SDL  2.0
SDL_atomic.c
Go to the documentation of this file.
1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2016 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 /*
39  If any of the operations are not provided then we must emulate some
40  of them. That means we need a nice implementation of spin locks
41  that avoids the "one big lock" problem. We use a vector of spin
42  locks and pick which one to use based on the address of the operand
43  of the function.
44 
45  To generate the index of the lock we first shift by 3 bits to get
46  rid on the zero bits that result from 32 and 64 bit allignment of
47  data. We then mask off all but 5 bits and use those 5 bits as an
48  index into the table.
49 
50  Picking the lock this way insures that accesses to the same data at
51  the same time will go to the same lock. OTOH, accesses to different
52  data have only a 1/32 chance of hitting the same lock. That should
53  pretty much eliminate the chances of several atomic operations on
54  different data from waiting on the same "big lock". If it isn't
55  then the table of locks can be expanded to a new size so long as
56  the new size is a power of two.
57 
58  Contributed by Bob Pendleton, bob@pendleton.com
59 */
60 
61 #if !defined(HAVE_MSC_ATOMICS) && !defined(HAVE_GCC_ATOMICS) && !defined(__MACOSX__) && !defined(__SOLARIS__)
62 #define EMULATE_CAS 1
63 #endif
64 
65 #if EMULATE_CAS
66 static SDL_SpinLock locks[32];
67 
68 static SDL_INLINE void
69 enterLock(void *a)
70 {
71  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
72 
73  SDL_AtomicLock(&locks[index]);
74 }
75 
76 static SDL_INLINE void
77 leaveLock(void *a)
78 {
79  uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
80 
81  SDL_AtomicUnlock(&locks[index]);
82 }
83 #endif
84 
85 
87 SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval)
88 {
89 #ifdef HAVE_MSC_ATOMICS
90  return (_InterlockedCompareExchange((long*)&a->value, (long)newval, (long)oldval) == (long)oldval);
91 #elif defined(__MACOSX__) /* !!! FIXME: should we favor gcc atomics? */
92  return (SDL_bool) OSAtomicCompareAndSwap32Barrier(oldval, newval, &a->value);
93 #elif defined(HAVE_GCC_ATOMICS)
94  return (SDL_bool) __sync_bool_compare_and_swap(&a->value, oldval, newval);
95 #elif defined(__SOLARIS__) && defined(_LP64)
96  return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)&a->value, (uint64_t)oldval, (uint64_t)newval) == oldval);
97 #elif defined(__SOLARIS__) && !defined(_LP64)
98  return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)&a->value, (uint32_t)oldval, (uint32_t)newval) == oldval);
99 #elif EMULATE_CAS
101 
102  enterLock(a);
103  if (a->value == oldval) {
104  a->value = newval;
105  retval = SDL_TRUE;
106  }
107  leaveLock(a);
108 
109  return retval;
110 #else
111  #error Please define your platform.
112 #endif
113 }
114 
115 SDL_bool
116 SDL_AtomicCASPtr(void **a, void *oldval, void *newval)
117 {
118 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
119  return (_InterlockedCompareExchange((long*)a, (long)newval, (long)oldval) == (long)oldval);
120 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
121  return (_InterlockedCompareExchangePointer(a, newval, oldval) == oldval);
122 #elif defined(__MACOSX__) && defined(__LP64__) /* !!! FIXME: should we favor gcc atomics? */
123  return (SDL_bool) OSAtomicCompareAndSwap64Barrier((int64_t)oldval, (int64_t)newval, (int64_t*) a);
124 #elif defined(__MACOSX__) && !defined(__LP64__) /* !!! FIXME: should we favor gcc atomics? */
125  return (SDL_bool) OSAtomicCompareAndSwap32Barrier((int32_t)oldval, (int32_t)newval, (int32_t*) a);
126 #elif defined(HAVE_GCC_ATOMICS)
127  return __sync_bool_compare_and_swap(a, oldval, newval);
128 #elif defined(__SOLARIS__)
129  return (SDL_bool) (atomic_cas_ptr(a, oldval, newval) == oldval);
130 #elif EMULATE_CAS
132 
133  enterLock(a);
134  if (*a == oldval) {
135  *a = newval;
136  retval = SDL_TRUE;
137  }
138  leaveLock(a);
139 
140  return retval;
141 #else
142  #error Please define your platform.
