PortAudio  2.0
pa_memorybarrier.h
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1 /*
2  * $Id: pa_memorybarrier.h 1240 2007-07-17 13:05:07Z bjornroche $
3  * Portable Audio I/O Library
4  * Memory barrier utilities
5  *
6  * Author: Bjorn Roche, XO Audio, LLC
7  *
8  * This program uses the PortAudio Portable Audio Library.
9  * For more information see: http://www.portaudio.com
10  * Copyright (c) 1999-2000 Ross Bencina and Phil Burk
11  *
12  * Permission is hereby granted, free of charge, to any person obtaining
13  * a copy of this software and associated documentation files
14  * (the "Software"), to deal in the Software without restriction,
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19  *
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31 
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33  * The text above constitutes the entire PortAudio license; however,
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42 
48 /****************
49  * Some memory barrier primitives based on the system.
50  * right now only OS X, FreeBSD, and Linux are supported. In addition to providing
51  * memory barriers, these functions should ensure that data cached in registers
52  * is written out to cache where it can be snooped by other CPUs. (ie, the volatile
53  * keyword should not be required)
54  *
55  * the primitives that must be defined are:
56  *
57  * PaUtil_FullMemoryBarrier()
58  * PaUtil_ReadMemoryBarrier()
59  * PaUtil_WriteMemoryBarrier()
60  *
61  ****************/
62 
63 #if defined(__APPLE__)
64 /* Support for the atomic library was added in C11.
65  */
66 # if (__STDC_VERSION__ < 201112L) || defined(__STDC_NO_ATOMICS__)
67 # include <libkern/OSAtomic.h>
68  /* Here are the memory barrier functions. Mac OS X only provides
69  full memory barriers, so the three types of barriers are the same,
70  however, these barriers are superior to compiler-based ones.
71  These were deprecated in MacOS 10.12. */
72 # define PaUtil_FullMemoryBarrier() OSMemoryBarrier()
73 # define PaUtil_ReadMemoryBarrier() OSMemoryBarrier()
74 # define PaUtil_WriteMemoryBarrier() OSMemoryBarrier()
75 # else
76 # include <stdatomic.h>
77 # define PaUtil_FullMemoryBarrier() atomic_thread_fence(memory_order_seq_cst)
78 # define PaUtil_ReadMemoryBarrier() atomic_thread_fence(memory_order_acquire)
79 # define PaUtil_WriteMemoryBarrier() atomic_thread_fence(memory_order_release)
80 # endif
81 #elif defined(__GNUC__)
82  /* GCC >= 4.1 has built-in intrinsics. We'll use those */
83 # if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
84 # define PaUtil_FullMemoryBarrier() __sync_synchronize()
85 # define PaUtil_ReadMemoryBarrier() __sync_synchronize()
86 # define PaUtil_WriteMemoryBarrier() __sync_synchronize()
87  /* as a fallback, GCC understands volatile asm and "memory" to mean it
88  * should not reorder memory read/writes */
89  /* Note that it is not clear that any compiler actually defines __PPC__,
90  * it can probably removed safely. */
91 # elif defined( __ppc__ ) || defined( __powerpc__) || defined( __PPC__ )
92 # define PaUtil_FullMemoryBarrier() asm volatile("sync":::"memory")
93 # define PaUtil_ReadMemoryBarrier() asm volatile("sync":::"memory")
94 # define PaUtil_WriteMemoryBarrier() asm volatile("sync":::"memory")
95 # elif defined( __i386__ ) || defined( __i486__ ) || defined( __i586__ ) || \
96  defined( __i686__ ) || defined( __x86_64__ )
97 # define PaUtil_FullMemoryBarrier() asm volatile("mfence":::"memory")
98 # define PaUtil_ReadMemoryBarrier() asm volatile("lfence":::"memory")
99 # define PaUtil_WriteMemoryBarrier() asm volatile("sfence":::"memory")
100 # else
101 # ifdef ALLOW_SMP_DANGERS
102 # warning Memory barriers not defined on this system or system unknown
103 # warning For SMP safety, you should fix this.
104 # define PaUtil_FullMemoryBarrier()
105 # define PaUtil_ReadMemoryBarrier()
106 # define PaUtil_WriteMemoryBarrier()
107 # else
108 # error Memory barriers are not defined on this system. You can still compile by defining ALLOW_SMP_DANGERS, but SMP safety will not be guaranteed.
109 # endif
110 # endif
111 #elif (_MSC_VER >= 1400) && !defined(_WIN32_WCE)
112 # include <intrin.h>
113 # pragma intrinsic(_ReadWriteBarrier)
114 # pragma intrinsic(_ReadBarrier)
115 # pragma intrinsic(_WriteBarrier)
116 /* note that MSVC intrinsics _ReadWriteBarrier(), _ReadBarrier(), _WriteBarrier() are just compiler barriers *not* memory barriers */
117 # define PaUtil_FullMemoryBarrier() _ReadWriteBarrier()
118 # define PaUtil_ReadMemoryBarrier() _ReadBarrier()
119 # define PaUtil_WriteMemoryBarrier() _WriteBarrier()
120 #elif defined(_WIN32_WCE)
121 # define PaUtil_FullMemoryBarrier()
122 # define PaUtil_ReadMemoryBarrier()
123 # define PaUtil_WriteMemoryBarrier()
124 #elif defined(_MSC_VER) || defined(__BORLANDC__)
125 # define PaUtil_FullMemoryBarrier() _asm { lock add [esp], 0 }
126 # define PaUtil_ReadMemoryBarrier() _asm { lock add [esp], 0 }
127 # define PaUtil_WriteMemoryBarrier() _asm { lock add [esp], 0 }
128 #else
129 # ifdef ALLOW_SMP_DANGERS
130 # warning Memory barriers not defined on this system or system unknown
131 # warning For SMP safety, you should fix this.
132 # define PaUtil_FullMemoryBarrier()
133 # define PaUtil_ReadMemoryBarrier()
134 # define PaUtil_WriteMemoryBarrier()
135 # else
136 # error Memory barriers are not defined on this system. You can still compile by defining ALLOW_SMP_DANGERS, but SMP safety will not be guaranteed.
137 # endif
138 #endif
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