SDL  2.0
SDL_atomic.c File Reference
#include "../SDL_internal.h"
#include "SDL_atomic.h"
+ Include dependency graph for SDL_atomic.c:

Go to the source code of this file.

Macros

#define EMULATE_CAS   1
 

Functions

static SDL_INLINE void enterLock (void *a)
 
static SDL_INLINE void leaveLock (void *a)
 
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. More...
 
SDL_bool SDL_AtomicCASPtr (void **a, void *oldval, void *newval)
 Set a pointer to a new value if it is currently an old value. More...
 
int SDL_AtomicSet (SDL_atomic_t *a, int v)
 Set an atomic variable to a value. More...
 
voidSDL_AtomicSetPtr (void **a, void *v)
 Set a pointer to a value atomically. More...
 
int SDL_AtomicAdd (SDL_atomic_t *a, int v)
 Add to an atomic variable. More...
 
int SDL_AtomicGet (SDL_atomic_t *a)
 Get the value of an atomic variable. More...
 
voidSDL_AtomicGetPtr (void **a)
 Get the value of a pointer atomically. More...
 
void SDL_MemoryBarrierReleaseFunction (void)
 
void SDL_MemoryBarrierAcquireFunction (void)
 

Variables

static SDL_SpinLock locks [32]
 

Macro Definition Documentation

◆ EMULATE_CAS

#define EMULATE_CAS   1

Definition at line 105 of file SDL_atomic.c.

Function Documentation

◆ enterLock()

static SDL_INLINE void enterLock ( void a)
static

Definition at line 112 of file SDL_atomic.c.

113 {
114  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
115 
117 }

References locks, and SDL_AtomicLock.

Referenced by SDL_AtomicCAS(), and SDL_AtomicCASPtr().

◆ leaveLock()

static SDL_INLINE void leaveLock ( void a)
static

Definition at line 120 of file SDL_atomic.c.

121 {
122  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
123 
125 }

References locks, and SDL_AtomicUnlock.

Referenced by SDL_AtomicCAS(), and SDL_AtomicCASPtr().

◆ SDL_AtomicAdd()

int SDL_AtomicAdd ( SDL_atomic_t a,
int  v 
)

Add to an atomic variable.

Returns
The previous value of the atomic variable.
Note
This same style can be used for any number operation

Definition at line 238 of file SDL_atomic.c.

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 }

References SDL_AtomicCAS().

◆ 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.

Returns
SDL_TRUE if the atomic variable was set, SDL_FALSE otherwise.
Note
If you don't know what this function is for, you shouldn't use it!

Definition at line 130 of file SDL_atomic.c.

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 }

References enterLock(), leaveLock(), retval, SDL_FALSE, and SDL_TRUE.

Referenced by SDL_AtomicAdd(), SDL_AtomicGet(), and SDL_AtomicSet().

◆ 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.

Returns
SDL_TRUE if the pointer was set, SDL_FALSE otherwise.
Note
If you don't know what this function is for, you shouldn't use it!

Definition at line 161 of file SDL_atomic.c.

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 }

References enterLock(), leaveLock(), retval, SDL_FALSE, and SDL_TRUE.

Referenced by SDL_AtomicGetPtr(), and SDL_AtomicSetPtr().

◆ SDL_AtomicGet()

int SDL_AtomicGet ( SDL_atomic_t a)

Get the value of an atomic variable.

Definition at line 265 of file SDL_atomic.c.

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 }

References SDL_AtomicCAS().

◆ SDL_AtomicGetPtr()

void* SDL_AtomicGetPtr ( void **  a)

Get the value of a pointer atomically.

Definition at line 279 of file SDL_atomic.c.

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 }

References SDL_AtomicCASPtr().

◆ SDL_AtomicSet()

int SDL_AtomicSet ( SDL_atomic_t a,
int  v 
)

Set an atomic variable to a value.

Returns
The previous value of the atomic variable.

Definition at line 194 of file SDL_atomic.c.

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 }

References SDL_AtomicCAS().

◆ SDL_AtomicSetPtr()

void* SDL_AtomicSetPtr ( void **  a,
void v 
)

Set a pointer to a value atomically.

Returns
The previous value of the pointer.

Definition at line 216 of file SDL_atomic.c.

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 }

References SDL_AtomicCASPtr().

◆ SDL_MemoryBarrierAcquireFunction()

void SDL_MemoryBarrierAcquireFunction ( void  )

Definition at line 303 of file SDL_atomic.c.

304 {
306 }

References SDL_MemoryBarrierAcquire.

◆ SDL_MemoryBarrierReleaseFunction()

void SDL_MemoryBarrierReleaseFunction ( void  )

Memory barriers are designed to prevent reads and writes from being reordered by the compiler and being seen out of order on multi-core CPUs.

A typical pattern would be for thread A to write some data and a flag, and for thread B to read the flag and get the data. In this case you would insert a release barrier between writing the data and the flag, guaranteeing that the data write completes no later than the flag is written, and you would insert an acquire barrier between reading the flag and reading the data, to ensure that all the reads associated with the flag have completed.

In this pattern you should always see a release barrier paired with an acquire barrier and you should gate the data reads/writes with a single flag variable.

For more information on these semantics, take a look at the blog post: http://preshing.com/20120913/acquire-and-release-semantics

Definition at line 297 of file SDL_atomic.c.

298 {
300 }

References SDL_MemoryBarrierRelease.

Variable Documentation

◆ locks

SDL_SpinLock locks[32]
static

Definition at line 109 of file SDL_atomic.c.

Referenced by enterLock(), and leaveLock().

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
index
GLuint index
Definition: SDL_opengl_glext.h:663
a
GLboolean GLboolean GLboolean GLboolean a
Definition: SDL_opengl_glext.h:1112
v
const GLdouble * v
Definition: SDL_opengl.h:2064
SDL_FALSE
@ SDL_FALSE
Definition: SDL_stdinc.h:163
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_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
enterLock
static SDL_INLINE void enterLock(void *a)
Definition: SDL_atomic.c:112
uint32_t
unsigned int uint32_t
Definition: SDL_config_windows.h:63
SDL_TRUE
@ SDL_TRUE
Definition: SDL_stdinc.h:164
value
GLsizei const GLfloat * value
Definition: SDL_opengl_glext.h:701
SDL_MemoryBarrierAcquire
#define SDL_MemoryBarrierAcquire()
Definition: SDL_atomic.h:208
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
SDL_bool
SDL_bool
Definition: SDL_stdinc.h:161
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