libcxx/src/thread.cpp

   1 //===------------------------- thread.cpp----------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include <__thread/poll_with_backoff.h>
  10 #include <__thread/timed_backoff_policy.h>
  11 #include <exception>
  12 #include <future>
  13 #include <limits>
  14 #include <thread>
  15 #include <vector>
  16
  17 #if __has_include(<unistd.h>)
  18 #  include <unistd.h> // for sysconf
  19 #endif
  20
  21 #if defined(__NetBSD__)
  22 #  pragma weak pthread_create // Do not create libpthread dependency
  23 #endif
  24
  25 #if defined(_LIBCPP_WIN32API)
  26 #  include <windows.h>
  27 #endif
  28
  29 #if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
  30 #  pragma comment(lib, "pthread")
  31 #endif
  32
  33 _LIBCPP_BEGIN_NAMESPACE_STD
  34
  35 thread::~thread() {
  36   if (!__libcpp_thread_isnull(&__t_))
  37     terminate();
  38 }
  39
  40 void thread::join() {
  41   int ec = EINVAL;
  42   if (!__libcpp_thread_isnull(&__t_)) {
  43     ec = __libcpp_thread_join(&__t_);
  44     if (ec == 0)
  45       __t_ = _LIBCPP_NULL_THREAD;
  46   }
  47
  48   if (ec)
  49     __throw_system_error(ec, "thread::join failed");
  50 }
  51
  52 void thread::detach() {
  53   int ec = EINVAL;
  54   if (!__libcpp_thread_isnull(&__t_)) {
  55     ec = __libcpp_thread_detach(&__t_);
  56     if (ec == 0)
  57       __t_ = _LIBCPP_NULL_THREAD;
  58   }
  59
  60   if (ec)
  61     __throw_system_error(ec, "thread::detach failed");
  62 }
  63
  64 unsigned thread::hardware_concurrency() noexcept {
  65 #if defined(_SC_NPROCESSORS_ONLN)
  66   long result = sysconf(_SC_NPROCESSORS_ONLN);
  67   // sysconf returns -1 if the name is invalid, the option does not exist or
  68   // does not have a definite limit.
  69   // if sysconf returns some other negative number, we have no idea
  70   // what is going on. Default to something safe.
  71   if (result < 0)
  72     return 0;
  73   return static_cast<unsigned>(result);
  74 #elif defined(_LIBCPP_WIN32API)
  75   SYSTEM_INFO info;
  76   GetSystemInfo(&info);
  77   return info.dwNumberOfProcessors;
  78 #else // defined(CTL_HW) && defined(HW_NCPU)
  79   // TODO: grovel through /proc or check cpuid on x86 and similar
  80   // instructions on other architectures.
  81 #  if defined(_LIBCPP_WARNING)
  82   _LIBCPP_WARNING("hardware_concurrency not yet implemented")
  83 #  else
  84 #    warning hardware_concurrency not yet implemented
  85 #  endif
  86   return 0; // Means not computable [thread.thread.static]
  87 #endif // defined(CTL_HW) && defined(HW_NCPU)
  88 }
  89
  90 namespace this_thread {
  91
  92 void sleep_for(const chrono::nanoseconds& ns) {
  93   if (ns > chrono::nanoseconds::zero()) {
  94     __libcpp_thread_sleep_for(ns);
  95   }
  96 }
  97
  98 } // namespace this_thread
  99
 100 __thread_specific_ptr<__thread_struct>& __thread_local_data() {
 101   // Even though __thread_specific_ptr's destructor doesn't actually destroy
 102   // anything (see comments there), we can't call it at all because threads may
 103   // outlive the static variable and calling its destructor means accessing an
 104   // object outside of its lifetime, which is UB.
 105   alignas(__thread_specific_ptr<__thread_struct>) static char __b[sizeof(__thread_specific_ptr<__thread_struct>)];
 106   static __thread_specific_ptr<__thread_struct>* __p = new (__b) __thread_specific_ptr<__thread_struct>();
 107   return *__p;
 108 }
 109
 110 // __thread_struct_imp
 111
 112 template <class T>
 113 class _LIBCPP_HIDDEN __hidden_allocator {
 114 public:
 115   typedef T value_type;
 116
 117   T* allocate(size_t __n) { return static_cast<T*>(::operator new(__n * sizeof(T))); }
 118   void deallocate(T* __p, size_t) { ::operator delete(static_cast<void*>(__p)); }
 119
 120   size_t max_size() const { return size_t(~0) / sizeof(T); }
 121 };
 122
 123 class _LIBCPP_HIDDEN __thread_struct_imp {
 124   typedef vector<__assoc_sub_state*, __hidden_allocator<__assoc_sub_state*> > _AsyncStates;
 125   typedef vector<pair<condition_variable*, mutex*>, __hidden_allocator<pair<condition_variable*, mutex*> > > _Notify;
 126
 127   _AsyncStates async_states_;
 128   _Notify notify_;
 129
 130   __thread_struct_imp(const __thread_struct_imp&);
 131   __thread_struct_imp& operator=(const __thread_struct_imp&);
 132
 133 public:
 134   __thread_struct_imp() {}
 135   ~__thread_struct_imp();
 136
 137   void notify_all_at_thread_exit(condition_variable* cv, mutex* m);
 138   void __make_ready_at_thread_exit(__assoc_sub_state* __s);
 139 };
 140
 141 __thread_struct_imp::~__thread_struct_imp() {
 142   for (_Notify::iterator i = notify_.begin(), e = notify_.end(); i != e; ++i) {
 143     i->first->notify_all();
 144     i->second->unlock();
 145   }
 146   for (_AsyncStates::iterator i = async_states_.begin(), e = async_states_.end(); i != e; ++i) {
 147     (*i)->__make_ready();
 148     (*i)->__release_shared();
 149   }
 150 }
 151
 152 void __thread_struct_imp::notify_all_at_thread_exit(condition_variable* cv, mutex* m) {
 153   notify_.push_back(pair<condition_variable*, mutex*>(cv, m));
 154 }
 155
 156 void __thread_struct_imp::__make_ready_at_thread_exit(__assoc_sub_state* __s) {
 157   async_states_.push_back(__s);
 158   __s->__add_shared();
 159 }
 160
 161 // __thread_struct
 162
 163 __thread_struct::__thread_struct() : __p_(new __thread_struct_imp) {}
 164
 165 __thread_struct::~__thread_struct() { delete __p_; }
 166
 167 void __thread_struct::notify_all_at_thread_exit(condition_variable* cv, mutex* m) {
 168   __p_->notify_all_at_thread_exit(cv, m);
 169 }
 170
 171 void __thread_struct::__make_ready_at_thread_exit(__assoc_sub_state* __s) { __p_->__make_ready_at_thread_exit(__s); }
 172
 173 _LIBCPP_END_NAMESPACE_STD