143 #endif
144 }
145 
146 int
148 {
149 #ifdef HAVE_MSC_ATOMICS
150  return _InterlockedExchange((long*)&a->value, v);
151 #elif defined(HAVE_GCC_ATOMICS)
152  return __sync_lock_test_and_set(&a->value, v);
153 #elif defined(__SOLARIS__) && defined(_LP64)
154  return (int) atomic_swap_64((volatile uint64_t*)&a->value, (uint64_t)v);
155 #elif defined(__SOLARIS__) && !defined(_LP64)
156  return (int) atomic_swap_32((volatile uint32_t*)&a->value, (uint32_t)v);
157 #else
158  int value;
159  do {
160  value = a->value;
161  } while (!SDL_AtomicCAS(a, value, v));
162  return value;
163 #endif
164 }
165 
166 void*
167 SDL_AtomicSetPtr(void **a, void *v)
168 {
169 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
170  return (void *) _InterlockedExchange((long *)a, (long) v);
171 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
172  return _InterlockedExchangePointer(a, v);
173 #elif defined(HAVE_GCC_ATOMICS)
174  return __sync_lock_test_and_set(a, v);
175 #elif defined(__SOLARIS__)
176  return atomic_swap_ptr(a, v);
177 #else
178  void *value;
179  do {
180  value = *a;
181  } while (!SDL_AtomicCASPtr(a, value, v));
182  return value;
183 #endif
184 }
185 
186 int
188 {
189 #ifdef HAVE_MSC_ATOMICS
190  return _InterlockedExchangeAdd((long*)&a->value, v);
191 #elif defined(HAVE_GCC_ATOMICS)
192  return __sync_fetch_and_add(&a->value, v);
193 #elif defined(__SOLARIS__)
194  int pv = a->value;
195  membar_consumer();
196 #if defined(_LP64)
197  atomic_add_64((volatile uint64_t*)&a->value, v);
198 #elif !defined(_LP64)
199  atomic_add_32((volatile uint32_t*)&a->value, v);
200 #endif
201  return pv;
202 #else
203  int value;
204  do {
205  value = a->value;
206  } while (!SDL_AtomicCAS(a, value, (value + v)));
207  return value;
208 #endif
209 }
210 
211 int
213 {
214  int value;
215  do {
216  value = a->value;
217  } while (!SDL_AtomicCAS(a, value, value));
218  return value;
219 }
220 
221 void *
223 {
224  void *value;
225  do {
226  value = *a;
227  } while (!SDL_AtomicCASPtr(a, value, value));
228  return value;
229 }
230 
231 #ifdef __thumb__
232 #if defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6T2__) || defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__)
233 __asm__(
234 " .align 2\n"
235 " .globl _SDL_MemoryBarrierRelease\n"
236 " .globl _SDL_MemoryBarrierAcquire\n"
237 "_SDL_MemoryBarrierRelease:\n"
238 "_SDL_MemoryBarrierAcquire:\n"
239 " mov r0, #0\n"
240 " mcr p15, 0, r0, c7, c10, 5\n"
241 " bx lr\n"
242 );
243 #endif
244 #endif
245 
246 /* vi: set ts=4 sw=4 expandtab: */
void * SDL_AtomicGetPtr(void **a)
Get the value of a pointer atomically.
Definition: SDL_atomic.c:222
#define SDL_AtomicLock
signed int int32_t
A type representing an atomic integer value. It is a struct so people don&#39;t accidentally use numeric ...
Definition: SDL_atomic.h:189
unsigned long long uint64_t
int SDL_AtomicGet(SDL_atomic_t *a)
Get the value of an atomic variable.
Definition: SDL_atomic.c:212
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:116
#define SDL_AtomicUnlock
const GLdouble * v
Definition: SDL_opengl.h:2057
SDL_bool retval
GLsizei const GLfloat * value
void * SDL_AtomicSetPtr(void **a, void *v)
Set a pointer to a value atomically.
Definition: SDL_atomic.c:167
static SDL_INLINE void leaveLock(void *a)
Definition: SDL_atomic.c:77
int SDL_AtomicSet(SDL_atomic_t *a, int v)
Set an atomic variable to a value.
Definition: SDL_atomic.c:147
static SDL_INLINE void enterLock(void *a)
Definition: SDL_atomic.c:69
unsigned int uintptr_t
GLuint index
SDL_bool
Definition: SDL_stdinc.h:130
unsigned int uint32_t
int SDL_AtomicAdd(SDL_atomic_t *a, int v)
Add to an atomic variable.
Definition: SDL_atomic.c:187
#define SDL_INLINE
Definition: begin_code.h:120
static SDL_SpinLock locks[32]
Definition: SDL_atomic.c:66
int SDL_SpinLock
Definition: SDL_atomic.h:89
GLboolean GLboolean GLboolean GLboolean 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.
Definition: SDL_atomic.c:87
signed long long int64_t