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80 lines
1.8 KiB
80 lines
1.8 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef _LINUX_RCUWAIT_H_ |
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#define _LINUX_RCUWAIT_H_ |
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#include <linux/rcupdate.h> |
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#include <linux/sched/signal.h> |
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/* |
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* rcuwait provides a way of blocking and waking up a single |
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* task in an rcu-safe manner. |
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* |
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* The only time @task is non-nil is when a user is blocked (or |
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* checking if it needs to) on a condition, and reset as soon as we |
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* know that the condition has succeeded and are awoken. |
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*/ |
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struct rcuwait { |
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struct task_struct __rcu *task; |
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}; |
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#define __RCUWAIT_INITIALIZER(name) \ |
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{ .task = NULL, } |
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static inline void rcuwait_init(struct rcuwait *w) |
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{ |
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w->task = NULL; |
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} |
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/* |
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* Note: this provides no serialization and, just as with waitqueues, |
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* requires care to estimate as to whether or not the wait is active. |
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*/ |
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static inline int rcuwait_active(struct rcuwait *w) |
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{ |
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return !!rcu_access_pointer(w->task); |
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} |
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extern int rcuwait_wake_up(struct rcuwait *w); |
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/* |
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* The caller is responsible for locking around rcuwait_wait_event(), |
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* and [prepare_to/finish]_rcuwait() such that writes to @task are |
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* properly serialized. |
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*/ |
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static inline void prepare_to_rcuwait(struct rcuwait *w) |
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{ |
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rcu_assign_pointer(w->task, current); |
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} |
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static inline void finish_rcuwait(struct rcuwait *w) |
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{ |
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rcu_assign_pointer(w->task, NULL); |
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__set_current_state(TASK_RUNNING); |
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} |
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#define rcuwait_wait_event(w, condition, state) \ |
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({ \ |
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int __ret = 0; \ |
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prepare_to_rcuwait(w); \ |
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for (;;) { \ |
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/* \ |
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* Implicit barrier (A) pairs with (B) in \ |
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* rcuwait_wake_up(). \ |
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*/ \ |
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set_current_state(state); \ |
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if (condition) \ |
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break; \ |
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\ |
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if (signal_pending_state(state, current)) { \ |
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__ret = -EINTR; \ |
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break; \ |
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} \ |
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\ |
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schedule(); \ |
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} \ |
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finish_rcuwait(w); \ |
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__ret; \ |
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}) |
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#endif /* _LINUX_RCUWAIT_H_ */
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