--- /dev/null
+From 8ec34f007b392032744ea14e9f6f68579c3601bc Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Mon, 17 May 2021 11:40:05 +0800
+Subject: locking/mutex: clear MUTEX_FLAGS if wait_list is empty due to signal
+
+From: Zqiang <qiang.zhang@windriver.com>
+
+[ Upstream commit 3a010c493271f04578b133de977e0e5dd2848cea ]
+
+When a interruptible mutex locker is interrupted by a signal
+without acquiring this lock and removed from the wait queue.
+if the mutex isn't contended enough to have a waiter
+put into the wait queue again, the setting of the WAITER
+bit will force mutex locker to go into the slowpath to
+acquire the lock every time, so if the wait queue is empty,
+the WAITER bit need to be clear.
+
+Fixes: 040a0a371005 ("mutex: Add support for wound/wait style locks")
+Suggested-by: Peter Zijlstra <peterz@infradead.org>
+Signed-off-by: Zqiang <qiang.zhang@windriver.com>
+Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
+Link: https://lkml.kernel.org/r/20210517034005.30828-1-qiang.zhang@windriver.com
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ kernel/locking/mutex-debug.c | 4 ++--
+ kernel/locking/mutex-debug.h | 2 +-
+ kernel/locking/mutex.c | 18 +++++++++++++-----
+ kernel/locking/mutex.h | 4 +---
+ 4 files changed, 17 insertions(+), 11 deletions(-)
+
+diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
+index 9aa713629387..839df4383799 100644
+--- a/kernel/locking/mutex-debug.c
++++ b/kernel/locking/mutex-debug.c
+@@ -57,7 +57,7 @@ void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+ task->blocked_on = waiter;
+ }
+
+-void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
++void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+ struct task_struct *task)
+ {
+ DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list));
+@@ -65,7 +65,7 @@ void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+ DEBUG_LOCKS_WARN_ON(task->blocked_on != waiter);
+ task->blocked_on = NULL;
+
+- list_del_init(&waiter->list);
++ INIT_LIST_HEAD(&waiter->list);
+ waiter->task = NULL;
+ }
+
+diff --git a/kernel/locking/mutex-debug.h b/kernel/locking/mutex-debug.h
+index 1edd3f45a4ec..53e631e1d76d 100644
+--- a/kernel/locking/mutex-debug.h
++++ b/kernel/locking/mutex-debug.h
+@@ -22,7 +22,7 @@ extern void debug_mutex_free_waiter(struct mutex_waiter *waiter);
+ extern void debug_mutex_add_waiter(struct mutex *lock,
+ struct mutex_waiter *waiter,
+ struct task_struct *task);
+-extern void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
++extern void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+ struct task_struct *task);
+ extern void debug_mutex_unlock(struct mutex *lock);
+ extern void debug_mutex_init(struct mutex *lock, const char *name,
+diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
+index b3da782cdfbd..354151fef06a 100644
+--- a/kernel/locking/mutex.c
++++ b/kernel/locking/mutex.c
+@@ -177,7 +177,7 @@ static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_wait
+ * Add @waiter to a given location in the lock wait_list and set the
+ * FLAG_WAITERS flag if it's the first waiter.
+ */
+-static void __sched
++static void
+ __mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+ struct list_head *list)
+ {
+@@ -188,6 +188,16 @@ __mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+ __mutex_set_flag(lock, MUTEX_FLAG_WAITERS);
+ }
+
++static void
++__mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter)
++{
++ list_del(&waiter->list);
++ if (likely(list_empty(&lock->wait_list)))
++ __mutex_clear_flag(lock, MUTEX_FLAGS);
++
++ debug_mutex_remove_waiter(lock, waiter, current);
++}
++
+ /*
+ * Give up ownership to a specific task, when @task = NULL, this is equivalent
+ * to a regular unlock. Sets PICKUP on a handoff, clears HANDOF, preserves
+@@ -1040,9 +1050,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
+ __ww_mutex_check_waiters(lock, ww_ctx);
+ }
+
+- mutex_remove_waiter(lock, &waiter, current);
+- if (likely(list_empty(&lock->wait_list)))
+- __mutex_clear_flag(lock, MUTEX_FLAGS);
++ __mutex_remove_waiter(lock, &waiter);
+
+ debug_mutex_free_waiter(&waiter);
+
+@@ -1059,7 +1067,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
+
+ err:
+ __set_current_state(TASK_RUNNING);
+- mutex_remove_waiter(lock, &waiter, current);
++ __mutex_remove_waiter(lock, &waiter);
+ err_early_kill:
+ spin_unlock(&lock->wait_lock);
+ debug_mutex_free_waiter(&waiter);
+diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h
+index 1c2287d3fa71..f0c710b1d192 100644
+--- a/kernel/locking/mutex.h
++++ b/kernel/locking/mutex.h
+@@ -10,12 +10,10 @@
+ * !CONFIG_DEBUG_MUTEXES case. Most of them are NOPs:
+ */
+
+-#define mutex_remove_waiter(lock, waiter, task) \
+- __list_del((waiter)->list.prev, (waiter)->list.next)
+-
+ #define debug_mutex_wake_waiter(lock, waiter) do { } while (0)
+ #define debug_mutex_free_waiter(waiter) do { } while (0)
+ #define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0)
++#define debug_mutex_remove_waiter(lock, waiter, ti) do { } while (0)
+ #define debug_mutex_unlock(lock) do { } while (0)
+ #define debug_mutex_init(lock, name, key) do { } while (0)
+
+--
+2.30.2
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
