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![Andrei Vagin](/assets/img/avatar_default.png)
Add complete_on_current_cpu, wake_up_poll_on_current_cpu helpers to wake up tasks on the current CPU. These two helpers are useful when the task needs to make a synchronous context switch to another task. In this context, synchronous means it wakes up the target task and falls asleep right after that. One example of such workloads is seccomp user notifies. This mechanism allows the supervisor process handles system calls on behalf of a target process. While the supervisor is handling an intercepted system call, the target process will be blocked in the kernel, waiting for a response to come back. On-CPU context switches are much faster than regular ones. Signed-off-by: Andrei Vagin <avagin@google.com> Acked-by: "Peter Zijlstra (Intel)" <peterz@infradead.org> Link: https://lore.kernel.org/r/20230308073201.3102738-4-avagin@google.com Signed-off-by: Kees Cook <keescook@chromium.org>
145 lines
3.6 KiB
C
145 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* <linux/swait.h> (simple wait queues ) implementation:
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*/
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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, int wake_flags)
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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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try_to_wake_up(curr->task, TASK_NORMAL, wake_flags);
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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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/*
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* Wake up all waiters. This is an interface which is solely exposed for
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* completions and not for general usage.
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*
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* It is intentionally different from swake_up_all() to allow usage from
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* hard interrupt context and interrupt disabled regions.
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*/
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void swake_up_all_locked(struct swait_queue_head *q)
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{
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while (!list_empty(&q->task_list))
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swake_up_locked(q, 0);
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}
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void swake_up_one(struct swait_queue_head *q)
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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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swake_up_locked(q, 0);
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raw_spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(swake_up_one);
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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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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_tail(&wait->task_list, &q->task_list);
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}
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void prepare_to_swait_exclusive(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_exclusive);
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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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unsigned long flags;
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long ret = 0;
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raw_spin_lock_irqsave(&q->lock, flags);
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if (signal_pending_state(state, current)) {
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/*
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* See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
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* must not see us.
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*/
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list_del_init(&wait->task_list);
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ret = -ERESTARTSYS;
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} else {
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__prepare_to_swait(q, wait);
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set_current_state(state);
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}
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raw_spin_unlock_irqrestore(&q->lock, flags);
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return ret;
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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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