futex.cc

   1 // futex -*- C++ -*-
   2
   3 // Copyright (C) 2015-2019 Free Software Foundation, Inc.
   4 //
   5 // This is a reimplementation of libstdc++-v3/src/c++11/futex.cc.
   6
   7 #include <bits/atomic_futex.h>
   8 #ifdef _GLIBCXX_HAS_GTHREADS
   9 #if defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1
  10 #include <chrono>
  11 #include <climits>
  12 #include <syscall.h>
  13 #include <unistd.h>
  14 #include <sys/time.h>
  15 #include <errno.h>
  16 #include <debug/debug.h>
  17
  18 #include "model.h"
  19 #include "execution.h"
  20 #include "mutex.h"
  21 #include <condition_variable>
  22
  23 // Constants for the wait/wake futex syscall operations
  24 const unsigned futex_wait_op = 0;
  25 const unsigned futex_wake_op = 1;
  26
  27 namespace std _GLIBCXX_VISIBILITY(default)
  28 {
  29         _GLIBCXX_BEGIN_NAMESPACE_VERSION
  30
  31         bool
  32         __atomic_futex_unsigned_base::_M_futex_wait_until(unsigned *__addr,
  33                                                                                                                                                                                                                 unsigned __val,
  34                                                                                                                                                                                                                 bool __has_timeout, chrono::seconds __s, chrono::nanoseconds __ns)
  35         {
  36                 // do nothing if the two values are not equal
  37                 if ( *__addr != __val ) {
  38                         return true;
  39                 }
  40
  41                 // if a timeout is specified, return immedialy. Letting the scheduler decide how long this thread will wait.
  42                 if (__has_timeout) {
  43                         return true;
  44                 }
  45
  46                 ModelExecution *execution = model->get_execution();
  47
  48                 cdsc::snapcondition_variable *v = new cdsc::snapcondition_variable();
  49                 cdsc::snapmutex *m = new cdsc::snapmutex();
  50
  51                 execution->getCondMap()->put( (pthread_cond_t *) __addr, v);
  52                 execution->getMutexMap()->put( (pthread_mutex_t *) __addr, m);
  53
  54                 v->wait(*m);
  55                 return true;
  56         }
  57
  58         void
  59         __atomic_futex_unsigned_base::_M_futex_notify_all(unsigned* __addr)
  60         {
  61                 // INT_MAX wakes all the waiters at the address __addr
  62                 ModelExecution *execution = model->get_execution();
  63                 cdsc::condition_variable *v = execution->getCondMap()->get( (pthread_cond_t *) __addr);
  64
  65                 if (v == NULL)
  66                         return;// do nothing
  67
  68                 v->notify_all();
  69         }
  70
  71         _GLIBCXX_END_NAMESPACE_VERSION
  72 }
  73 #endif  // defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1
  74 #endif  // _GLIBCXX_HAS_GTHREADS