SDL  2.0
SDL_atomic.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2019 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 SDL_COMPILE_TIME_ASSERT(intsize, 4==sizeof(int));
57 #define HAVE_WATCOM_ATOMICS
58 extern _inline int _SDL_xchg_watcom(volatile int *a, int v);
59 #pragma aux _SDL_xchg_watcom = \
60  "lock xchg [ecx], eax" \
61  parm [ecx] [eax] \
62  value [eax] \
63  modify exact [eax];
64 
65 extern _inline unsigned char _SDL_cmpxchg_watcom(volatile int *a, int newval, int oldval);
66 #pragma aux _SDL_cmpxchg_watcom = \
67  "lock cmpxchg [edx], ecx" \
68  "setz al" \
69  parm [edx] [ecx] [eax] \
70  value [al] \
71  modify exact [eax];
72 
73 extern _inline int _SDL_xadd_watcom(volatile int *a, int v);
74 #pragma aux _SDL_xadd_watcom = \
75  "lock xadd [ecx], eax" \
76  parm [ecx] [eax] \
77  value [eax] \
78  modify exact [eax];
79 #endif /* __WATCOMC__ && __386__ */
80 
81 /*
82  If any of the operations are not provided then we must emulate some
83  of them. That means we need a nice implementation of spin locks
84  that avoids the "one big lock" problem. We use a vector of spin
85  locks and pick which one to use based on the address of the operand
86  of the function.
87 
88  To generate the index of the lock we first shift by 3 bits to get
89  rid on the zero bits that result from 32 and 64 bit allignment of
90  data. We then mask off all but 5 bits and use those 5 bits as an
91  index into the table.
92 
93  Picking the lock this way insures that accesses to the same data at
94  the same time will go to the same lock. OTOH, accesses to different
95  data have only a 1/32 chance of hitting the same lock. That should
96  pretty much eliminate the chances of several atomic operations on
97  different data from waiting on the same "big lock". If it isn't
98  then the table of locks can be expanded to a new size so long as
99  the new size is a power of two.
100 
101  Contributed by Bob Pendleton, bob@pendleton.com
102 */
103 
104 #if !defined(HAVE_MSC_ATOMICS) && !defined(HAVE_GCC_ATOMICS) && !defined(__MACOSX__) && !defined(__SOLARIS__) && !defined(HAVE_WATCOM_ATOMICS)
105 #define EMULATE_CAS 1
106 #endif
107 
108 #if EMULATE_CAS
109 static SDL_SpinLock locks[32];
110 
111 static SDL_INLINE void
112 enterLock(void *a)
113 {
114  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
115 
117 }
118 
119 static SDL_INLINE void
120 leaveLock(void *a)
121 {
122  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
123 
125 }
126 #endif
127 
128 
129 SDL_bool
130 SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval)
131 {
132 #ifdef HAVE_MSC_ATOMICS
133  return (_InterlockedCompareExchange((long*)&a->value, (long)newval, (long)oldval) == (long)oldval);
134 #elif defined(HAVE_WATCOM_ATOMICS)
135  return (SDL_bool) _SDL_cmpxchg_watcom(&a->value, newval, oldval);
136 #elif defined(HAVE_GCC_ATOMICS)
137  return (SDL_bool) __sync_bool_compare_and_swap(&a->value, oldval, newval);
138 #elif defined(__MACOSX__) /* this is deprecated in 10.12 sdk; favor gcc atomics. */
139  return (SDL_bool) OSAtomicCompareAndSwap32Barrier(oldval, newval, &a->value);
140 #elif defined(__SOLARIS__) && defined(_LP64)
141  return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)&a->value, (uint64_t)oldval, (uint64_t)newval) == oldval);
142 #elif defined(__SOLARIS__) && !defined(_LP64)
143  return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)&a->value, (uint32_t)oldval, (uint32_t)newval) == oldval);
144 #elif EMULATE_CAS
146 
147  enterLock(a);
148  if (a->value == oldval) {
149  a->value = newval;
150  retval = SDL_TRUE;
151  }
152  leaveLock(a);
153 
154  return retval;
155 #else
156  #error Please define your platform.
