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locking/mutex: clear MUTEX_FLAGS if wait_list is empty due to signal

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[ 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: 040a0a3710 ("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>
This commit is contained in:
Zqiang
2021-05-17 11:40:05 +08:00
committed by Greg Kroah-Hartman
parent 5dfed1be0e
commit e354e3744b
4 changed files with 17 additions and 11 deletions
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4
kernel/locking/mutex-debug.c
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@@ -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;
}