87 lines
3.4 KiB
Diff
87 lines
3.4 KiB
Diff
From 15abc655043f26817b3bf2bd43c8cd1c9d0821d6 Mon Sep 17 00:00:00 2001
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Message-Id: <15abc655043f26817b3bf2bd43c8cd1c9d0821d6.1601675153.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 26 Jun 2019 17:44:18 +0200
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Subject: [PATCH 273/333] Revert "futex: Fix bug on when a requeued RT task
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times out"
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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[ Upstream commit f1a170cb3289a48df26cae3c60d77608f7a988bb ]
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Drop the RT fixup, the futex code will be changed to avoid the need for
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the workaround.
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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---
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kernel/locking/rtmutex.c | 31 +------------------------------
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kernel/locking/rtmutex_common.h | 1 -
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2 files changed, 1 insertion(+), 31 deletions(-)
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diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
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index 2a9bf2443acc..7f6f402e04ae 100644
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--- a/kernel/locking/rtmutex.c
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+++ b/kernel/locking/rtmutex.c
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@@ -144,8 +144,7 @@ static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
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static int rt_mutex_real_waiter(struct rt_mutex_waiter *waiter)
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{
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- return waiter && waiter != PI_WAKEUP_INPROGRESS &&
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- waiter != PI_REQUEUE_INPROGRESS;
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+ return waiter && waiter != PI_WAKEUP_INPROGRESS;
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}
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/*
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@@ -2350,34 +2349,6 @@ int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
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if (try_to_take_rt_mutex(lock, task, NULL))
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return 1;
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-#ifdef CONFIG_PREEMPT_RT_FULL
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- /*
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- * In PREEMPT_RT there's an added race.
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- * If the task, that we are about to requeue, times out,
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- * it can set the PI_WAKEUP_INPROGRESS. This tells the requeue
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- * to skip this task. But right after the task sets
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- * its pi_blocked_on to PI_WAKEUP_INPROGRESS it can then
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- * block on the spin_lock(&hb->lock), which in RT is an rtmutex.
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- * This will replace the PI_WAKEUP_INPROGRESS with the actual
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- * lock that it blocks on. We *must not* place this task
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- * on this proxy lock in that case.
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- *
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- * To prevent this race, we first take the task's pi_lock
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- * and check if it has updated its pi_blocked_on. If it has,
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- * we assume that it woke up and we return -EAGAIN.
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- * Otherwise, we set the task's pi_blocked_on to
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- * PI_REQUEUE_INPROGRESS, so that if the task is waking up
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- * it will know that we are in the process of requeuing it.
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- */
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- raw_spin_lock(&task->pi_lock);
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- if (task->pi_blocked_on) {
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- raw_spin_unlock(&task->pi_lock);
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- return -EAGAIN;
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- }
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- task->pi_blocked_on = PI_REQUEUE_INPROGRESS;
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- raw_spin_unlock(&task->pi_lock);
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-#endif
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-
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/* We enforce deadlock detection for futexes */
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ret = task_blocks_on_rt_mutex(lock, waiter, task,
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RT_MUTEX_FULL_CHAINWALK);
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diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
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index 546aaf058b9e..a501f3b47081 100644
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--- a/kernel/locking/rtmutex_common.h
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+++ b/kernel/locking/rtmutex_common.h
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@@ -133,7 +133,6 @@ enum rtmutex_chainwalk {
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* PI-futex support (proxy locking functions, etc.):
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*/
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#define PI_WAKEUP_INPROGRESS ((struct rt_mutex_waiter *) 1)
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-#define PI_REQUEUE_INPROGRESS ((struct rt_mutex_waiter *) 2)
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extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
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extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
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--
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2.17.1
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