src/core/lib/iomgr/wakeup_fd_eventfd.c

/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include "src/core/lib/iomgr/port.h"

#ifdef GRPC_LINUX_EVENTFD

#include <errno.h>
#include <sys/eventfd.h>
#include <unistd.h>

#include <grpc/support/log.h>

#include "src/core/lib/iomgr/wakeup_fd_posix.h"
#include "src/core/lib/profiling/timers.h"

static grpc_error* eventfd_create(grpc_wakeup_fd* fd_info) {
  int efd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
  if (efd < 0) {
    return GRPC_OS_ERROR(errno, "eventfd");
  }
  fd_info->read_fd = efd;
  fd_info->write_fd = -1;
  return GRPC_ERROR_NONE;
}

static grpc_error* eventfd_consume(grpc_wakeup_fd* fd_info) {
  eventfd_t value;
  int err;
  do {
    err = eventfd_read(fd_info->read_fd, &value);
  } while (err < 0 && errno == EINTR);
  if (err < 0 && errno != EAGAIN) {
    return GRPC_OS_ERROR(errno, "eventfd_read");
  }
  return GRPC_ERROR_NONE;
}

static grpc_error* eventfd_wakeup(grpc_wakeup_fd* fd_info) {
  int err;
  GPR_TIMER_BEGIN("eventfd_wakeup", 0);
  do {
    err = eventfd_write(fd_info->read_fd, 1);
  } while (err < 0 && errno == EINTR);
  if (err < 0) {
    return GRPC_OS_ERROR(errno, "eventfd_write");
  }
  GPR_TIMER_END("eventfd_wakeup", 0);
  return GRPC_ERROR_NONE;
}

static void eventfd_destroy(grpc_wakeup_fd* fd_info) {
  if (fd_info->read_fd != 0) close(fd_info->read_fd);
}

static int eventfd_check_availability(void) {
  const int efd = eventfd(0, 0);
  const int is_available = efd >= 0;
  if (is_available) close(efd);
  return is_available;
}

const grpc_wakeup_fd_vtable grpc_specialized_wakeup_fd_vtable = {
    eventfd_create, eventfd_consume, eventfd_wakeup, eventfd_destroy,
    eventfd_check_availability};

#endif /* GRPC_LINUX_EVENTFD */