8 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 	if (__mutex_trylock(lock) || mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx)) {
 		/* got the lock, yay! */
 		lock_acquired(&lock->dep_map, ip);
-		if (use_ww_ctx) {
-			struct ww_mutex *ww;
-			ww = container_of(lock, struct ww_mutex, base);
-
+		if (use_ww_ctx)
 			ww_mutex_set_context_fastpath(ww, ww_ctx);
-		}
 		preempt_enable();
 		return 0;
 	}
@@ -649,10 +646,8 @@ skip_wait:
 	/* got the lock - cleanup and rejoice! */
 	lock_acquired(&lock->dep_map, ip);
 
-	if (use_ww_ctx) {
-		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
+	if (use_ww_ctx)
 		ww_mutex_set_context_slowpath(ww, ww_ctx);
-	}
 
 	spin_unlock_mutex(&lock->wait_lock, flags);
 	preempt_enable();
-- 
1.7.1