[patch V3 42/64] locking/ww_mutex: Abstract waiter iteration

Thomas Gleixner
2021-08-05T15:44:33Z

From: Peter Zijlstra <peterz@infradead.org>

Split out the waiter iteration functions so they can be substituted for a
rtmutex based ww_mutex later.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/locking/ww_mutex.h | 57 ++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 53 insertions(+), 4 deletions(-)
---
--- a/kernel/locking/ww_mutex.h
+++ b/kernel/locking/ww_mutex.h
@@ -1,5 +1,49 @@
/* SPDX-License-Identifier: GPL-2.0-only */

+static inline struct mutex_waiter *
+__ww_waiter_first(struct mutex *lock)
+{
+ struct mutex_waiter *w;
+
+ w = list_first_entry(&lock->wait_list, struct mutex_waiter, list);
+ if (list_entry_is_head(w, &lock->wait_list, list))
+ return NULL;
+
+ return w;
+}
+
+static inline struct mutex_waiter *
+__ww_waiter_next(struct mutex *lock, struct mutex_waiter *w)
+{
+ w = list_next_entry(w, list);
+ if (list_entry_is_head(w, &lock->wait_list, list))
+ return NULL;
+
+ return w;
+}
+
+static inline struct mutex_waiter *
+__ww_waiter_prev(struct mutex *lock, struct mutex_waiter *w)
+{
+ w = list_prev_entry(w, list);
+ if (list_entry_is_head(w, &lock->wait_list, list))
+ return NULL;
+
+ return w;
+}
+
+static inline struct mutex_waiter *
+__ww_waiter_last(struct mutex *lock)
+{
+ struct mutex_waiter *w;
+
+ w = list_last_entry(&lock->wait_list, struct mutex_waiter, list);
+ if (list_entry_is_head(w, &lock->wait_list, list))
+ return NULL;
+
+ return w;
+}
+
/*
* Wait-Die:
* The newer transactions are killed when:
@@ -161,7 +205,9 @@ static void

lockdep_assert_held(&lock->wait_lock);

- list_for_each_entry(cur, &lock->wait_list, list) {
+ for (cur = __ww_waiter_first(lock); cur;
+ cur = __ww_waiter_next(lock, cur)) {
+
if (!cur->ww_ctx)
continue;

@@ -263,8 +309,9 @@ static inline int
* If there is a waiter in front of us that has a context, then its
* stamp is earlier than ours and we must kill ourself.
*/
- cur = waiter;
- list_for_each_entry_continue_reverse(cur, &lock->wait_list, list) {
+ for (cur = __ww_waiter_prev(lock, waiter); cur;
+ cur = __ww_waiter_prev(lock, cur)) {
+
if (!cur->ww_ctx)
continue;

@@ -309,7 +356,9 @@ static inline int
* may wound the lock holder.
*/
pos = &lock->wait_list;
- list_for_each_entry_reverse(cur, &lock->wait_list, list) {
+ for (cur = __ww_waiter_last(lock); cur;
+ cur = __ww_waiter_prev(lock, cur)) {
+
if (!cur->ww_ctx)
continue;