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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_RCUWAIT_H_
#define _LINUX_RCUWAIT_H_
#include <linux/rcupdate.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;
}
extern void rcuwait_wake_up(struct rcuwait *w);
/*
* The caller is responsible for locking around rcuwait_wait_event(),
* such that writes to @task are properly serialized.
*/
#define rcuwait_wait_event(w, condition) \
({ \
rcu_assign_pointer((w)->task, current); \
for (;;) { \
/* \
* Implicit barrier (A) pairs with (B) in \
* rcuwait_wake_up(). \
*/ \
set_current_state(TASK_UNINTERRUPTIBLE); \
if (condition) \
break; \
\
schedule(); \
} \
\
WRITE_ONCE((w)->task, NULL); \
__set_current_state(TASK_RUNNING); \
})
#endif /* _LINUX_RCUWAIT_H_ */
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