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wakeup_fd_posix.h
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1 /*
2 *
3 * Copyright 2015, Google Inc.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met:
9 *
10 * * Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * * Redistributions in binary form must reproduce the above
13 * copyright notice, this list of conditions and the following disclaimer
14 * in the documentation and/or other materials provided with the
15 * distribution.
16 * * Neither the name of Google Inc. nor the names of its
17 * contributors may be used to endorse or promote products derived from
18 * this software without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 *
32 */
33
34 /*
35 * wakeup_fd abstracts the concept of a file descriptor for the purpose of
36 * waking up a thread in select()/poll()/epoll_wait()/etc.
37
38 * The poll() family of system calls provide a way for a thread to block until
39 * there is activity on one (or more) of a set of file descriptors. An
40 * application may wish to wake up this thread to do non file related work. The
41 * typical way to do this is to add a pipe to the set of file descriptors, then
42 * write to the pipe to wake up the thread in poll().
43 *
44 * Linux has a lighter weight eventfd specifically designed for this purpose.
45 * wakeup_fd abstracts the difference between the two.
46 *
47 * Setup:
48 * 1. Before calling anything, call global_init() at least once.
49 * 1. Call grpc_wakeup_fd_create() to get a wakeup_fd.
50 * 2. Add the result of GRPC_WAKEUP_FD_FD to the set of monitored file
51 * descriptors for the poll() style API you are using. Monitor the file
52 * descriptor for readability.
53 * 3. To tear down, call grpc_wakeup_fd_destroy(). This closes the underlying
54 * file descriptor.
55 *
56 * Usage:
57 * 1. To wake up a polling thread, call grpc_wakeup_fd_wakeup() on a wakeup_fd
58 * it is monitoring.
59 * 2. If the polling thread was awakened by a wakeup_fd event, call
60 * grpc_wakeup_fd_consume_wakeup() on it.
61 */
62 #ifndef GRPC_INTERNAL_CORE_IOMGR_WAKEUP_FD_POSIX_H
63 #define GRPC_INTERNAL_CORE_IOMGR_WAKEUP_FD_POSIX_H
64
65 void grpc_wakeup_fd_global_init(void);
66 void grpc_wakeup_fd_global_destroy(void);
67
68 /* Force using the fallback implementation. This is intended for testing
69 * purposes only.*/
70 void grpc_wakeup_fd_global_init_force_fallback(void);
71
72 typedef struct grpc_wakeup_fd_info grpc_wakeup_fd_info;
73
74 typedef struct grpc_wakeup_fd_vtable {
75 void (*create)(grpc_wakeup_fd_info *fd_info);
76 void (*consume)(grpc_wakeup_fd_info *fd_info);
77 void (*wakeup)(grpc_wakeup_fd_info *fd_info);
78 void (*destroy)(grpc_wakeup_fd_info *fd_info);
79 /* Must be called before calling any other functions */
80 int (*check_availability)(void);
81 } grpc_wakeup_fd_vtable;
82
83 struct grpc_wakeup_fd_info {
84 int read_fd;
85 int write_fd;
86 };
87
88 #define GRPC_WAKEUP_FD_GET_READ_FD(fd_info) ((fd_info)->read_fd)
89
90 void grpc_wakeup_fd_create(grpc_wakeup_fd_info *fd_info);
91 void grpc_wakeup_fd_consume_wakeup(grpc_wakeup_fd_info *fd_info);
92 void grpc_wakeup_fd_wakeup(grpc_wakeup_fd_info *fd_info);
93 void grpc_wakeup_fd_destroy(grpc_wakeup_fd_info *fd_info);
94
95 /* Defined in some specialized implementation's .c file, or by
96 * wakeup_fd_nospecial.c if no such implementation exists. */
97 extern const grpc_wakeup_fd_vtable grpc_specialized_wakeup_fd_vtable;
98
99 #endif /* GRPC_INTERNAL_CORE_IOMGR_WAKEUP_FD_POSIX_H */
grpc_wakeup_fd_create
void grpc_wakeup_fd_create(grpc_wakeup_fd_info *fd_info)
grpc_wakeup_fd_vtable::create
void(* create)(grpc_wakeup_fd_info *fd_info)
Definition: wakeup_fd_posix.h:75
grpc_wakeup_fd_vtable::check_availability
int(* check_availability)(void)
Definition: wakeup_fd_posix.h:80
grpc_wakeup_fd_wakeup
void grpc_wakeup_fd_wakeup(grpc_wakeup_fd_info *fd_info)
grpc_wakeup_fd_info
Definition: wakeup_fd_posix.h:83
grpc_wakeup_fd_global_init_force_fallback
void grpc_wakeup_fd_global_init_force_fallback(void)
grpc_wakeup_fd_consume_wakeup
void grpc_wakeup_fd_consume_wakeup(grpc_wakeup_fd_info *fd_info)
grpc_wakeup_fd_vtable::consume
void(* consume)(grpc_wakeup_fd_info *fd_info)
Definition: wakeup_fd_posix.h:76
grpc_wakeup_fd_info::write_fd
int write_fd
Definition: wakeup_fd_posix.h:85
grpc_wakeup_fd_vtable::destroy
void(* destroy)(grpc_wakeup_fd_info *fd_info)
Definition: wakeup_fd_posix.h:78
grpc_wakeup_fd_global_init
void grpc_wakeup_fd_global_init(void)
grpc_specialized_wakeup_fd_vtable
const grpc_wakeup_fd_vtable grpc_specialized_wakeup_fd_vtable
grpc_wakeup_fd_vtable
struct grpc_wakeup_fd_vtable grpc_wakeup_fd_vtable
grpc_wakeup_fd_global_destroy
void grpc_wakeup_fd_global_destroy(void)
grpc_wakeup_fd_vtable::wakeup
void(* wakeup)(grpc_wakeup_fd_info *fd_info)
Definition: wakeup_fd_posix.h:77
grpc_wakeup_fd_vtable
Definition: wakeup_fd_posix.h:74
grpc_wakeup_fd_destroy
void grpc_wakeup_fd_destroy(grpc_wakeup_fd_info *fd_info)
grpc_wakeup_fd_info::read_fd
int read_fd
Definition: wakeup_fd_posix.h:84