3.8.13.13-rt26-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Mike Galbraith captered the following:
| >#11 [ffff88017b243e90] _raw_spin_lock at ffffffff815d2596
| >#12 [ffff88017b243e90] rt_mutex_trylock at ffffffff815d15be
| >#13 [ffff88017b243eb0] get_next_timer_interrupt at ffffffff81063b42
| >#14 [ffff88017b243f00] tick_nohz_stop_sched_tick at ffffffff810bd1fd
| >#15 [ffff88017b243f70] tick_nohz_irq_exit at ffffffff810bd7d2
| >#16 [ffff88017b243f90] irq_exit at ffffffff8105b02d
| >#17 [ffff88017b243fb0] reschedule_interrupt at ffffffff815db3dd
| >--- <IRQ stack> ---
| >#18 [ffff88017a2a9bc8] reschedule_interrupt at ffffffff815db3dd
| > [exception RIP: task_blocks_on_rt_mutex+51]
| >#19 [ffff88017a2a9ce0] rt_spin_lock_slowlock at ffffffff815d183c
| >#20 [ffff88017a2a9da0] lock_timer_base.isra.35 at ffffffff81061cbf
| >#21 [ffff88017a2a9dd0] schedule_timeout at ffffffff815cf1ce
| >#22 [ffff88017a2a9e50] rcu_gp_kthread at ffffffff810f9bbb
| >#23 [ffff88017a2a9ed0] kthread at ffffffff810796d5
| >#24 [ffff88017a2a9f50] ret_from_fork at ffffffff815da04c
lock_timer_base() does a try_lock() which deadlocks on the waiter lock
not the lock itself.
This patch takes the waiter_lock with trylock so it should work from interrupt
context as well. If the fastpath doesn't work and the waiter_lock itself is
taken then it seems that the lock itself taken.
This patch also adds a "rt_spin_try_unlock" to keep lockdep happy. If we
managed to take the wait_lock in the first place we should also be able
to take it in the unlock path.
Cc: stable-rt@xxxxxxxxxxxxxxx
Reported-by: Mike Galbraith <bitbucket@xxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
include/linux/spinlock_rt.h | 1 +
kernel/rtmutex.c | 31 +++++++++++++++++++++++++++----
kernel/timer.c | 2 +-
3 files changed, 29 insertions(+), 5 deletions(-)
diff --git a/include/linux/spinlock_rt.h b/include/linux/spinlock_rt.h
index 0618387..b3c504b 100644
--- a/include/linux/spinlock_rt.h
+++ b/include/linux/spinlock_rt.h
@@ -22,6 +22,7 @@ extern void __lockfunc rt_spin_lock(spinlock_t *lock);
extern unsigned long __lockfunc rt_spin_lock_trace_flags(spinlock_t *lock);
extern void __lockfunc rt_spin_lock_nested(spinlock_t *lock, int subclass);
extern void __lockfunc rt_spin_unlock(spinlock_t *lock);
+extern void __lockfunc rt_spin_unlock_after_trylock_in_irq(spinlock_t *lock);
extern void __lockfunc rt_spin_unlock_wait(spinlock_t *lock);
extern int __lockfunc rt_spin_trylock_irqsave(spinlock_t *lock, unsigned long *flags);
extern int __lockfunc rt_spin_trylock_bh(spinlock_t *lock);
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 20742e7..3825e1c 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -801,10 +801,8 @@ static void noinline __sched rt_spin_lock_slowlock(struct rt_mutex *lock)
/*
* Slow path to release a rt_mutex spin_lock style
*/
-static void noinline __sched rt_spin_lock_slowunlock(struct rt_mutex *lock)
+static void __sched __rt_spin_lock_slowunlock(struct rt_mutex *lock)
{
- raw_spin_lock(&lock->wait_lock);
-
debug_rt_mutex_unlock(lock);
rt_mutex_deadlock_account_unlock(current);
@@ -823,6 +821,23 @@ static void noinline __sched rt_spin_lock_slowunlock(struct rt_mutex *lock)
rt_mutex_adjust_prio(current);
}
+static void noinline __sched rt_spin_lock_slowunlock(struct rt_mutex *lock)
+{
+ raw_spin_lock(&lock->wait_lock);
+ __rt_spin_lock_slowunlock(lock);
+}
+
+static void noinline __sched rt_spin_lock_slowunlock_hirq(struct rt_mutex *lock)
+{
+ int ret;
+
+ do {
+ ret = raw_spin_trylock(&lock->wait_lock);
+ } while (!ret);
+
+ __rt_spin_lock_slowunlock(lock);
+}
+
void __lockfunc rt_spin_lock(spinlock_t *lock)
{
rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
@@ -853,6 +868,13 @@ void __lockfunc rt_spin_unlock(spinlock_t *lock)
}
EXPORT_SYMBOL(rt_spin_unlock);
+void __lockfunc rt_spin_unlock_after_trylock_in_irq(spinlock_t *lock)
+{
+ /* NOTE: we always pass in '1' for nested, for simplicity */
+ spin_release(&lock->dep_map, 1, _RET_IP_);
+ rt_spin_lock_fastunlock(&lock->lock, rt_spin_lock_slowunlock_hirq);
+}
+
void __lockfunc __rt_spin_unlock(struct rt_mutex *lock)
{
rt_spin_lock_fastunlock(lock, rt_spin_lock_slowunlock);
@@ -1056,7 +1078,8 @@ rt_mutex_slowtrylock(struct rt_mutex *lock)
{
int ret = 0;
- raw_spin_lock(&lock->wait_lock);
+ if (!raw_spin_trylock(&lock->wait_lock))
+ return ret;
init_lists(lock);
if (likely(rt_mutex_owner(lock) != current)) {
diff --git a/kernel/timer.c b/kernel/timer.c
index 3bb957e..330221b 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1398,7 +1398,7 @@ unsigned long get_next_timer_interrupt(unsigned long now)
expires = base->next_timer;
}
#ifdef CONFIG_PREEMPT_RT_FULL
- rt_spin_unlock(&base->lock);
+ rt_spin_unlock_after_trylock_in_irq(&base->lock);
#else
spin_unlock(&base->lock);
#endif
--
1.8.4.3
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