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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 26 Jun 2019 17:44:18 +0200
Subject: [PATCH 272/351] Revert "futex: Fix bug on when a requeued RT task
times out"
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=b06b941626e30f9c6a9743a2a280d4592965bcf8
[ Upstream commit f1a170cb3289a48df26cae3c60d77608f7a988bb ]
Drop the RT fixup, the futex code will be changed to avoid the need for
the workaround.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/locking/rtmutex.c | 31 +------------------------------
kernel/locking/rtmutex_common.h | 1 -
2 files changed, 1 insertion(+), 31 deletions(-)
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index ded2296f848a..a87b65447991 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -144,8 +144,7 @@ static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
static int rt_mutex_real_waiter(struct rt_mutex_waiter *waiter)
{
- return waiter && waiter != PI_WAKEUP_INPROGRESS &&
- waiter != PI_REQUEUE_INPROGRESS;
+ return waiter && waiter != PI_WAKEUP_INPROGRESS;
}
/*
@@ -2349,34 +2348,6 @@ int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
if (try_to_take_rt_mutex(lock, task, NULL))
return 1;
-#ifdef CONFIG_PREEMPT_RT_FULL
- /*
- * In PREEMPT_RT there's an added race.
- * If the task, that we are about to requeue, times out,
- * it can set the PI_WAKEUP_INPROGRESS. This tells the requeue
- * to skip this task. But right after the task sets
- * its pi_blocked_on to PI_WAKEUP_INPROGRESS it can then
- * block on the spin_lock(&hb->lock), which in RT is an rtmutex.
- * This will replace the PI_WAKEUP_INPROGRESS with the actual
- * lock that it blocks on. We *must not* place this task
- * on this proxy lock in that case.
- *
- * To prevent this race, we first take the task's pi_lock
- * and check if it has updated its pi_blocked_on. If it has,
- * we assume that it woke up and we return -EAGAIN.
- * Otherwise, we set the task's pi_blocked_on to
- * PI_REQUEUE_INPROGRESS, so that if the task is waking up
- * it will know that we are in the process of requeuing it.
- */
- raw_spin_lock(&task->pi_lock);
- if (task->pi_blocked_on) {
- raw_spin_unlock(&task->pi_lock);
- return -EAGAIN;
- }
- task->pi_blocked_on = PI_REQUEUE_INPROGRESS;
- raw_spin_unlock(&task->pi_lock);
-#endif
-
/* We enforce deadlock detection for futexes */
ret = task_blocks_on_rt_mutex(lock, waiter, task,
RT_MUTEX_FULL_CHAINWALK);
diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
index 8e0c592273e6..627340e7427e 100644
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -133,7 +133,6 @@ enum rtmutex_chainwalk {
* PI-futex support (proxy locking functions, etc.):
*/
#define PI_WAKEUP_INPROGRESS ((struct rt_mutex_waiter *) 1)
-#define PI_REQUEUE_INPROGRESS ((struct rt_mutex_waiter *) 2)
extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
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