linux-kernel - [PATCH 03/11] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp

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Date:   Mon, 28 Nov 2016 13:20:04 +0100
From:   Nicolai Hähnle <nhaehnle@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Nicolai Hähnle <Nicolai.Haehnle@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Maarten Lankhorst <dev@...ankhorst.nl>,
        Daniel Vetter <daniel@...ll.ch>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH 03/11] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after

From: Nicolai Hähnle <Nicolai.Haehnle@....com>

The function will be re-used in subsequent patches.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Maarten Lankhorst <dev@...ankhorst.nl>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: dri-devel@...ts.freedesktop.org
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@....com>
---
 kernel/locking/mutex.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 0afa998..200629a 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -277,6 +277,13 @@ static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
 	ww_ctx->acquired++;
 }
 
+static inline bool __sched
+__ww_mutex_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
+{
+	return a->stamp - b->stamp <= LONG_MAX &&
+	       (a->stamp != b->stamp || a > b);
+}
+
 /*
  * After acquiring lock with fastpath or when we lost out in contested
  * slowpath, set ctx and wake up any waiters so they can recheck.
@@ -610,8 +617,7 @@ __ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
 	if (!hold_ctx)
 		return 0;
 
-	if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
-	    (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
+	if (__ww_mutex_stamp_after(ctx, hold_ctx)) {
 #ifdef CONFIG_DEBUG_MUTEXES
 		DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
 		ctx->contending_lock = ww;
-- 
2.7.4