From: zanussi@kernel.org
To: LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>, John Kacur <jkacur@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Daniel Wagner <wagi@monom.org>, Tom Zanussi <zanussi@kernel.org>,
Julia Cartwright <julia@ni.com>
Subject: [PATCH RT 13/19] Revert "futex: Fix bug on when a requeued RT task times out"
Date: Thu, 8 Aug 2019 14:52:41 -0500 [thread overview]
Message-ID: <050713a32b125bb79ad609c7de0de98fd52db92a.1565293934.git.zanussi@kernel.org> (raw)
In-Reply-To: <cover.1565293934.git.zanussi@kernel.org>
In-Reply-To: <cover.1565293934.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
v4.14.137-rt65-rc1 stable review patch.
If anyone has any objections, please let me know.
-----------
[ 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: Tom Zanussi <zanussi@kernel.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 1177f2815040..62914dde3f1c 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;
}
/*
@@ -2358,34 +2357,6 @@ 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 2a157c78e18c..53ca0242101a 100644
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -132,7 +132,6 @@ 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,
--
2.14.1
next prev parent reply other threads:[~2019-08-08 19:54 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-08 19:52 [PATCH RT 00/19] Linux v4.14.137-rt65-rc1 zanussi
2019-08-08 19:52 ` [PATCH RT 01/19] kthread: Use __RAW_SPIN_LOCK_UNLOCK to initialize kthread_worker lock zanussi
2019-08-08 19:52 ` [PATCH RT 02/19] kthread: add a global worker thread zanussi
2019-08-08 19:52 ` [PATCH RT 03/19] genirq: Do not invoke the affinity callback via a workqueue on RT zanussi
2019-08-08 19:52 ` [PATCH RT 04/19] genirq: Handle missing work_struct in irq_set_affinity_notifier() zanussi
2019-08-08 19:52 ` [PATCH RT 05/19] locking/rwsem: Rename rwsem_rt.h to rwsem-rt.h zanussi
2019-08-08 19:52 ` [PATCH RT 06/19] sched/completion: Fix a lockup in wait_for_completion() zanussi
2019-08-08 19:52 ` [PATCH RT 07/19] locking/lockdep: Don't complain about incorrect name for no validate class zanussi
2019-08-08 19:52 ` [PATCH RT 08/19] arm: imx6: cpuidle: Use raw_spinlock_t zanussi
2019-08-08 19:52 ` [PATCH RT 09/19] rcu: Don't allow to change rcu_normal_after_boot on RT zanussi
2019-08-08 19:52 ` [PATCH RT 10/19] pci/switchtec: fix stream_open.cocci warnings zanussi
2019-08-08 19:52 ` [PATCH RT 11/19] sched/core: Drop a preempt_disable_rt() statement zanussi
2019-08-08 19:52 ` [PATCH RT 12/19] Revert "futex: Ensure lock/unlock symetry versus pi_lock and hash bucket lock" zanussi
2019-08-08 19:52 ` zanussi [this message]
2019-08-08 19:52 ` [PATCH RT 14/19] Revert "rtmutex: Handle the various new futex race conditions" zanussi
2019-08-08 19:52 ` [PATCH RT 15/19] Revert "futex: workaround migrate_disable/enable in different context" zanussi
2019-08-08 19:52 ` [PATCH RT 16/19] futex: Make the futex_hash_bucket lock raw zanussi
2019-08-08 19:52 ` [PATCH RT 17/19] futex: Delay deallocation of pi_state zanussi
2019-08-08 19:52 ` [PATCH RT 18/19] mm/zswap: Do not disable preemption in zswap_frontswap_store() zanussi
2019-08-08 19:52 ` [PATCH RT 19/19] Linux 4.14.137-rt65-rc1 zanussi
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