locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after()

The function will be re-used in subsequent patches.

Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-4-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 24284497c42547ddcfbb1b8fe448a2968f334aa8..9ad03b9a5f7f3bbc57bef1201352dd9ad5856a2d 100644 (file)
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -281,6 +281,13 @@ static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
        ww_ctx->acquired++;
 }
 
+static inline bool __sched
+__ww_ctx_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.
@@ -597,8 +604,7 @@ __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_ctx_stamp_after(ctx, hold_ctx)) {
 #ifdef CONFIG_DEBUG_MUTEXES
                DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
                ctx->contending_lock = ww;