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 #ifdef ANDROID
44 /* On Android, rely on the system's libsync instead of rolling our own
45 * sync_wait() and sync_merge(). This gives us compatibility with pre-4.7
46 * Android kernels.
47 */
48 #include <android/sync.h>
49 #else
50
51 #ifndef SYNC_IOC_MERGE
52 /* duplicated from linux/sync_file.h to avoid build-time dependency
53 * on new (v4.7) kernel headers. Once distro's are mostly using
54 * something newer than v4.7 drop this and #include <linux/sync_file.h>
55 * instead.
56 */
57 struct sync_merge_data {
58 char name[32];
59 int32_t fd2;
60 int32_t fence;
61 uint32_t flags;
62 uint32_t pad;
63 };
64 #define SYNC_IOC_MAGIC '>'
65 #define SYNC_IOC_MERGE _IOWR(SYNC_IOC_MAGIC, 3, struct sync_merge_data)
66 #endif
67
68
69 static inline int sync_wait(int fd, int timeout)
70 {
71 struct pollfd fds = {0};
72 int ret;
73
74 fds.fd = fd;
75 fds.events = POLLIN;
76
77 do {
78 ret = poll(&fds, 1, timeout);
79 if (ret > 0) {
80 if (fds.revents & (POLLERR | POLLNVAL)) {
81 errno = EINVAL;
82 return -1;
83 }
84 return 0;
85 } else if (ret == 0) {
86 errno = ETIME;
87 return -1;
88 }
89 } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
90
91 return ret;
92 }
93
94 static inline int sync_merge(const char *name, int fd1, int fd2)
95 {
96 struct sync_merge_data data = {0};
97 int ret;
98
99 data.fd2 = fd2;
100 strncpy(data.name, name, sizeof(data.name));
101
102 do {
103 ret = ioctl(fd1, SYNC_IOC_MERGE, &data);
104 } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
105
106 if (ret < 0)
107 return ret;
108
109 return data.fence;
110 }
111
112 #endif /* !ANDROID */
113
114 /* accumulate fd2 into fd1. If *fd1 is not a valid fd then dup fd2,
115 * otherwise sync_merge() and close the old *fd1. This can be used
116 * to implement the pattern:
117 *
118 * init()
119 * {
120 * batch.fence_fd = -1;
121 * }
122 *
123 * // does *NOT* take ownership of fd
124 * server_sync(int fd)
125 * {
126 * if (sync_accumulate("foo", &batch.fence_fd, fd)) {
127 * ... error ...
128 * }
129 * }
130 */
sync_accumulate(const char * name,int * fd1,int fd2)131 static inline int sync_accumulate(const char *name, int *fd1, int fd2)
132 {
133 int ret;
134
135 assert(fd2 >= 0);
136
137 if (*fd1 < 0) {
138 *fd1 = dup(fd2);
139 return 0;
140 }
141
142 ret = sync_merge(name, *fd1, fd2);
143 if (ret < 0) {
144 /* leave *fd1 as it is */
145 return ret;
146 }
147
148 close(*fd1);
149 *fd1 = ret;
150
151 return 0;
152 }
153
154 #if defined(__cplusplus)
155 }
156 #endif
157
158 #endif
159