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 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 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 */ 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
