SDL  2.0
SDL_atomic.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
4 
5  This software is provided 'as-is', without any express or implied
6  warranty. In no event will the authors be held liable for any damages
7  arising from the use of this software.
8 
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12 
13  1. The origin of this software must not be misrepresented; you must not
14  claim that you wrote the original software. If you use this software
15  in a product, an acknowledgment in the product documentation would be
16  appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18  misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20 */
21 #include "../SDL_internal.h"
22 
23 #include "SDL_atomic.h"
24 
25 #if defined(_MSC_VER) && (_MSC_VER >= 1500)
26 #include <intrin.h>
27 #define HAVE_MSC_ATOMICS 1
28 #endif
29 
30 #if defined(__MACOSX__) /* !!! FIXME: should we favor gcc atomics? */
31 #include <libkern/OSAtomic.h>
32 #endif
33 
34 #if !defined(HAVE_GCC_ATOMICS) && defined(__SOLARIS__)
35 #include <atomic.h>
36 #endif
37 
38 /* The __atomic_load_n() intrinsic showed up in different times for different compilers. */
39 #if defined(HAVE_GCC_ATOMICS)
40 # if defined(__clang__)
41 # if __has_builtin(__atomic_load_n)
42  /* !!! FIXME: this advertises as available in the NDK but uses an external symbol we don't have.
43  It might be in a later NDK or we might need an extra library? --ryan. */
44 # if !defined(__ANDROID__)
45 # define HAVE_ATOMIC_LOAD_N 1
46 # endif
47 # endif
48 # elif defined(__GNUC__)
49 # if (__GNUC__ >= 5)
50 # define HAVE_ATOMIC_LOAD_N 1
51 # endif
52 # endif
53 #endif
54 
55 #if defined(__WATCOMC__) && defined(__386__)
56 #define HAVE_WATCOM_ATOMICS
57 extern _inline int _SDL_xchg_watcom(volatile int *a, int v);
58 #pragma aux _SDL_xchg_watcom = \
59  "xchg [ecx], eax" \
60  parm [ecx] [eax] \
61  value [eax] \
62  modify exact [eax];
63 
64 extern _inline unsigned char _SDL_cmpxchg_watcom(volatile int *a, int newval, int oldval);
65 #pragma aux _SDL_cmpxchg_watcom = \
66  "lock cmpxchg [edx], ecx" \
67  "setz al" \
68  parm [edx] [ecx] [eax] \
69  value [al] \
70  modify exact [eax];
71 
72 extern _inline int _SDL_xadd_watcom(volatile int *a, int v);
73 #pragma aux _SDL_xadd_watcom = \
74  "lock xadd [ecx], eax" \
75  parm [ecx] [eax] \
76  value [eax] \
77  modify exact [eax];
78 #endif /* __WATCOMC__ && __386__ */
79 
80 /*
81  If any of the operations are not provided then we must emulate some
82  of them. That means we need a nice implementation of spin locks
83  that avoids the "one big lock" problem. We use a vector of spin
84  locks and pick which one to use based on the address of the operand
85  of the function.
86 
87  To generate the index of the lock we first shift by 3 bits to get
88  rid on the zero bits that result from 32 and 64 bit allignment of
89  data. We then mask off all but 5 bits and use those 5 bits as an
90  index into the table.
91 
92  Picking the lock this way insures that accesses to the same data at
93  the same time will go to the same lock. OTOH, accesses to different
94  data have only a 1/32 chance of hitting the same lock. That should
95  pretty much eliminate the chances of several atomic operations on
96  different data from waiting on the same "big lock". If it isn't
97  then the table of locks can be expanded to a new size so long as
98  the new size is a power of two.
