13b35686e8
The existing wait queue support has support for custom wake up call backs, wake flags, wake key (passed to call back) and exclusive flags that allow wakers to be tagged as exclusive, for limiting the number of wakers. In a lot of cases, none of these features are used, and hence we can benefit from a slimmed down version that lowers memory overhead and reduces runtime overhead. The concept originated from -rt, where waitqueues are a constant source of trouble, as we can't convert the head lock to a raw spinlock due to fancy and long lasting callbacks. With the removal of custom callbacks, we can use a raw lock for queue list manipulations, hence allowing the simple wait support to be used in -rt. [Patch is from PeterZ which is based on Thomas version. Commit message is written by Paul G. Daniel: - Fixed some compile issues - Added non-lazy implementation of swake_up_locked as suggested by Boqun Feng.] Originally-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: linux-rt-users@vger.kernel.org Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1455871601-27484-2-git-send-email-wagi@monom.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
124 lines
2.9 KiB
C
124 lines
2.9 KiB
C
#include <linux/sched.h>
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#include <linux/swait.h>
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void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
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struct lock_class_key *key)
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{
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raw_spin_lock_init(&q->lock);
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lockdep_set_class_and_name(&q->lock, key, name);
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INIT_LIST_HEAD(&q->task_list);
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}
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EXPORT_SYMBOL(__init_swait_queue_head);
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/*
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* The thing about the wake_up_state() return value; I think we can ignore it.
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*
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* If for some reason it would return 0, that means the previously waiting
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* task is already running, so it will observe condition true (or has already).
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*/
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void swake_up_locked(struct swait_queue_head *q)
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{
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struct swait_queue *curr;
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if (list_empty(&q->task_list))
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return;
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curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
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wake_up_process(curr->task);
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list_del_init(&curr->task_list);
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}
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EXPORT_SYMBOL(swake_up_locked);
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void swake_up(struct swait_queue_head *q)
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{
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unsigned long flags;
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if (!swait_active(q))
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return;
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raw_spin_lock_irqsave(&q->lock, flags);
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swake_up_locked(q);
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raw_spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(swake_up);
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/*
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* Does not allow usage from IRQ disabled, since we must be able to
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* release IRQs to guarantee bounded hold time.
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*/
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void swake_up_all(struct swait_queue_head *q)
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{
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struct swait_queue *curr;
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LIST_HEAD(tmp);
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if (!swait_active(q))
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return;
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raw_spin_lock_irq(&q->lock);
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list_splice_init(&q->task_list, &tmp);
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while (!list_empty(&tmp)) {
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curr = list_first_entry(&tmp, typeof(*curr), task_list);
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wake_up_state(curr->task, TASK_NORMAL);
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list_del_init(&curr->task_list);
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if (list_empty(&tmp))
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break;
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raw_spin_unlock_irq(&q->lock);
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raw_spin_lock_irq(&q->lock);
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}
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raw_spin_unlock_irq(&q->lock);
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}
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EXPORT_SYMBOL(swake_up_all);
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void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
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{
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wait->task = current;
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if (list_empty(&wait->task_list))
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list_add(&wait->task_list, &q->task_list);
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}
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void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&q->lock, flags);
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__prepare_to_swait(q, wait);
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set_current_state(state);
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raw_spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(prepare_to_swait);
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long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
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{
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if (signal_pending_state(state, current))
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return -ERESTARTSYS;
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prepare_to_swait(q, wait, state);
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return 0;
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}
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EXPORT_SYMBOL(prepare_to_swait_event);
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void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
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{
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__set_current_state(TASK_RUNNING);
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if (!list_empty(&wait->task_list))
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list_del_init(&wait->task_list);
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}
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void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
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{
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unsigned long flags;
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__set_current_state(TASK_RUNNING);
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if (!list_empty_careful(&wait->task_list)) {
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raw_spin_lock_irqsave(&q->lock, flags);
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list_del_init(&wait->task_list);
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raw_spin_unlock_irqrestore(&q->lock, flags);
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}
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}
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EXPORT_SYMBOL(finish_swait);
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