1 // Copyright (c) 2010 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // This file provides a macro ONLY for use in testing. 6 // DO NOT USE IN PRODUCTION CODE. There are much better ways to wait. 7 8 // This code is very helpful in testing multi-threaded code, without depending 9 // on almost any primitives. This is especially helpful if you are testing 10 // those primitive multi-threaded constructs. 11 12 // We provide a simple one argument spin wait (for 1 second), and a generic 13 // spin wait (for longer periods of time). 14 15 #ifndef BASE_SPIN_WAIT_H_ 16 #define BASE_SPIN_WAIT_H_ 17 #pragma once 18 19 #include "base/threading/platform_thread.h" 20 #include "base/time.h" 21 22 // Provide a macro that will wait no longer than 1 second for an asynchronous 23 // change is the value of an expression. 24 // A typical use would be: 25 // 26 // SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(0 == f(x)); 27 // 28 // The expression will be evaluated repeatedly until it is true, or until 29 // the time (1 second) expires. 30 // Since tests generally have a 5 second watch dog timer, this spin loop is 31 // typically used to get the padding needed on a given test platform to assure 32 // that the test passes, even if load varies, and external events vary. 33 34 #define SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(expression) \ 35 SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(base::TimeDelta::FromSeconds(1), \ 36 (expression)) 37 38 #define SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(delta, expression) do { \ 39 base::TimeTicks start = base::TimeTicks::Now(); \ 40 const base::TimeDelta kTimeout = delta; \ 41 while (!(expression)) { \ 42 if (kTimeout < base::TimeTicks::Now() - start) { \ 43 EXPECT_LE((base::TimeTicks::Now() - start).InMilliseconds(), \ 44 kTimeout.InMilliseconds()) << "Timed out"; \ 45 break; \ 46 } \ 47 base::PlatformThread::Sleep(50); \ 48 } \ 49 } while (0) 50 51 #endif // BASE_SPIN_WAIT_H_ 52