diff options
author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2013-11-15 15:46:50 +0100 |
---|---|---|
committer | Steven Rostedt <rostedt@rostedt.homelinux.com> | 2014-01-16 09:38:02 -0500 |
commit | e4d81192dd5f2d218bf085cfa3a5821604ff116d (patch) | |
tree | 04bb620ffaf7a29c84cb6654fa470a509ca827f1 | |
parent | 4769ed10f0332b7a62b89a7a906ac09bffe59e46 (diff) |
rtmutex: use a trylock for waiter lock in trylock
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@vger.kernel.org
Reported-by: Mike Galbraith <bitbucket@online.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
-rw-r--r-- | include/linux/spinlock_rt.h | 1 | ||||
-rw-r--r-- | kernel/rtmutex.c | 31 | ||||
-rw-r--r-- | 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 06183876ee96..b3c504bb9852 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 20742e7d4509..3825e1cef591 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 78f07e5a0bdf..fb1c00ddd30d 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1386,7 +1386,7 @@ unsigned long get_next_timer_interrupt(unsigned long now) if (time_before_eq(base->next_timer, base->timer_jiffies)) base->next_timer = __next_timer_interrupt(base); expires = base->next_timer; - rt_spin_unlock(&base->lock); + rt_spin_unlock_after_trylock_in_irq(&base->lock); } else { expires = now + 1; } |