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