99 
100  Contributed by Bob Pendleton, bob@pendleton.com
101 */
102 
103 #if !defined(HAVE_MSC_ATOMICS) && !defined(HAVE_GCC_ATOMICS) && !defined(__MACOSX__) && !defined(__SOLARIS__) && !defined(HAVE_WATCOM_ATOMICS)
104 #define EMULATE_CAS 1
105 #endif
106 
107 #if EMULATE_CAS
108 static SDL_SpinLock locks[32];
109 
110 static SDL_INLINE void
111 enterLock(void *a)
112 {
113  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
114 
115  SDL_AtomicLock(&locks[index]);
116 }
117 
118 static SDL_INLINE void
119 leaveLock(void *a)
120 {
121  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
122 
123  SDL_AtomicUnlock(&locks[index]);
124 }
125 #endif
126 
127 
128 SDL_bool
129 SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval)
130 {
131 #ifdef HAVE_MSC_ATOMICS
132  return (_InterlockedCompareExchange((long*)&a->value, (long)newval, (long)oldval) == (long)oldval);
133 #elif defined(HAVE_WATCOM_ATOMICS)
134  return (SDL_bool) _SDL_cmpxchg_watcom(&a->value, newval, oldval);
135 #elif defined(HAVE_GCC_ATOMICS)
136  return (SDL_bool) __sync_bool_compare_and_swap(&a->value, oldval, newval);
137 #elif defined(__MACOSX__) /* this is deprecated in 10.12 sdk; favor gcc atomics. */
138  return (SDL_bool) OSAtomicCompareAndSwap32Barrier(oldval, newval, &a->value);
139 #elif defined(__SOLARIS__) && defined(_LP64)
140  return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)&a->value, (uint64_t)oldval, (uint64_t)newval) == oldval);
141 #elif defined(__SOLARIS__) && !defined(_LP64)
142  return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)&a->value, (uint32_t)oldval, (uint32_t)newval) == oldval);
143 #elif EMULATE_CAS
145 
146  enterLock(a);
147  if (a->value == oldval) {
148  a->value = newval;
149  retval = SDL_TRUE;
150  }
151  leaveLock(a);
152 
153  return retval;
154 #else
155  #error Please define your platform.
156 #endif
157 }
158 
159 SDL_bool
160 SDL_AtomicCASPtr(void **a, void *oldval, void *newval)
161 {
162 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
163  return (_InterlockedCompareExchange((long*)a, (long)newval, (long)oldval) == (long)oldval);
164 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
165  return (_InterlockedCompareExchangePointer(a, newval, oldval) == oldval);
166 #elif defined(HAVE_WATCOM_ATOMICS)
167  return (SDL_bool) _SDL_cmpxchg_watcom((int *)a, (long)newval, (long)oldval);
168 #elif defined(HAVE_GCC_ATOMICS)
169  return __sync_bool_compare_and_swap(a, oldval, newval);
170 #elif defined(__MACOSX__) && defined(__LP64__) /* this is deprecated in 10.12 sdk; favor gcc atomics. */
171  return (SDL_bool) OSAtomicCompareAndSwap64Barrier((int64_t)oldval, (int64_t)newval, (int64_t*) a);
172 #elif defined(__MACOSX__) && !defined(__LP64__) /* this is deprecated in 10.12 sdk; favor gcc atomics. */
173  return (SDL_bool) OSAtomicCompareAndSwap32Barrier((int32_t)oldval, (int32_t)newval, (int32_t*) a);
174 #elif defined(__SOLARIS__)
175  return (SDL_bool) (atomic_cas_ptr(a, oldval, newval) == oldval);
176 #elif EMULATE_CAS
178 
179  enterLock(a);
180  if (*a == oldval) {
181  *a = newval;
182  retval = SDL_TRUE;
183  }
184  leaveLock(a);
185 
186  return retval;
187 #else
188  #error Please define your platform.
189 #endif
190 }
191 
192 int
194 {
195 #ifdef HAVE_MSC_ATOMICS
196  return _InterlockedExchange((long*)&a->value, v);
197 #elif defined(HAVE_WATCOM_ATOMICS)
198  return _SDL_xchg_watcom(&a->value, v);
199 #elif defined(HAVE_GCC_ATOMICS)
200  return __sync_lock_test_and_set(&a->value, v);
201 #elif defined(__SOLARIS__) && defined(_LP64)
202  return (int) atomic_swap_64((volatile uint64_t*)&a->value, (uint64_t)v);
203 #elif defined(__SOLARIS__) && !defined(_LP64)
204  return (int) atomic_swap_32((volatile uint32_t*)&a->value, (uint32_t)v);
205 #else
206  int value;
207  do {
208  value = a->value;
209  } while (!SDL_AtomicCAS(a, value, v));
