1 /* 2 * Copyright (c) 2016 Apple Inc. All rights reserved. 3 * 4 * @APPLE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. Please obtain a copy of the License at 10 * http://www.opensource.apple.com/apsl/ and read it before using this 11 * file. 12 * 13 * The Original Code and all software distributed under the License are 14 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 15 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 16 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 18 * Please see the License for the specific language governing rights and 19 * limitations under the License. 20 * 21 * @APPLE_LICENSE_HEADER_END@ 22 */ 23 #include <mach/mach_time.h> 24 25 extern kern_return_t 26 mach_timebase_info_trap(mach_timebase_info_t info); 27 28 kern_return_t mach_timebase_info(mach_timebase_info_t info)29mach_timebase_info(mach_timebase_info_t info) 30 { 31 static mach_timebase_info_data_t cached_info; 32 33 /* 34 * This is racy, but because it is safe to initialize twice we avoid a 35 * barrier in the fast path by risking double initialization. 36 */ 37 if (cached_info.numer == 0 || cached_info.denom == 0) { 38 kern_return_t kr = mach_timebase_info_trap(&cached_info); 39 if (kr != KERN_SUCCESS) { 40 return kr; 41 } 42 } 43 44 info->numer = cached_info.numer; 45 info->denom = cached_info.denom; 46 47 return KERN_SUCCESS; 48 } 49