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 <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: "Paul E. McKenney" <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

kernel/locking/mutex.c

···
 }
 
 /*
- * after acquiring lock with fastpath or when we lost out in contested
+ * After acquiring lock with fastpath or when we lost out in contested
  * slowpath, set ctx and wake up any waiters so they can recheck.
  *
  * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set,
···
 	spin_unlock_mutex(&lock->base.wait_lock, flags);
 }
 
+/*
+ * After acquiring lock in the 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
 static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
···
 
 	if (use_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);