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
  31         /* "Not copyable" and "not moveable" Mutex requirements. */
  32         read_lock(read_lock const &) = delete;
  33         read_lock &operator=(read_lock const &) = delete;
  34
  35         void lock()
  36         {
  37                 rcu_read_lock();
  38         }
  39
  40         bool try_lock()
  41         {
  42                 lock();
  43                 return true;
  44         }
  45
  46         void unlock()
  47         {
  48                 rcu_read_unlock();
  49         }
  50 };
  51 } /* namespace details */
  52
  53 /*
  54  * Provides the basic concept of std::lock_guard for rcu reader locks.
  55  *
  56  * The RCU reader lock is held for the duration of lock_guard's lifetime.
  57  */
  58 class read_lock_guard {
  59 public:
  60         read_lock_guard() : _guard(_lock)
  61         {
  62         }
  63
  64         read_lock_guard(const read_lock_guard &) = delete;
  65
  66 private:
  67         details::read_lock _lock;
  68         std::lock_guard<details::read_lock> _guard;
  69 };
  70
  71 using unique_read_lock = std::unique_lock<details::read_lock>;
  72
  73 } /* namespace urcu */
  74 } /* namespace lttng */
  75
  76 #endif /* LTTNG_URCU_H */