junction/striped/ManualResetEvent.h

   1 /*------------------------------------------------------------------------
   2   Junction: Concurrent data structures in C++
   3   Copyright (c) 2016 Jeff Preshing
   4
   5   Distributed under the Simplified BSD License.
   6   Original location: https://github.com/preshing/junction
   7
   8   This software is distributed WITHOUT ANY WARRANTY; without even the
   9   implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  10   See the LICENSE file for more information.
  11 ------------------------------------------------------------------------*/
  12
  13 #ifndef JUNCTION_STRIPED_MANUALRESETEVENT_H
  14 #define JUNCTION_STRIPED_MANUALRESETEVENT_H
  15
  16 #include <junction/Core.h>
  17
  18 #if JUNCTION_USE_STRIPING
  19
  20 //-----------------------------------
  21 // Striping enabled
  22 //-----------------------------------
  23 #include <junction/striped/ConditionBank.h>
  24
  25 namespace junction {
  26 namespace striped {
  27
  28 class ManualResetEvent {
  29 private:
  30     JUNCTION_STRIPED_CONDITIONBANK_DEFINE_MEMBER()
  31     static const u8 Signaled = 1;
  32     static const u8 HasWaiters = 2;
  33     turf::Atomic<u8> m_state;
  34
  35 public:
  36     ManualResetEvent(bool initialState = false) : m_state(initialState ? Signaled : 0) {
  37     }
  38
  39     ~ManualResetEvent() {
  40     }
  41
  42     void signal() {
  43         u8 prevState = m_state.fetchOr(Signaled, turf::Release);    // Synchronizes-with the load in wait (fast path)
  44         if (prevState & HasWaiters) {
  45             ConditionPair& pair = JUNCTION_STRIPED_CONDITIONBANK_GET(this);
  46             turf::LockGuard<turf::Mutex> guard(pair.mutex);   // Prevents the wake from occuring in the middle of wait()'s critical section
  47             pair.condVar.wakeAll();
  48         }
  49     }
  50
  51     bool isSignaled() const {
  52         return m_state.load(turf::Relaxed) & Signaled;
  53     }
  54
  55     void reset() {
  56         TURF_ASSERT(0); // FIXME: implement it
  57     }
  58
  59     void wait() {
  60         u8 state = m_state.load(turf::Acquire);     // Synchronizes-with the fetchOr in signal (fast path)
  61         if ((state & Signaled) == 0) {
  62             ConditionPair& pair = JUNCTION_STRIPED_CONDITIONBANK_GET(this);
  63             turf::LockGuard<turf::Mutex> guard(pair.mutex);
  64             for (;;) {
  65                 // FIXME: Implement reusable AdaptiveBackoff class and apply it here
  66                 state = m_state.load(turf::Relaxed);
  67                 if (state & Signaled)
  68                     break;
  69                 if (state != HasWaiters) {
  70                     TURF_ASSERT(state == 0);
  71                     if (!m_state.compareExchangeWeak(state, HasWaiters, turf::Relaxed, turf::Relaxed))
  72                         continue;
  73                 }
  74                 // The lock ensures signal can't wakeAll between the load and the wait
  75                 pair.condVar.wait(guard);
  76             }
  77         }
  78     }
  79 };
  80
  81 } // namespace striped
  82 } // namespace junction
  83
  84 #else // JUNCTION_USE_STRIPING
  85
  86 //-----------------------------------
  87 // Striping disabled
  88 //-----------------------------------
  89 #include <turf/ManualResetEvent.h>
  90
  91 namespace junction {
  92 namespace striped {
  93 typedef turf::ManualResetEvent ManualResetEvent;
  94 } // namespace striped
  95 } // namespace junction
  96
  97 #endif // JUNCTION_USE_STRIPING
  98
  99 #endif // JUNCTION_STRIPED_MANUALRESETEVENT_H