jkummerow@chromium.org | 1456e70 | 2012-03-30 08:38:13 +0000 | [diff] [blame] | 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 |