SST  12.0.1
StructuralSimulationToolkit
sstmutex.h
1 // Copyright 2009-2022 NTESS. Under the terms
2 // of Contract DE-NA0003525 with NTESS, the U.S.
3 // Government retains certain rights in this software.
4 //
5 // Copyright (c) 2009-2022, NTESS
6 // All rights reserved.
7 //
8 // This file is part of the SST software package. For license
9 // information, see the LICENSE file in the top level directory of the
10 // distribution.
11 
12 #ifndef SST_CORE_INTERPROCESS_MUTEX_H
13 #define SST_CORE_INTERPROCESS_MUTEX_H
14 
15 #include <sched.h>
16 #include <time.h>
17 
18 namespace SST {
19 namespace Core {
20 namespace Interprocess {
21 
22 #define SST_CORE_INTERPROCESS_LOCKED 1
23 #define SST_CORE_INTERPROCESS_UNLOCKED 0
24 
25 class SSTMutex
26 {
27 
28 public:
29  SSTMutex() { lockVal = SST_CORE_INTERPROCESS_UNLOCKED; }
30 
31  void processorPause(int currentCount)
32  {
33  if ( currentCount < 64 ) {
34 #if defined(__x86_64__)
35  __asm__ __volatile__("pause" : : : "memory");
36 #elif (defined(__arm__) || defined(__aarch64__))
37  __asm__ __volatile__("yield");
38 #else
39  // Put some pause code in here
40 #endif
41  }
42  else if ( currentCount < 256 ) {
43  sched_yield();
44  }
45  else {
46  struct timespec sleepPeriod;
47  sleepPeriod.tv_sec = 0;
48  sleepPeriod.tv_nsec = 100;
49 
50  struct timespec interPeriod;
51  nanosleep(&sleepPeriod, &interPeriod);
52  }
53  }
54 
55  void lock()
56  {
57  int loop_counter = 0;
58 
59  while (
60  !__sync_bool_compare_and_swap(&lockVal, SST_CORE_INTERPROCESS_UNLOCKED, SST_CORE_INTERPROCESS_LOCKED) ) {
61  processorPause(loop_counter);
62  loop_counter++;
63  }
64  }
65 
66  void unlock()
67  {
68  lockVal = SST_CORE_INTERPROCESS_UNLOCKED;
69  __sync_synchronize();
70  }
71 
72  bool try_lock()
73  {
74  return __sync_bool_compare_and_swap(&lockVal, SST_CORE_INTERPROCESS_UNLOCKED, SST_CORE_INTERPROCESS_LOCKED);
75  }
76 
77 private:
78  volatile int lockVal;
79 };
80 
81 } // namespace Interprocess
82 } // namespace Core
83 } // namespace SST
84 
85 #endif // SST_CORE_INTERPROCESS_MUTEX_H
Definition: sstmutex.h:25