126 lines
4.7 KiB
Diff
126 lines
4.7 KiB
Diff
From c290567d076d3b59d30c6778bc3f2e401d8289fe Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Fri, 15 Nov 2013 15:46:50 +0100
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Subject: [PATCH] rtmutex: use a trylock for waiter lock in trylock
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.12/patches-3.12.1-rt4.tar.xz
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Mike Galbraith captered the following:
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| >#11 [ffff88017b243e90] _raw_spin_lock at ffffffff815d2596
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| >#12 [ffff88017b243e90] rt_mutex_trylock at ffffffff815d15be
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| >#13 [ffff88017b243eb0] get_next_timer_interrupt at ffffffff81063b42
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| >#14 [ffff88017b243f00] tick_nohz_stop_sched_tick at ffffffff810bd1fd
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| >#15 [ffff88017b243f70] tick_nohz_irq_exit at ffffffff810bd7d2
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| >#16 [ffff88017b243f90] irq_exit at ffffffff8105b02d
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| >#17 [ffff88017b243fb0] reschedule_interrupt at ffffffff815db3dd
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| >--- <IRQ stack> ---
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| >#18 [ffff88017a2a9bc8] reschedule_interrupt at ffffffff815db3dd
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| > [exception RIP: task_blocks_on_rt_mutex+51]
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| >#19 [ffff88017a2a9ce0] rt_spin_lock_slowlock at ffffffff815d183c
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| >#20 [ffff88017a2a9da0] lock_timer_base.isra.35 at ffffffff81061cbf
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| >#21 [ffff88017a2a9dd0] schedule_timeout at ffffffff815cf1ce
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| >#22 [ffff88017a2a9e50] rcu_gp_kthread at ffffffff810f9bbb
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| >#23 [ffff88017a2a9ed0] kthread at ffffffff810796d5
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| >#24 [ffff88017a2a9f50] ret_from_fork at ffffffff815da04c
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lock_timer_base() does a try_lock() which deadlocks on the waiter lock
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not the lock itself.
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This patch takes the waiter_lock with trylock so it should work from interrupt
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context as well. If the fastpath doesn't work and the waiter_lock itself is
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taken then it seems that the lock itself taken.
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This patch also adds a "rt_spin_try_unlock" to keep lockdep happy. If we
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managed to take the wait_lock in the first place we should also be able
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to take it in the unlock path.
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Cc: stable-rt@vger.kernel.org
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Reported-by: Mike Galbraith <bitbucket@online.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/spinlock_rt.h | 1 +
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kernel/rtmutex.c | 31 +++++++++++++++++++++++++++----
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kernel/timer.c | 2 +-
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3 files changed, 29 insertions(+), 5 deletions(-)
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--- a/include/linux/spinlock_rt.h
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+++ b/include/linux/spinlock_rt.h
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@@ -22,6 +22,7 @@ extern void __lockfunc rt_spin_lock(spin
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extern unsigned long __lockfunc rt_spin_lock_trace_flags(spinlock_t *lock);
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extern void __lockfunc rt_spin_lock_nested(spinlock_t *lock, int subclass);
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extern void __lockfunc rt_spin_unlock(spinlock_t *lock);
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+extern void __lockfunc rt_spin_unlock_after_trylock_in_irq(spinlock_t *lock);
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extern void __lockfunc rt_spin_unlock_wait(spinlock_t *lock);
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extern int __lockfunc rt_spin_trylock_irqsave(spinlock_t *lock, unsigned long *flags);
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extern int __lockfunc rt_spin_trylock_bh(spinlock_t *lock);
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--- a/kernel/rtmutex.c
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+++ b/kernel/rtmutex.c
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@@ -816,10 +816,8 @@ static void noinline __sched rt_spin_lo
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/*
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* Slow path to release a rt_mutex spin_lock style
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*/
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-static void noinline __sched rt_spin_lock_slowunlock(struct rt_mutex *lock)
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+static void __sched __rt_spin_lock_slowunlock(struct rt_mutex *lock)
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{
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- raw_spin_lock(&lock->wait_lock);
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-
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debug_rt_mutex_unlock(lock);
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rt_mutex_deadlock_account_unlock(current);
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@@ -838,6 +836,23 @@ static void noinline __sched rt_spin_lo
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rt_mutex_adjust_prio(current);
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}
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+static void noinline __sched rt_spin_lock_slowunlock(struct rt_mutex *lock)
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+{
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+ raw_spin_lock(&lock->wait_lock);
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+ __rt_spin_lock_slowunlock(lock);
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+}
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+
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+static void noinline __sched rt_spin_lock_slowunlock_hirq(struct rt_mutex *lock)
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+{
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+ int ret;
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+
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+ do {
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+ ret = raw_spin_trylock(&lock->wait_lock);
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+ } while (!ret);
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+
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+ __rt_spin_lock_slowunlock(lock);
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+}
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+
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void __lockfunc rt_spin_lock(spinlock_t *lock)
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{
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rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
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@@ -868,6 +883,13 @@ void __lockfunc rt_spin_unlock(spinlock_
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}
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EXPORT_SYMBOL(rt_spin_unlock);
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+void __lockfunc rt_spin_unlock_after_trylock_in_irq(spinlock_t *lock)
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+{
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+ /* NOTE: we always pass in '1' for nested, for simplicity */
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+ spin_release(&lock->dep_map, 1, _RET_IP_);
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+ rt_spin_lock_fastunlock(&lock->lock, rt_spin_lock_slowunlock_hirq);
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+}
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+
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void __lockfunc __rt_spin_unlock(struct rt_mutex *lock)
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{
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rt_spin_lock_fastunlock(lock, rt_spin_lock_slowunlock);
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@@ -1191,7 +1213,8 @@ rt_mutex_slowtrylock(struct rt_mutex *lo
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{
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int ret = 0;
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- raw_spin_lock(&lock->wait_lock);
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+ if (!raw_spin_trylock(&lock->wait_lock))
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+ return ret;
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init_lists(lock);
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if (likely(rt_mutex_owner(lock) != current)) {
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--- a/kernel/timer.c
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+++ b/kernel/timer.c
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@@ -1400,7 +1400,7 @@ unsigned long get_next_timer_interrupt(u
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expires = base->next_timer;
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}
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#ifdef CONFIG_PREEMPT_RT_FULL
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- rt_spin_unlock(&base->lock);
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+ rt_spin_unlock_after_trylock_in_irq(&base->lock);
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#else
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spin_unlock(&base->lock);
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#endif
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