ceph/src/boost/libs/atomic/src/lockpool.cpp

   1 /*
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * Copyright (c) 2011 Helge Bahmann
   7  * Copyright (c) 2013-2014 Andrey Semashev
   8  */
   9 /*!
  10  * \file   lockpool.cpp
  11  *
  12  * This file contains implementation of the lockpool used to emulate atomic ops.
  13  */
  14
  15 #include <cstddef>
  16 #include <boost/config.hpp>
  17 #include <boost/assert.hpp>
  18 #include <boost/memory_order.hpp>
  19 #include <boost/atomic/capabilities.hpp>
  20
  21 #if BOOST_ATOMIC_FLAG_LOCK_FREE == 2
  22 #include <boost/atomic/detail/operations_lockfree.hpp>
  23 #elif !defined(BOOST_HAS_PTHREADS)
  24 #error Boost.Atomic: Unsupported target platform, POSIX threads are required when native atomic operations are not available
  25 #else
  26 #include <pthread.h>
  27 #define BOOST_ATOMIC_USE_PTHREAD
  28 #endif
  29
  30 #include <boost/atomic/detail/lockpool.hpp>
  31 #include <boost/atomic/detail/pause.hpp>
  32
  33 namespace boost {
  34 namespace atomics {
  35 namespace detail {
  36
  37 namespace {
  38
  39 // This seems to be the maximum across all modern CPUs
  40 // NOTE: This constant is made as a macro because some compilers (gcc 4.4 for one) don't allow enums or namespace scope constants in alignment attributes
  41 #define BOOST_ATOMIC_CACHE_LINE_SIZE 64
  42
  43 #if defined(BOOST_ATOMIC_USE_PTHREAD)
  44 typedef pthread_mutex_t lock_type;
  45 #else
  46 typedef atomics::detail::operations< 1u, false > lock_operations;
  47 typedef lock_operations::storage_type lock_type;
  48 #endif
  49
  50 enum
  51 {
  52     padding_size = (sizeof(lock_type) <= BOOST_ATOMIC_CACHE_LINE_SIZE ?
  53         (BOOST_ATOMIC_CACHE_LINE_SIZE - sizeof(lock_type)) :
  54         (BOOST_ATOMIC_CACHE_LINE_SIZE - sizeof(lock_type) % BOOST_ATOMIC_CACHE_LINE_SIZE))
  55 };
  56
  57 template< unsigned int PaddingSize >
  58 struct BOOST_ALIGNMENT(BOOST_ATOMIC_CACHE_LINE_SIZE) padded_lock
  59 {
  60     lock_type lock;
  61     // The additional padding is needed to avoid false sharing between locks
  62     char padding[PaddingSize];
  63 };
  64
  65 template< >
  66 struct BOOST_ALIGNMENT(BOOST_ATOMIC_CACHE_LINE_SIZE) padded_lock< 0u >
  67 {
  68     lock_type lock;
  69 };
  70
  71 typedef padded_lock< padding_size > padded_lock_t;
  72
  73 static padded_lock_t g_lock_pool[41]
  74 #if defined(BOOST_ATOMIC_USE_PTHREAD)
  75 =
  76 {
  77     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  78     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  79     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  80     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  81     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  82     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  83     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  84     { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER }, { PTHREAD_MUTEX_INITIALIZER },
  85     { PTHREAD_MUTEX_INITIALIZER }
  86 }
  87 #endif
  88 ;
  89
  90 } // namespace
  91
  92
  93 #if !defined(BOOST_ATOMIC_USE_PTHREAD)
  94
  95 // NOTE: This function must NOT be inline. Otherwise MSVC 9 will sometimes generate broken code for modulus operation which result in crashes.
  96 BOOST_ATOMIC_DECL lockpool::scoped_lock::scoped_lock(const volatile void* addr) BOOST_NOEXCEPT :
  97     m_lock(&g_lock_pool[reinterpret_cast< std::size_t >(addr) % (sizeof(g_lock_pool) / sizeof(*g_lock_pool))].lock)
  98 {
  99     while (lock_operations::test_and_set(*static_cast< lock_type* >(m_lock), memory_order_acquire))
 100     {
 101         do
 102         {
 103             atomics::detail::pause();
 104         }
 105         while (!!lock_operations::load(*static_cast< lock_type* >(m_lock), memory_order_relaxed));
 106     }
 107 }
 108
 109 BOOST_ATOMIC_DECL lockpool::scoped_lock::~scoped_lock() BOOST_NOEXCEPT
 110 {
 111     lock_operations::clear(*static_cast< lock_type* >(m_lock), memory_order_release);
 112 }
 113
 114 BOOST_ATOMIC_DECL void signal_fence() BOOST_NOEXCEPT;
 115
 116 #else // !defined(BOOST_ATOMIC_USE_PTHREAD)
 117
 118 BOOST_ATOMIC_DECL lockpool::scoped_lock::scoped_lock(const volatile void* addr) BOOST_NOEXCEPT :
 119     m_lock(&g_lock_pool[reinterpret_cast< std::size_t >(addr) % (sizeof(g_lock_pool) / sizeof(*g_lock_pool))].lock)
 120 {
 121     BOOST_VERIFY(pthread_mutex_lock(static_cast< pthread_mutex_t* >(m_lock)) == 0);
 122 }
 123
 124 BOOST_ATOMIC_DECL lockpool::scoped_lock::~scoped_lock() BOOST_NOEXCEPT
 125 {
 126     BOOST_VERIFY(pthread_mutex_unlock(static_cast< pthread_mutex_t* >(m_lock)) == 0);
 127 }
 128
 129 #endif // !defined(BOOST_ATOMIC_USE_PTHREAD)
 130
 131 BOOST_ATOMIC_DECL void lockpool::thread_fence() BOOST_NOEXCEPT
 132 {
 133 #if BOOST_ATOMIC_THREAD_FENCE > 0
 134     atomics::detail::thread_fence(memory_order_seq_cst);
 135 #else
 136     // Emulate full fence by locking/unlocking a mutex
 137     scoped_lock lock(0);
 138 #endif
 139 }
 140
 141 BOOST_ATOMIC_DECL void lockpool::signal_fence() BOOST_NOEXCEPT
 142 {
 143     // This function is intentionally non-inline, even if empty. This forces the compiler to treat its call as a compiler barrier.
 144 #if BOOST_ATOMIC_SIGNAL_FENCE > 0
 145     atomics::detail::signal_fence(memory_order_seq_cst);
 146 #endif
 147 }
 148
 149 } // namespace detail
 150 } // namespace atomics
 151 } // namespace boost