106 lines
3.8 KiB
Diff
106 lines
3.8 KiB
Diff
From 31aee2dc5cb0dde7da5a2cad0631c2ff64889b81 Mon Sep 17 00:00:00 2001
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Message-Id: <31aee2dc5cb0dde7da5a2cad0631c2ff64889b81.1601675153.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: Peter Zijlstra <peterz@infradead.org>
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Date: Mon, 30 Sep 2019 18:15:44 +0200
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Subject: [PATCH 304/333] locking/rtmutex: Clean ->pi_blocked_on in the error
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case
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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 0be4ea6e3ce693101be0fbd55a0cc7ce238ab2eb ]
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The function rt_mutex_wait_proxy_lock() cleans ->pi_blocked_on in case
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of failure (timeout, signal). The same cleanup is required in
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__rt_mutex_start_proxy_lock().
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In both the cases the tasks was interrupted by a signal or timeout while
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acquiring the lock and after the interruption it longer blocks on the
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lock.
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Fixes: 1a1fb985f2e2b ("futex: Handle early deadlock return correctly")
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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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 | 43 +++++++++++++++++++++++-----------------
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1 file changed, 25 insertions(+), 18 deletions(-)
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diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
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index 2a9bf2443acc..63b3d6f306fa 100644
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--- a/kernel/locking/rtmutex.c
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+++ b/kernel/locking/rtmutex.c
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@@ -2320,6 +2320,26 @@ void rt_mutex_proxy_unlock(struct rt_mutex *lock,
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rt_mutex_set_owner(lock, NULL);
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}
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+static void fixup_rt_mutex_blocked(struct rt_mutex *lock)
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+{
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+ struct task_struct *tsk = current;
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+ /*
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+ * RT has a problem here when the wait got interrupted by a timeout
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+ * or a signal. task->pi_blocked_on is still set. The task must
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+ * acquire the hash bucket lock when returning from this function.
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+ *
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+ * If the hash bucket lock is contended then the
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+ * BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in
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+ * task_blocks_on_rt_mutex() will trigger. This can be avoided by
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+ * clearing task->pi_blocked_on which removes the task from the
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+ * boosting chain of the rtmutex. That's correct because the task
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+ * is not longer blocked on it.
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+ */
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+ raw_spin_lock(&tsk->pi_lock);
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+ tsk->pi_blocked_on = NULL;
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+ raw_spin_unlock(&tsk->pi_lock);
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+}
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+
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/**
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* __rt_mutex_start_proxy_lock() - Start lock acquisition for another task
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* @lock: the rt_mutex to take
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@@ -2392,6 +2412,9 @@ int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
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ret = 0;
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}
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+ if (ret)
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+ fixup_rt_mutex_blocked(lock);
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+
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debug_rt_mutex_print_deadlock(waiter);
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return ret;
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@@ -2472,7 +2495,6 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
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struct hrtimer_sleeper *to,
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struct rt_mutex_waiter *waiter)
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{
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- struct task_struct *tsk = current;
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int ret;
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raw_spin_lock_irq(&lock->wait_lock);
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@@ -2484,23 +2506,8 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
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* have to fix that up.
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*/
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fixup_rt_mutex_waiters(lock);
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- /*
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- * RT has a problem here when the wait got interrupted by a timeout
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- * or a signal. task->pi_blocked_on is still set. The task must
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- * acquire the hash bucket lock when returning from this function.
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- *
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- * If the hash bucket lock is contended then the
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- * BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in
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- * task_blocks_on_rt_mutex() will trigger. This can be avoided by
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- * clearing task->pi_blocked_on which removes the task from the
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- * boosting chain of the rtmutex. That's correct because the task
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- * is not longer blocked on it.
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- */
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- if (ret) {
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- raw_spin_lock(&tsk->pi_lock);
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- tsk->pi_blocked_on = NULL;
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- raw_spin_unlock(&tsk->pi_lock);
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- }
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+ if (ret)
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+ fixup_rt_mutex_blocked(lock);
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raw_spin_unlock_irq(&lock->wait_lock);
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--
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2.17.1
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