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1 // Copyright 2012 the V8 project authors. All rights reserved. | |
2 // Redistribution and use in source and binary forms, with or without | |
3 // modification, are permitted provided that the following conditions are | |
4 // met: | |
5 // | |
6 // * Redistributions of source code must retain the above copyright | |
7 // notice, this list of conditions and the following disclaimer. | |
8 // * Redistributions in binary form must reproduce the above | |
9 // copyright notice, this list of conditions and the following | |
10 // disclaimer in the documentation and/or other materials provided | |
11 // with the distribution. | |
12 // * Neither the name of Google Inc. nor the names of its | |
13 // contributors may be used to endorse or promote products derived | |
14 // from this software without specific prior written permission. | |
15 // | |
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
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( | |
57 once, ONCE_STATE_UNINITIALIZED, ONCE_STATE_EXECUTING_FUNCTION); | |
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); | |
62 Release_Store(once, ONCE_STATE_DONE); | |
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 | |
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