1 /****************************************************************************** 2 * 3 * Copyright (C) 2014 Google, Inc. 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at: 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 ******************************************************************************/ 18 19 #define LOG_TAG "osi_semaphore" 20 21 #include <assert.h> 22 #include <errno.h> 23 #include <fcntl.h> 24 #include <string.h> 25 #include <sys/eventfd.h> 26 #include <utils/Log.h> 27 28 #include "semaphore.h" 29 30 #if !defined(EFD_SEMAPHORE) 31 # define EFD_SEMAPHORE (1 << 0) 32 #endif 33 34 struct semaphore_t { 35 int fd; 36 }; 37 38 semaphore_t *semaphore_new(unsigned int value) { 39 semaphore_t *ret = malloc(sizeof(semaphore_t)); 40 if (ret) { 41 ret->fd = eventfd(value, EFD_SEMAPHORE); 42 if (ret->fd == -1) { 43 ALOGE("%s unable to allocate semaphore: %s", __func__, strerror(errno)); 44 free(ret); 45 ret = NULL; 46 } 47 } 48 return ret; 49 } 50 51 void semaphore_free(semaphore_t *semaphore) { 52 if (semaphore->fd != -1) 53 close(semaphore->fd); 54 free(semaphore); 55 } 56 57 void semaphore_wait(semaphore_t *semaphore) { 58 assert(semaphore != NULL); 59 assert(semaphore->fd != -1); 60 61 uint64_t value; 62 if (eventfd_read(semaphore->fd, &value) == -1) 63 ALOGE("%s unable to wait on semaphore: %s", __func__, strerror(errno)); 64 } 65 66 bool semaphore_try_wait(semaphore_t *semaphore) { 67 assert(semaphore != NULL); 68 assert(semaphore->fd != -1); 69 70 int flags = fcntl(semaphore->fd, F_GETFL); 71 if (flags == -1) { 72 ALOGE("%s unable to get flags for semaphore fd: %s", __func__, strerror(errno)); 73 return false; 74 } 75 if (fcntl(semaphore->fd, F_SETFL, flags | O_NONBLOCK) == -1) { 76 ALOGE("%s unable to set O_NONBLOCK for semaphore fd: %s", __func__, strerror(errno)); 77 return false; 78 } 79 80 eventfd_t value; 81 if (eventfd_read(semaphore->fd, &value) == -1) 82 return false; 83 84 if (fcntl(semaphore->fd, F_SETFL, flags) == -1) 85 ALOGE("%s unable to resetore flags for semaphore fd: %s", __func__, strerror(errno)); 86 return true; 87 } 88 89 void semaphore_post(semaphore_t *semaphore) { 90 assert(semaphore != NULL); 91 assert(semaphore->fd != -1); 92 93 if (eventfd_write(semaphore->fd, 1ULL) == -1) 94 ALOGE("%s unable to post to semaphore: %s", __func__, strerror(errno)); 95 } 96 97 int semaphore_get_fd(const semaphore_t *semaphore) { 98 assert(semaphore != NULL); 99 assert(semaphore->fd != -1); 100 return semaphore->fd; 101 } 102