157 #endif
158 }
159 
160 SDL_bool
161 SDL_AtomicCASPtr(void **a, void *oldval, void *newval)
162 {
163 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
164  return (_InterlockedCompareExchange((long*)a, (long)newval, (long)oldval) == (long)oldval);
165 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
166  return (_InterlockedCompareExchangePointer(a, newval, oldval) == oldval);
167 #elif defined(HAVE_WATCOM_ATOMICS)
168  return (SDL_bool) _SDL_cmpxchg_watcom((int *)a, (long)newval, (long)oldval);
169 #elif defined(HAVE_GCC_ATOMICS)
170  return __sync_bool_compare_and_swap(a, oldval, newval);
171 #elif defined(__MACOSX__) && defined(__LP64__) /* this is deprecated in 10.12 sdk; favor gcc atomics. */
172  return (SDL_bool) OSAtomicCompareAndSwap64Barrier((int64_t)oldval, (int64_t)newval, (int64_t*) a);
173 #elif defined(__MACOSX__) && !defined(__LP64__) /* this is deprecated in 10.12 sdk; favor gcc atomics. */
174  return (SDL_bool) OSAtomicCompareAndSwap32Barrier((int32_t)oldval, (int32_t)newval, (int32_t*) a);
175 #elif defined(__SOLARIS__)
176  return (SDL_bool) (atomic_cas_ptr(a, oldval, newval) == oldval);
177 #elif EMULATE_CAS
179 
180  enterLock(a);
181  if (*a == oldval) {
182  *a = newval;
183  retval = SDL_TRUE;
184  }
185  leaveLock(a);
186 
187  return retval;
188 #else
189  #error Please define your platform.
190 #endif
191 }
192 
193 int
195 {
196 #ifdef HAVE_MSC_ATOMICS
197  return _InterlockedExchange((long*)&a->value, v);
198 #elif defined(HAVE_WATCOM_ATOMICS)
199  return _SDL_xchg_watcom(&a->value, v);
200 #elif defined(HAVE_GCC_ATOMICS)
201  return __sync_lock_test_and_set(&a->value, v);
202 #elif defined(__SOLARIS__) && defined(_LP64)
203  return (int) atomic_swap_64((volatile uint64_t*)&a->value, (uint64_t)v);
204 #elif defined(__SOLARIS__) && !defined(_LP64)
205  return (int) atomic_swap_32((volatile uint32_t*)&a->value, (uint32_t)v);
206 #else
207  int value;
208  do {
209  value = a->value;
210  } while (!SDL_AtomicCAS(a, value, v));
211  return value;
212 #endif
213 }
214 
215 void*
216 SDL_AtomicSetPtr(void **a, void *v)
217 {
218 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
219  return (void *) _InterlockedExchange((long *)a, (long) v);
220 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
221  return _InterlockedExchangePointer(a, v);
222 #elif defined(HAVE_WATCOM_ATOMICS)
223  return (void *) _SDL_xchg_watcom((int *)a, (long)v);
224 #elif defined(HAVE_GCC_ATOMICS)
225  return __sync_lock_test_and_set(a, v);
226 #elif defined(__SOLARIS__)
227  return atomic_swap_ptr(a, v);
228 #else
229  void *value;
230  do {
231  value = *a;
232  } while (!SDL_AtomicCASPtr(a, value, v));
233  return value;
234 #endif
235 }
236 
237 int
239 {
240 #ifdef HAVE_MSC_ATOMICS
241  return _InterlockedExchangeAdd((long*)&a->value, v);
242 #elif defined(HAVE_WATCOM_ATOMICS)
243  return _SDL_xadd_watcom(&a->value, v);
244 #elif defined(HAVE_GCC_ATOMICS)
245  return __sync_fetch_and_add(&a->value, v);
246 #elif defined(__SOLARIS__)
247  int pv = a->value;
248  membar_consumer();
249 #if defined(_LP64)
250  atomic_add_64((volatile uint64_t*)&a->value, v);
251 #elif !defined(_LP64)
252  atomic_add_32((volatile uint32_t*)&a->value, v);
253 #endif
254  return pv;
255 #else
256  int value;
257  do {
258  value = a->value;
259  } while (!SDL_AtomicCAS(a, value, (value + v)));
260  return value;
261 #endif
262 }
263 
264 int
