1 /*
2 * sync abstraction
3 * Copyright 2015-2016 Collabora Ltd.
4 *
5 * Based on the implementation from the Android Open Source Project,
6 *
7 * Copyright 2012 Google, Inc
8 *
9 * Permission is hereby granted, free of charge, to any person obtaining a
10 * copy of this software and associated documentation files (the "Software"),
11 * to deal in the Software without restriction, including without limitation
12 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13 * and/or sell copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following conditions:
15 *
16 * The above copyright notice and this permission notice shall be included in
17 * all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
22 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
23 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
24 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
25 * OTHER DEALINGS IN THE SOFTWARE.
26 */
27
28 #ifndef _LIBSYNC_H
29 #define _LIBSYNC_H
30
31 #include <assert.h>
32 #include <errno.h>
33 #include <stdint.h>
34 #include <string.h>
35 #include <sys/ioctl.h>
36 #include <sys/poll.h>
37 #include <unistd.h>
38
39 #if defined(__cplusplus)
40 extern "C" {
41 #endif
42
43 #ifndef SYNC_IOC_MERGE
44 /* duplicated from linux/sync_file.h to avoid build-time dependency
45 * on new (v4.7) kernel headers. Once distro's are mostly using
46 * something newer than v4.7 drop this and #include <linux/sync_file.h>
47 * instead.
48 */
49 struct sync_merge_data {
50 char name[32];
51 int32_t fd2;
52 int32_t fence;
53 uint32_t flags;
54 uint32_t pad;
55 };
56 #define SYNC_IOC_MAGIC '>'
57 #define SYNC_IOC_MERGE _IOWR(SYNC_IOC_MAGIC, 3, struct sync_merge_data)
58 #endif
59
60
sync_wait(int fd,int timeout)61 static inline int sync_wait(int fd, int timeout)
62 {
63 struct pollfd fds = {0};
64 int ret;
65
66 fds.fd = fd;
67 fds.events = POLLIN;
68
69 do {
70 ret = poll(&fds, 1, timeout);
71 if (ret > 0) {
72 if (fds.revents & (POLLERR | POLLNVAL)) {
73 errno = EINVAL;
74 return -1;
75 }
76 return 0;
77 } else if (ret == 0) {
78 errno = ETIME;
79 return -1;
80 }
81 } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
82
83 return ret;
84 }
85
sync_merge(const char * name,int fd1,int fd2)86 static inline int sync_merge(const char *name, int fd1, int fd2)
87 {
88 struct sync_merge_data data = {0};
89 int ret;
90
91 data.fd2 = fd2;
92 strncpy(data.name, name, sizeof(data.name));
93
94 do {
95 ret = ioctl(fd1, SYNC_IOC_MERGE, &data);
96 } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
97
98 if (ret < 0)
99 return ret;
100
101 return data.fence;
102 }
103
104 /* accumulate fd2 into fd1. If *fd1 is not a valid fd then dup fd2,
105 * otherwise sync_merge() and close the old *fd1. This can be used
106 * to implement the pattern:
107 *
108 * init()
109 * {
110 * batch.fence_fd = -1;
111 * }
112 *
113 * // does *NOT* take ownership of fd
114 * server_sync(int fd)
115 * {
116 * if (sync_accumulate("foo", &batch.fence_fd, fd)) {
117 * ... error ...
118 * }
119 * }
120 */
sync_accumulate(const char * name,int * fd1,int fd2)121 static inline int sync_accumulate(const char *name, int *fd1, int fd2)
122 {
123 int ret;
124
125 assert(fd2 >= 0);
126
127 if (*fd1 < 0) {
128 *fd1 = dup(fd2);
129 return 0;
130 }
131
132 ret = sync_merge(name, *fd1, fd2);
133 if (ret < 0) {
134 /* leave *fd1 as it is */
135 return ret;
136 }
137
138 close(*fd1);
139 *fd1 = ret;
140
141 return 0;
142 }
143
144 #if defined(__cplusplus)
145 }
146 #endif
147
148 #endif
149