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Release 4.12 include/linux/rcuwait.h

Directory: include/linux
#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; where it is forbidden to use
 * after exit_notify(). task_struct is not properly rcu protected,
 * unless dealing with rcu-aware lists, ie: find_task_by_*().
 *
 * Alternatively we have task_rcu_dereference(), but the return
 * semantics have different implications which would break the
 * wakeup side. 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 *task;
};


#define __RCUWAIT_INITIALIZER(name)		\
	{ .task = NULL, }


static inline void rcuwait_init(struct rcuwait *w) { w->task = NULL; }

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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) \ ({ \ /* \ * Complain if we are called after do_exit()/exit_notify(), \ * as we cannot rely on the rcu critical region for the \ * wakeup side. \ */ \ WARN_ON(current->exit_state); \ \ 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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Directory: include/linux
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