266 {
267 #ifdef HAVE_ATOMIC_LOAD_N
268  return __atomic_load_n(&a->value, __ATOMIC_SEQ_CST);
269 #else
270  int value;
271  do {
272  value = a->value;
273  } while (!SDL_AtomicCAS(a, value, value));
274  return value;
275 #endif
276 }
277 
278 void *
280 {
281 #ifdef HAVE_ATOMIC_LOAD_N
282  return __atomic_load_n(a, __ATOMIC_SEQ_CST);
283 #else
284  void *value;
285  do {
286  value = *a;
287  } while (!SDL_AtomicCASPtr(a, value, value));
288  return value;
289 #endif
290 }
291 
292 #ifdef SDL_MEMORY_BARRIER_USES_FUNCTION
293 #error This file should be built in arm mode so the mcr instruction is available for memory barriers
294 #endif
295 
296 void
298 {
300 }
301 
302 void
304 {
306 }
307 
308 /* vi: set ts=4 sw=4 expandtab: */
SDL_MemoryBarrierReleaseFunction
void SDL_MemoryBarrierReleaseFunction(void)
Definition: SDL_atomic.c:297
SDL_MemoryBarrierAcquireFunction
void SDL_MemoryBarrierAcquireFunction(void)
Definition: SDL_atomic.c:303
SDL_atomic.h
leaveLock
static SDL_INLINE void leaveLock(void *a)
Definition: SDL_atomic.c:120
locks
static SDL_SpinLock locks[32]
Definition: SDL_atomic.c:109
SDL_MemoryBarrierRelease
#define SDL_MemoryBarrierRelease()
Definition: SDL_atomic.h:207
SDL_AtomicLock
#define SDL_AtomicLock
Definition: SDL_dynapi_overrides.h:64
SDL_AtomicAdd
int SDL_AtomicAdd(SDL_atomic_t *a, int v)
Add to an atomic variable.
Definition: SDL_atomic.c:238
index
GLuint index
Definition: SDL_opengl_glext.h:660
a
GLboolean GLboolean GLboolean GLboolean a
Definition: SDL_opengl_glext.h:1109
v
const GLdouble * v
Definition: SDL_opengl.h:2063
SDL_AtomicGetPtr
void * SDL_AtomicGetPtr(void **a)
Get the value of a pointer atomically.
Definition: SDL_atomic.c:279
SDL_COMPILE_TIME_ASSERT
#define SDL_COMPILE_TIME_ASSERT(name, x)
Definition: SDL_stdinc.h:312
SDL_AtomicUnlock
#define SDL_AtomicUnlock
Definition: SDL_dynapi_overrides.h:65
retval
SDL_bool retval
Definition: testgamecontroller.c:65
int32_t
signed int int32_t
Definition: SDL_config_windows.h:62
SDL_INLINE
#define SDL_INLINE
Definition: begin_code.h:134
SDL_AtomicCASPtr
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:161
SDL_AtomicSet
int SDL_AtomicSet(SDL_atomic_t *a, int v)
Set an atomic variable to a value.
Definition: SDL_atomic.c:194
SDL_FALSE
Definition: SDL_stdinc.h:163
enterLock
static SDL_INLINE void enterLock(void *a)
Definition: SDL_atomic.c:112
SDL_SpinLock
int SDL_SpinLock
Definition: SDL_atomic.h:89
SDL_bool
SDL_bool
Definition: SDL_stdinc.h:161
SDL_AtomicSetPtr
void * SDL_AtomicSetPtr(void **a, void *v)
Set a pointer to a value atomically.
Definition: SDL_atomic.c:216
uint32_t
unsigned int uint32_t
Definition: SDL_config_windows.h:63
value
GLsizei const GLfloat * value
Definition: SDL_opengl_glext.h:698
SDL_TRUE
Definition: SDL_stdinc.h:164
SDL_MemoryBarrierAcquire
#define SDL_MemoryBarrierAcquire()
Definition: SDL_atomic.h:208
SDL_atomic_t
A type representing an atomic integer value. It is a struct so people don't accidentally use numeric ...
Definition: SDL_atomic.h:216
SDL_AtomicGet
int SDL_AtomicGet(SDL_atomic_t *a)
Get the value of an atomic variable.
Definition: SDL_atomic.c:265
SDL_AtomicCAS
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:130
uint64_t
unsigned long long uint64_t
Definition: SDL_config_windows.h:65
int64_t
signed long long int64_t
Definition: SDL_config_windows.h:64
uintptr_t
unsigned int uintptr_t
Definition: SDL_config_windows.h:70