src/common/eventfd.cpp

   1 /*
   2  * Copyright (C) 2023 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #include "eventfd.hpp"
   9
  10 #include <common/exception.hpp>
  11 #include <common/format.hpp>
  12 #include <common/readwrite.hpp>
  13
  14 #include <sys/eventfd.h>
  15
  16 lttng::eventfd::eventfd(bool use_semaphore_semantics, std::uint64_t initial_value) :
  17         file_descriptor([use_semaphore_semantics, initial_value]() {
  18                 int flags = ::EFD_CLOEXEC;
  19
  20                 if (use_semaphore_semantics) {
  21                         flags |= ::EFD_SEMAPHORE;
  22                 }
  23
  24                 const auto raw_fd = ::eventfd(initial_value, flags);
  25                 if (raw_fd < 0) {
  26                         LTTNG_THROW_POSIX("Failed to create eventfd", errno);
  27                 }
  28
  29                 return raw_fd;
  30         }())
  31 {
  32 }
  33
  34 void lttng::eventfd::increment(std::uint64_t value)
  35 {
  36         try {
  37                 write(&value, sizeof(value));
  38         } catch (const std::exception& e) {
  39                 LTTNG_THROW_ERROR(lttng::format("Failed to increment eventfd: {}", e.what()));
  40         }
  41 }
  42
  43 std::uint64_t lttng::eventfd::decrement()
  44 {
  45         std::uint64_t value;
  46
  47         try {
  48                 read(&value, sizeof(value));
  49         } catch (const std::exception& e) {
  50                 LTTNG_THROW_ERROR(lttng::format("Failed to decrement eventfd: {}", e.what()));
  51         }
  52
  53         return value;
  54 }