src/common/urcu.hpp

   1 /*
   2  * Copyright (C) 2022 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #ifndef LTTNG_URCU_H
   9 #define LTTNG_URCU_H
  10
  11 #define _LGPL_SOURCE
  12 #include <urcu.h>
  13 #include <mutex>
  14
  15 namespace lttng {
  16 namespace urcu {
  17
  18 namespace details {
  19 /*
  20  * Wrapper around an urcu read lock which satisfies the 'Mutex' named
  21  * requirements of C++11. Satisfying those requirements facilitates the use of
  22  * standard concurrency support library facilities.
  23  *
  24  * read_lock is under the details namespace since it is unlikely to be used
  25  * directly by exception-safe code. See read_lock_guard.
  26  */
  27 class read_lock {
  28 public:
  29         read_lock() = default;
  30         ~read_lock() = default;
  31
  32         /* "Not copyable" and "not moveable" Mutex requirements. */
  33         read_lock(read_lock const&) = delete;
  34         read_lock(read_lock&&) = delete;
  35         read_lock& operator=(read_lock&&) = delete;
  36         read_lock& operator=(const read_lock&) = delete;
  37
  38         void lock()
  39         {
  40                 rcu_read_lock();
  41         }
  42
  43         bool try_lock()
  44         {
  45                 lock();
  46                 return true;
  47         }
  48
  49         void unlock()
  50         {
  51                 rcu_read_unlock();
  52         }
  53 };
  54 } /* namespace details */
  55
  56 /*
  57  * Provides the basic concept of std::lock_guard for rcu reader locks.
  58  *
  59  * The RCU reader lock is held for the duration of lock_guard's lifetime.
  60  */
  61 class read_lock_guard {
  62 public:
  63         read_lock_guard() = default;
  64         ~read_lock_guard() = default;
  65
  66         read_lock_guard(const read_lock_guard&) = delete;
  67         read_lock_guard(read_lock_guard&&) = delete;
  68         read_lock_guard& operator=(read_lock_guard&&) = delete;
  69         read_lock_guard& operator=(const read_lock_guard&) = delete;
  70
  71 private:
  72         details::read_lock _lock;
  73         std::lock_guard<details::read_lock> _guard{ _lock };
  74 };
  75
  76 using unique_read_lock = std::unique_lock<details::read_lock>;
  77
  78 } /* namespace urcu */
  79 } /* namespace lttng */
  80
  81 #endif /* LTTNG_URCU_H */