Messages in this thread Patch in this message | | | From | Davidlohr Bueso <> | Subject | [PATCH 2/2] locking/rwbase_rt: Lockless reader waking up a writer | Date | Wed, 1 Sep 2021 15:28:25 -0700 |
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As with the rest of our sleeping locks, use a wake_q to allow waking up the writer without having to hold the wait_lock across the operation. While this is ideally for batching wakeups, single wakeup usage as still shown to be beneficial vs the cost of try_to_wakeup when the lock is contended.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de> --- kernel/locking/rwbase_rt.c | 4 +++- kernel/sched/core.c | 16 +++++++++++++--- 2 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c index 4ba15088e640..3444bc709973 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_WAKE_Q(wake_q); raw_spin_lock_irq(&rtm->wait_lock); /* @@ -151,9 +152,10 @@ static void __sched __rwbase_read_unlock(struct rwbase_rt *rwb, */ owner = rt_mutex_owner(rtm); if (owner) - wake_up_state(owner, state); + wake_q_add(&wake_q, owner); raw_spin_unlock_irq(&rtm->wait_lock); + wake_up_q_state(&wake_q, state); } static __always_inline void rwbase_read_unlock(struct rwbase_rt *rwb, diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7fc3d22bc6d8..22c77742f1a7 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4151,7 +4151,7 @@ void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task) put_task_struct(task); } -void wake_up_q(struct wake_q_head *head) +static void __wake_up_q(struct wake_q_head *head, unsigned int state) { struct wake_q_node *node = head->first; @@ -4164,14 +4164,24 @@ void wake_up_q(struct wake_q_head *head) task->wake_q.next = NULL; /* - * wake_up_process() executes a full barrier, which pairs with + * try_to_wake_up() executes a full barrier, which pairs with * the queueing in wake_q_add() so as not to miss wakeups. */ - wake_up_process(task); + try_to_wake_up(task, state, 0); put_task_struct(task); } } +void wake_up_q(struct wake_q_head *head) +{ + __wake_up_q(head, TASK_NORMAL); +} + +void wake_up_q_state(struct wake_q_head *head, unsigned int state) +{ + __wake_up_q(head, state); +} + /* * Perform scheduler related setup for a newly forked process p. * p is forked by current. -- 2.26.2
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