Linus,
please pull the latest locking-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
locking-urgent-for-linus
A fix for a state leak which was introduced in the recent rework of
futex/rtmutex interaction.
Thanks,
tglx
------------------>
Peter Zijlstra (1):
futex,rt_mutex: Fix rt_mutex_cleanup_proxy_lock()
kernel/locking/rtmutex.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index b95509416909..28cd09e635ed 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -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;
@@ -1822,15 +1824,25 @@ bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
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.