210  return value;
211 #endif
212 }
213 
214 void*
215 SDL_AtomicSetPtr(void **a, void *v)
216 {
217 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
218  return (void *) _InterlockedExchange((long *)a, (long) v);
219 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
220  return _InterlockedExchangePointer(a, v);
221 #elif defined(HAVE_WATCOM_ATOMICS)
222  return (void *) _SDL_xchg_watcom((int *)a, (long)v);
223 #elif defined(HAVE_GCC_ATOMICS)
224  return __sync_lock_test_and_set(a, v);
225 #elif defined(__SOLARIS__)
226  return atomic_swap_ptr(a, v);
227 #else
228  void *value;
229  do {
230  value = *a;
231  } while (!SDL_AtomicCASPtr(a, value, v));
232  return value;
233 #endif
234 }
235 
236 int
238 {
239 #ifdef HAVE_MSC_ATOMICS
240  return _InterlockedExchangeAdd((long*)&a->value, v);
241 #elif defined(HAVE_WATCOM_ATOMICS)
242  return _SDL_xadd_watcom(&a->value, v);
243 #elif defined(HAVE_GCC_ATOMICS)
244  return __sync_fetch_and_add(&a->value, v);
245 #elif defined(__SOLARIS__)
246  int pv = a->value;
247  membar_consumer();
248 #if defined(_LP64)
249  atomic_add_64((volatile uint64_t*)&a->value, v);
250 #elif !defined(_LP64)
251  atomic_add_32((volatile uint32_t*)&a->value, v);
252 #endif
253  return pv;
254 #else
255  int value;
256  do {
257  value = a->value;
258  } while (!SDL_AtomicCAS(a, value, (value + v)));
259  return value;
260 #endif
261 }
262 
263 int
265 {
266 #ifdef HAVE_ATOMIC_LOAD_N
267  return __atomic_load_n(&a->value, __ATOMIC_SEQ_CST);
268 #else
269  int value;
270  do {
271  value = a->value;
272  } while (!SDL_AtomicCAS(a, value, value));
273  return value;
274 #endif
275 }
276 
277 void *
279 {
280 #ifdef HAVE_ATOMIC_LOAD_N
281  return __atomic_load_n(a, __ATOMIC_SEQ_CST);
282 #else
283  void *value;
284  do {
285  value = *a;
286  } while (!SDL_AtomicCASPtr(a, value, value));
287  return value;
288 #endif
289 }
290 
291 void
293 {
295 }
296 
297 void
299 {
301 }
302 
303 /* vi: set ts=4 sw=4 expandtab: */
void * SDL_AtomicGetPtr(void **a)
Get the value of a pointer atomically.
Definition: SDL_atomic.c:278
const GLdouble * v
Definition: SDL_opengl.h:2064
#define SDL_AtomicLock
signed int int32_t
#define SDL_MemoryBarrierRelease()
Definition: SDL_atomic.h:189
A type representing an atomic integer value. It is a struct so people don&#39;t accidentally use numeric ...
Definition: SDL_atomic.h:198
unsigned long long uint64_t
int SDL_AtomicGet(SDL_atomic_t *a)
Get the value of an atomic variable.
Definition: SDL_atomic.c:264
SDL_bool SDL_AtomicCASPtr(void **a, void *oldval, void *newval)
Set a pointer to a new value if it is currently an old value.
Definition: SDL_atomic.c:160
#define SDL_MemoryBarrierAcquire()
Definition: SDL_atomic.h:190
#define SDL_AtomicUnlock
SDL_bool retval
void * SDL_AtomicSetPtr(void **a, void *v)
Set a pointer to a value atomically.
Definition: SDL_atomic.c:215
GLsizei const GLfloat * value
static SDL_INLINE void leaveLock(void *a)
Definition: SDL_atomic.c:119
int SDL_AtomicSet(SDL_atomic_t *a, int v)
Set an atomic variable to a value.
Definition: SDL_atomic.c:193
static SDL_INLINE void enterLock(void *a)
Definition: SDL_atomic.c:111
unsigned int uintptr_t
GLuint index
SDL_bool
Definition: SDL_stdinc.h:139
unsigned int uint32_t
int SDL_AtomicAdd(SDL_atomic_t *a, int v)
Add to an atomic variable.
Definition: SDL_atomic.c:237
#define SDL_INLINE
Definition: begin_code.h:131
static SDL_SpinLock locks[32]
Definition: SDL_atomic.c:108
void SDL_MemoryBarrierAcquireFunction(void)
Definition: SDL_atomic.c:298
int SDL_SpinLock
Definition: SDL_atomic.h:89
GLboolean GLboolean GLboolean GLboolean a
void SDL_MemoryBarrierReleaseFunction(void)
Definition: SDL_atomic.c:292
SDL_bool SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval)
Set an atomic variable to a new value if it is currently an old value.
Definition: SDL_atomic.c:129
signed long long int64_t