linux-kernel - [PATCH 5/8] locking/mutex: Introduce ww_mutex_set_context

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Date:	Sun, 28 Dec 2014 01:11:20 -0800
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH 5/8] locking/mutex: Introduce ww_mutex_set_context_slowpath

... which is equivalent to the fastpath counter part.
This mainly allows getting some ww specific code out
of generic mutex paths.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 kernel/locking/mutex.c | 43 ++++++++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 17 deletions(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index caa3c9f..5b6df69 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -155,7 +155,7 @@ static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
  */
 static __always_inline void
 ww_mutex_set_context_fastpath(struct ww_mutex *lock,
-			       struct ww_acquire_ctx *ctx)
+			      struct ww_acquire_ctx *ctx)
 {
 	unsigned long flags;
 	struct mutex_waiter *cur;
@@ -191,6 +191,30 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock,
 	spin_unlock_mutex(&lock->base.wait_lock, flags);
 }
 
+/*
+ * after acquiring lock in the slowpath or when we lost out in contested
+ * slowpath, set ctx and wake up any waiters so they can recheck.
+ *
+ * Callers must hold the mutex wait_lock.
+ */
+static __always_inline void
+ww_mutex_set_context_slowpath(struct ww_mutex *lock,
+			      struct ww_acquire_ctx *ctx)
+{
+	struct mutex_waiter *cur;
+
+	ww_mutex_lock_acquired(lock, ctx);
+	lock->ctx = ctx;
+
+	/*
+	 * Give any possible sleeping processes the chance to wake up,
+	 * so they can recheck if they have to back off.
+	 */
+	list_for_each_entry(cur, &lock->base.wait_list, list) {
+		debug_mutex_wake_waiter(lock->base, cur);
+		wake_up_process(cur->task);
+	}
+}
 
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
 /*
@@ -576,23 +600,8 @@ skip_wait:
 
 	if (ww_ctx) {
 		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
-		struct mutex_waiter *cur;
 
-		/*
-		 * This branch gets optimized out for the common case,
-		 * and is only important for ww_mutex_lock.
-		 */
-		ww_mutex_lock_acquired(ww, ww_ctx);
-		ww->ctx = ww_ctx;
-
-		/*
-		 * Give any possible sleeping processes the chance to wake up,
-		 * so they can recheck if they have to back off.
-		 */
-		list_for_each_entry(cur, &lock->wait_list, list) {
-			debug_mutex_wake_waiter(lock, cur);
-			wake_up_process(cur->task);
-		}
+		ww_mutex_set_context_slowpath(ww, ww_ctx);
 	}
 
 	spin_unlock_mutex(&lock->wait_lock, flags);
-- 
2.1.2

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