1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_RCUWAIT_H_
3 #define _LINUX_RCUWAIT_H_
4
5 #include <linux/rcupdate.h>
6 #include <linux/sched/signal.h>
7
8 /*
9 * rcuwait provides a way of blocking and waking up a single
10 * task in an rcu-safe manner.
11 *
12 * The only time @task is non-nil is when a user is blocked (or
13 * checking if it needs to) on a condition, and reset as soon as we
14 * know that the condition has succeeded and are awoken.
15 */
16 struct rcuwait {
17 struct task_struct __rcu *task;
18 };
19
20 #define __RCUWAIT_INITIALIZER(name) \
21 { .task = NULL, }
22
23 static inline void rcuwait_init(struct rcuwait *w)
24 {
25 w->task = NULL;
26 }
27
28 /*
29 * Note: this provides no serialization and, just as with waitqueues,
30 * requires care to estimate as to whether or not the wait is active.
31 */
32 static inline int rcuwait_active(struct rcuwait *w)
33 {
34 return !!rcu_access_pointer(w->task);
35 }
36
37 extern int rcuwait_wake_up(struct rcuwait *w);
38
39 /*
40 * The caller is responsible for locking around rcuwait_wait_event(),
41 * and [prepare_to/finish]_rcuwait() such that writes to @task are
42 * properly serialized.
43 */
44
45 static inline void prepare_to_rcuwait(struct rcuwait *w)
46 {
47 rcu_assign_pointer(w->task, current);
48 }
49
50 extern void finish_rcuwait(struct rcuwait *w);
51
52 #define ___rcuwait_wait_event(w, condition, state, ret, cmd) \
53 ({ \
54 long __ret = ret; \
55 prepare_to_rcuwait(w); \
56 for (;;) { \
57 /* \
58 * Implicit barrier (A) pairs with (B) in \
59 * rcuwait_wake_up(). \
60 */ \
61 set_current_state(state); \
62 if (condition) \
63 break; \
64 \
65 if (signal_pending_state(state, current)) { \
66 __ret = -EINTR; \
67 break; \
68 } \
69 \
70 cmd; \
71 } \
72 finish_rcuwait(w); \
73 __ret; \
74 })
75
76 #define rcuwait_wait_event(w, condition, state) \
77 ___rcuwait_wait_event(w, condition, state, 0, schedule())
78
79 #define __rcuwait_wait_event_timeout(w, condition, state, timeout) \
80 ___rcuwait_wait_event(w, ___wait_cond_timeout(condition), \
81 state, timeout, \
82 __ret = schedule_timeout(__ret))
83
84 #define rcuwait_wait_event_timeout(w, condition, state, timeout) \
85 ({ \
86 long __ret = timeout; \
87 if (!___wait_cond_timeout(condition)) \
88 __ret = __rcuwait_wait_event_timeout(w, condition, \
89 state, timeout); \
90 __ret; \
91 })
92
93 #endif /* _LINUX_RCUWAIT_H_ */
94
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.