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      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 "bt_osi_semaphore"
     20 
     21 #include "osi/include/semaphore.h"
     22 
     23 #include <base/logging.h>
     24 #include <errno.h>
     25 #include <fcntl.h>
     26 #include <malloc.h>
     27 #include <string.h>
     28 #include <sys/eventfd.h>
     29 #include <unistd.h>
     30 
     31 #include "osi/include/allocator.h"
     32 #include "osi/include/log.h"
     33 #include "osi/include/osi.h"
     34 
     35 #if !defined(EFD_SEMAPHORE)
     36 #define EFD_SEMAPHORE (1 << 0)
     37 #endif
     38 
     39 struct semaphore_t {
     40   int fd;
     41 };
     42 
     43 semaphore_t* semaphore_new(unsigned int value) {
     44   semaphore_t* ret = static_cast<semaphore_t*>(osi_malloc(sizeof(semaphore_t)));
     45   ret->fd = eventfd(value, EFD_SEMAPHORE);
     46   if (ret->fd == INVALID_FD) {
     47     LOG_ERROR(LOG_TAG, "%s unable to allocate semaphore: %s", __func__,
     48               strerror(errno));
     49     osi_free(ret);
     50     ret = NULL;
     51   }
     52   return ret;
     53 }
     54 
     55 void semaphore_free(semaphore_t* semaphore) {
     56   if (!semaphore) return;
     57 
     58   if (semaphore->fd != INVALID_FD) close(semaphore->fd);
     59   osi_free(semaphore);
     60 }
     61 
     62 void semaphore_wait(semaphore_t* semaphore) {
     63   CHECK(semaphore != NULL);
     64   CHECK(semaphore->fd != INVALID_FD);
     65 
     66   eventfd_t value;
     67   if (eventfd_read(semaphore->fd, &value) == -1)
     68     LOG_ERROR(LOG_TAG, "%s unable to wait on semaphore: %s", __func__,
     69               strerror(errno));
     70 }
     71 
     72 bool semaphore_try_wait(semaphore_t* semaphore) {
     73   CHECK(semaphore != NULL);
     74   CHECK(semaphore->fd != INVALID_FD);
     75 
     76   int flags = fcntl(semaphore->fd, F_GETFL);
     77   if (flags == -1) {
     78     LOG_ERROR(LOG_TAG, "%s unable to get flags for semaphore fd: %s", __func__,
     79               strerror(errno));
     80     return false;
     81   }
     82   if (fcntl(semaphore->fd, F_SETFL, flags | O_NONBLOCK) == -1) {
     83     LOG_ERROR(LOG_TAG, "%s unable to set O_NONBLOCK for semaphore fd: %s",
     84               __func__, strerror(errno));
     85     return false;
     86   }
     87 
     88   bool rc = true;
     89   eventfd_t value;
     90   if (eventfd_read(semaphore->fd, &value) == -1) rc = false;
     91 
     92   if (fcntl(semaphore->fd, F_SETFL, flags) == -1)
     93     LOG_ERROR(LOG_TAG, "%s unable to restore flags for semaphore fd: %s",
     94               __func__, strerror(errno));
     95   return rc;
     96 }
     97 
     98 void semaphore_post(semaphore_t* semaphore) {
     99   CHECK(semaphore != NULL);
    100   CHECK(semaphore->fd != INVALID_FD);
    101 
    102   if (eventfd_write(semaphore->fd, 1ULL) == -1)
    103     LOG_ERROR(LOG_TAG, "%s unable to post to semaphore: %s", __func__,
    104               strerror(errno));
    105 }
    106 
    107 int semaphore_get_fd(const semaphore_t* semaphore) {
    108   CHECK(semaphore != NULL);
    109   CHECK(semaphore->fd != INVALID_FD);
    110   return semaphore->fd;
    111 }
    112