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author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2013-11-15 14:46:50 (GMT) |
---|---|---|
committer | Scott Wood <scottwood@freescale.com> | 2014-04-10 00:19:32 (GMT) |
commit | 6c9fe1cf1a3d8c68f104dd8472059890e3fc6d87 (patch) | |
tree | 256cf8dc34cb2f03c702a3cae0864fca84dd9120 /kernel/rtmutex.c | |
parent | 9621d858da62206b8f25d6d89502d6c7bee191af (diff) | |
download | linux-fsl-qoriq-6c9fe1cf1a3d8c68f104dd8472059890e3fc6d87.tar.xz |
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 "rt_spin_unlock_after_trylock_in_irq" 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>
Diffstat (limited to 'kernel/rtmutex.c')
-rw-r--r-- | kernel/rtmutex.c | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index 5aa004d..4057bc6 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -816,10 +816,8 @@ 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); @@ -838,6 +836,23 @@ 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); @@ -868,6 +883,13 @@ 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); @@ -1191,7 +1213,8 @@ 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)) { |