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(
  47                 pair.mutex); // Prevents the wake from occuring in the middle of wait()'s critical section
  48             pair.condVar.wakeAll();
  49         }
  50     }
  51
  52     bool isSignaled() const {
  53         return m_state.load(turf::Relaxed) & Signaled;
  54     }
  55
  56     void reset() {
  57         TURF_ASSERT(0); // FIXME: implement it
  58     }
  59
  60     void wait() {
  61         u8 state = m_state.load(turf::Acquire); // Synchronizes-with the fetchOr in signal (fast path)
  62         if ((state & Signaled) == 0) {
  63             ConditionPair& pair = JUNCTION_STRIPED_CONDITIONBANK_GET(this);
  64             turf::LockGuard<turf::Mutex> guard(pair.mutex);
  65             for (;;) {
  66                 // FIXME: Implement reusable AdaptiveBackoff class and apply it here
  67                 state = m_state.load(turf::Relaxed);
  68                 if (state & Signaled)
  69                     break;
  70                 if (state != HasWaiters) {
  71                     TURF_ASSERT(state == 0);
  72                     if (!m_state.compareExchangeWeak(state, HasWaiters, turf::Relaxed, turf::Relaxed))
  73                         continue;
  74                 }
  75                 // The lock ensures signal can't wakeAll between the load and the wait
  76                 pair.condVar.wait(guard);
  77             }
  78         }
  79     }
  80 };
  81
  82 } // namespace striped
  83 } // namespace junction
  84
  85 #else // JUNCTION_USE_STRIPING
  86
  87 //-----------------------------------
  88 // Striping disabled
  89 //-----------------------------------
  90 #include <turf/ManualResetEvent.h>
  91
  92 namespace junction {
  93 namespace striped {
  94 typedef turf::ManualResetEvent ManualResetEvent;
  95 } // namespace striped
  96 } // namespace junction
  97
  98 #endif // JUNCTION_USE_STRIPING
  99
 100 #endif // JUNCTION_STRIPED_MANUALRESETEVENT_H