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Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull locking fix from Thomas Gleixner:
 "A fix for a state leak which was introduced in the recent rework of
  futex/rtmutex interaction"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex,rt_mutex: Fix rt_mutex_cleanup_proxy_lock()
This commit is contained in:
Linus Torvalds 2017-05-27 08:59:37 -07:00
commit 805f286907
1 changed files with 18 additions and 6 deletions
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24
kernel/locking/rtmutex.c
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@ -1785,12 +1785,14 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
int ret;
raw_spin_lock_irq(&lock->wait_lock);
set_current_state(TASK_INTERRUPTIBLE);
/* sleep on the mutex */
set_current_state(TASK_INTERRUPTIBLE);
ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
/*
* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
* have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock_irq(&lock->wait_lock);
return ret;
@ -1821,16 +1823,26 @@ bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
bool cleanup = false;
raw_spin_lock_irq(&lock->wait_lock);
/*
* Do an unconditional try-lock, this deals with the lock stealing
* state where __rt_mutex_futex_unlock() -> mark_wakeup_next_waiter()
* sets a NULL owner.
*
* We're not interested in the return value, because the subsequent
* test on rt_mutex_owner() will infer that. If the trylock succeeded,
* we will own the lock and it will have removed the waiter. If we
* failed the trylock, we're still not owner and we need to remove
* ourselves.
*/
try_to_take_rt_mutex(lock, current, waiter);
/*
* Unless we're the owner; we're still enqueued on the wait_list.
* So check if we became owner, if not, take us off the wait_list.
*/
if (rt_mutex_owner(lock) != current) {
remove_waiter(lock, waiter);
fixup_rt_mutex_waiters(lock);
cleanup = true;
}
/*
* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
* have to fix that up.