67 lines
2.3 KiB
Diff
67 lines
2.3 KiB
Diff
From 45c5960cecfa238f87f94c7d9803d9216f40ca12 Mon Sep 17 00:00:00 2001
|
|
From: Thomas Gleixner <tglx@linutronix.de>
|
|
Date: Tue, 9 May 2017 17:11:10 +0200
|
|
Subject: [PATCH 180/365] futex/rtmutex: Cure RT double blocking issue
|
|
|
|
RT has a problem when the wait on a futex/rtmutex got interrupted by a
|
|
timeout or a signal. task->pi_blocked_on is still set when returning from
|
|
rt_mutex_wait_proxy_lock(). The task must acquire the hash bucket lock
|
|
after this.
|
|
|
|
If the hash bucket lock is contended then the
|
|
BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in
|
|
task_blocks_on_rt_mutex() will trigger.
|
|
|
|
This can be avoided by clearing task->pi_blocked_on in the return path of
|
|
rt_mutex_wait_proxy_lock() which removes the task from the boosting chain
|
|
of the rtmutex. That's correct because the task is not longer blocked on
|
|
it.
|
|
|
|
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Reported-by: Engleder Gerhard <eg@keba.com>
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
---
|
|
kernel/locking/rtmutex.c | 19 +++++++++++++++++++
|
|
1 file changed, 19 insertions(+)
|
|
|
|
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
|
|
index 42a91329b4cd..2674b3cfb70c 100644
|
|
--- a/kernel/locking/rtmutex.c
|
|
+++ b/kernel/locking/rtmutex.c
|
|
@@ -2388,6 +2388,7 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
|
|
struct hrtimer_sleeper *to,
|
|
struct rt_mutex_waiter *waiter)
|
|
{
|
|
+ struct task_struct *tsk = current;
|
|
int ret;
|
|
|
|
raw_spin_lock_irq(&lock->wait_lock);
|
|
@@ -2399,6 +2400,24 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
|
|
* have to fix that up.
|
|
*/
|
|
fixup_rt_mutex_waiters(lock);
|
|
+
|
|
+ /*
|
|
+ * RT has a problem here when the wait got interrupted by a timeout
|
|
+ * or a signal. task->pi_blocked_on is still set. The task must
|
|
+ * acquire the hash bucket lock when returning from this function.
|
|
+ *
|
|
+ * If the hash bucket lock is contended then the
|
|
+ * BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in
|
|
+ * task_blocks_on_rt_mutex() will trigger. This can be avoided by
|
|
+ * clearing task->pi_blocked_on which removes the task from the
|
|
+ * boosting chain of the rtmutex. That's correct because the task
|
|
+ * is not longer blocked on it.
|
|
+ */
|
|
+ if (ret) {
|
|
+ raw_spin_lock(&tsk->pi_lock);
|
|
+ tsk->pi_blocked_on = NULL;
|
|
+ raw_spin_unlock(&tsk->pi_lock);
|
|
+ }
|
|
raw_spin_unlock_irq(&lock->wait_lock);
|
|
|
|
return ret;
|
|
--
|
|
2.28.0
|
|
|