From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
John Kacur <jkacur@redhat.com>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Julia Cartwright <julia@ni.com>, Daniel Wagner <wagi@monom.org>,
tom.zanussi@linux.intel.com
Subject: [PATCH RT 10/16] Revert "futex: Fix bug on when a requeued RT task times out"
Date: Fri, 19 Jul 2019 17:49:41 -0400 [thread overview]
Message-ID: <20190719214957.604245348@goodmis.org> (raw)
In-Reply-To: 20190719214931.700049248@goodmis.org
4.19.59-rt24-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ 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 2a9bf2443acc..7f6f402e04ae 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;
}
/*
@@ -2350,34 +2349,6 @@ 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 546aaf058b9e..a501f3b47081 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,
--
2.20.1
next prev parent reply other threads:[~2019-07-19 21:50 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 21:49 [PATCH RT 00/16] Linux 4.19.59-rt24-rc1 Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 01/16] kthread: add a global worker thread Steven Rostedt
2019-07-22 8:30 ` Juri Lelli
2019-07-23 18:54 ` Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 02/16] genirq: Do not invoke the affinity callback via a workqueue on RT Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 03/16] genirq: Handle missing work_struct in irq_set_affinity_notifier() Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 04/16] arm: imx6: cpuidle: Use raw_spinlock_t Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 05/16] rcu: Dont allow to change rcu_normal_after_boot on RT Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 06/16] pci/switchtec: fix stream_open.cocci warnings Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 07/16] sched/core: Drop a preempt_disable_rt() statement Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 08/16] timers: Redo the notification of canceling timers on -RT Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 09/16] Revert "futex: Ensure lock/unlock symetry versus pi_lock and hash bucket lock" Steven Rostedt
2019-07-19 21:49 ` Steven Rostedt [this message]
2019-07-19 21:49 ` [PATCH RT 11/16] Revert "rtmutex: Handle the various new futex race conditions" Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 12/16] Revert "futex: workaround migrate_disable/enable in different context" Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 13/16] futex: Make the futex_hash_bucket lock raw Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 14/16] futex: Delay deallocation of pi_state Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 15/16] mm/zswap: Do not disable preemption in zswap_frontswap_store() Steven Rostedt
2019-07-19 21:49 ` [PATCH RT 16/16] Linux 4.19.59-rt24-rc1 Steven Rostedt
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