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once.cc
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27 
28 #include "once.h"
29 
30 #ifdef _WIN32
31 #include <windows.h>
32 #else
33 #include <sched.h>
34 #endif
35 
36 #include "atomicops.h"
37 #include "checks.h"
38 
39 namespace v8 {
40 namespace internal {
41 
42 void CallOnceImpl(OnceType* once, PointerArgFunction init_func, void* arg) {
43  AtomicWord state = Acquire_Load(once);
44  // Fast path. The provided function was already executed.
45  if (state == ONCE_STATE_DONE) {
46  return;
47  }
48 
49  // The function execution did not complete yet. The once object can be in one
50  // of the two following states:
51  // - UNINITIALIZED: We are the first thread calling this function.
52  // - EXECUTING_FUNCTION: Another thread is already executing the function.
53  //
54  // First, try to change the state from UNINITIALIZED to EXECUTING_FUNCTION
55  // atomically.
56  state = Acquire_CompareAndSwap(
58  if (state == ONCE_STATE_UNINITIALIZED) {
59  // We are the first thread to call this function, so we have to call the
60  // function.
61  init_func(arg);
63  } else {
64  // Another thread has already started executing the function. We need to
65  // wait until it completes the initialization.
66  while (state == ONCE_STATE_EXECUTING_FUNCTION) {
67 #ifdef _WIN32
68  ::Sleep(0);
69 #else
70  sched_yield();
71 #endif
72  state = Acquire_Load(once);
73  }
74  }
75 }
76 
77 } } // namespace v8::internal
void CallOnceImpl(OnceType *once, PointerArgFunction init_func, void *arg)
Definition: once.cc:42
void(* PointerArgFunction)(void *arg)
Definition: once.h:96
AtomicWord OnceType
Definition: once.h:83
intptr_t AtomicWord
Definition: atomicops.h:75
void Release_Store(volatile Atomic32 *ptr, Atomic32 value)
Atomic32 Acquire_Load(volatile const Atomic32 *ptr)
Atomic32 Acquire_CompareAndSwap(volatile Atomic32 *ptr, Atomic32 old_value, Atomic32 new_value)