src/common/eventfd.hpp

   1 /*
   2  * Copyright (C) 2023 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #ifndef LTTNG_EVENTFD_HPP
   9 #define LTTNG_EVENTFD_HPP
  10
  11 #include <common/file-descriptor.hpp>
  12
  13 #include <cstdint>
  14
  15 namespace lttng {
  16
  17 class eventfd : public file_descriptor {
  18 public:
  19         /* Throws a posix_error exception on failure to create the underlying resource. */
  20         explicit eventfd(bool use_semaphore_semantics = true, std::uint64_t initial_value = 0);
  21         eventfd(const eventfd&) = delete;
  22         eventfd& operator=(const eventfd&) = delete;
  23         eventfd(eventfd&&) = delete;
  24         void operator=(eventfd&&) = delete;
  25         ~eventfd() = default;
  26
  27         /* Throws on error. */
  28         void increment(std::uint64_t value = 1);
  29         /*
  30          * Note that decrement() will block if the underlying value of the eventfd is 0 when
  31          * semaphore semantics are used, see EVENTFD(2).
  32          *
  33          * decrement() returns the new value of the underlying counter of the eventfd.
  34          *
  35          * Throws on error.
  36          */
  37         std::uint64_t decrement();
  38 };
  39
  40 } /* namespace lttng */
  41
  42 #endif /* LTTNG_EVENTFD_HPP */