diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2021-09-28 17:00:06 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-10-01 13:57:52 +0200 |
| commit | 9321f8152d9a764208c3f0dad49e0c55f293b7ab (patch) | |
| tree | da2f8007e85e6ff75483bf78d5cc1cb388594cae /kernel/locking | |
| parent | 8fe46535e10dbfebad68ad9f2f8260e49f5852c9 (diff) | |
| download | linux-9321f8152d9a764208c3f0dad49e0c55f293b7ab.tar.gz | |
rtmutex: Wake up the waiters lockless while dropping the read lock.
The rw_semaphore and rwlock_t implementation both wake the waiter while
holding the rt_mutex_base::wait_lock acquired.
This can be optimized by waking the waiter lockless outside of the
locked section to avoid a needless contention on the
rt_mutex_base::wait_lock lock.
Extend rt_mutex_wake_q_add() to also accept task and state and use it in
__rwbase_read_unlock().
Suggested-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928150006.597310-3-bigeasy@linutronix.de
Diffstat (limited to 'kernel/locking')
| -rw-r--r-- | kernel/locking/rtmutex.c | 19 | ||||
| -rw-r--r-- | kernel/locking/rwbase_rt.c | 6 |
2 files changed, 18 insertions, 7 deletions
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index cafc259ec59d3..0c6a48dfcecb3 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -446,19 +446,26 @@ static __always_inline void rt_mutex_adjust_prio(struct task_struct *p) } /* RT mutex specific wake_q wrappers */ -static __always_inline void rt_mutex_wake_q_add(struct rt_wake_q_head *wqh, - struct rt_mutex_waiter *w) +static __always_inline void rt_mutex_wake_q_add_task(struct rt_wake_q_head *wqh, + struct task_struct *task, + unsigned int wake_state) { - if (IS_ENABLED(CONFIG_PREEMPT_RT) && w->wake_state == TASK_RTLOCK_WAIT) { + if (IS_ENABLED(CONFIG_PREEMPT_RT) && wake_state == TASK_RTLOCK_WAIT) { if (IS_ENABLED(CONFIG_PROVE_LOCKING)) WARN_ON_ONCE(wqh->rtlock_task); - get_task_struct(w->task); - wqh->rtlock_task = w->task; + get_task_struct(task); + wqh->rtlock_task = task; } else { - wake_q_add(&wqh->head, w->task); + wake_q_add(&wqh->head, task); } } +static __always_inline void rt_mutex_wake_q_add(struct rt_wake_q_head *wqh, + struct rt_mutex_waiter *w) +{ + rt_mutex_wake_q_add_task(wqh, w->task, w->wake_state); +} + static __always_inline void rt_mutex_wake_up_q(struct rt_wake_q_head *wqh) { if (IS_ENABLED(CONFIG_PREEMPT_RT) && wqh->rtlock_task) { diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c index 4ba15088e6405..6b143fb294f60 100644 --- a/kernel/locking/rwbase_rt.c +++ b/kernel/locking/rwbase_rt.c @@ -141,6 +141,7 @@ static void __sched __rwbase_read_unlock(struct rwbase_rt *rwb, { struct rt_mutex_base *rtm = &rwb->rtmutex; struct task_struct *owner; + DEFINE_RT_WAKE_Q(wqh); raw_spin_lock_irq(&rtm->wait_lock); /* @@ -151,9 +152,12 @@ static void __sched __rwbase_read_unlock(struct rwbase_rt *rwb, */ owner = rt_mutex_owner(rtm); if (owner) - wake_up_state(owner, state); + rt_mutex_wake_q_add_task(&wqh, owner, state); + /* Pairs with the preempt_enable in rt_mutex_wake_up_q() */ + preempt_disable(); raw_spin_unlock_irq(&rtm->wait_lock); + rt_mutex_wake_up_q(&wqh); } static __always_inline void rwbase_read_unlock(struct rwbase_rt *rwb, |