SDL 2.0
SDL_spinlock.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#if defined(__WIN32__) || defined(__WINRT__)
24#include "../core/windows/SDL_windows.h"
25#endif
26
27#include "SDL_atomic.h"
28#include "SDL_mutex.h"
29#include "SDL_timer.h"
30
31#if !defined(HAVE_GCC_ATOMICS) && defined(__SOLARIS__)
32#include <atomic.h>
33#endif
34
35#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
36#include <xmmintrin.h>
37#endif
38
39#if defined(__WATCOMC__) && defined(__386__)
40SDL_COMPILE_TIME_ASSERT(locksize, 4==sizeof(SDL_SpinLock));
41extern _inline int _SDL_xchg_watcom(volatile int *a, int v);
42#pragma aux _SDL_xchg_watcom = \
43 "lock xchg [ecx], eax" \
44 parm [ecx] [eax] \
45 value [eax] \
46 modify exact [eax];
47#endif /* __WATCOMC__ && __386__ */
48
49/* This function is where all the magic happens... */
52{
53#if SDL_ATOMIC_DISABLED
54 /* Terrible terrible damage */
55 static SDL_mutex *_spinlock_mutex;
56
57 if (!_spinlock_mutex) {
58 /* Race condition on first lock... */
59 _spinlock_mutex = SDL_CreateMutex();
60 }
61 SDL_LockMutex(_spinlock_mutex);
62 if (*lock == 0) {
63 *lock = 1;
64 SDL_UnlockMutex(_spinlock_mutex);
65 return SDL_TRUE;
66 } else {
67 SDL_UnlockMutex(_spinlock_mutex);
68 return SDL_FALSE;
69 }
70
71#elif defined(_MSC_VER)
72 SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
73 return (InterlockedExchange((long*)lock, 1) == 0);
74
75#elif defined(__WATCOMC__) && defined(__386__)
76 return _SDL_xchg_watcom(lock, 1) == 0;
77
78#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
79 return (__sync_lock_test_and_set(lock, 1) == 0);
80
81#elif defined(__GNUC__) && defined(__arm__) && \
82 (defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
83 defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__) || \
84 defined(__ARM_ARCH_5TEJ__))
85 int result;
86 __asm__ __volatile__ (
87 "swp %0, %1, [%2]\n"
88 : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
89 return (result == 0);
90
91#elif defined(__GNUC__) && defined(__arm__)
92 int result;
93 __asm__ __volatile__ (
94 "ldrex %0, [%2]\nteq %0, #0\nstrexeq %0, %1, [%2]"
95 : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
96 return (result == 0);
97
98#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
99 int result;
100 __asm__ __volatile__(
101 "lock ; xchgl %0, (%1)\n"
102 : "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
103 return (result == 0);
104
105#elif defined(__MACOSX__) || defined(__IPHONEOS__)
106 /* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
107 return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
108
109#elif defined(__SOLARIS__) && defined(_LP64)
110 /* Used for Solaris with non-gcc compilers. */
111 return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)lock, 0, 1) == 0);
112
113#elif defined(__SOLARIS__) && !defined(_LP64)
114 /* Used for Solaris with non-gcc compilers. */
115 return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)lock, 0, 1) == 0);
116
117#else
118#error Please implement for your platform.
119 return SDL_FALSE;
120#endif
121}
122
123/* "REP NOP" is PAUSE, coded for tools that don't know it by that name. */
124#if (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__))
125 #define PAUSE_INSTRUCTION() __asm__ __volatile__("pause\n") /* Some assemblers can't do REP NOP, so go with PAUSE. */
126#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
127 #define PAUSE_INSTRUCTION() _mm_pause() /* this is actually "rep nop" and not a SIMD instruction. No inline asm in MSVC x86-64! */
128#elif defined(__WATCOMC__) && defined(__386__)
129 /* watcom assembler rejects PAUSE if CPU < i686, and it refuses REP NOP as an invalid combination. Hardcode the bytes. */
130 extern _inline void PAUSE_INSTRUCTION(void);
131 #pragma aux PAUSE_INSTRUCTION = "db 0f3h,90h"
132#else
133 #define PAUSE_INSTRUCTION()
134#endif
135
136void
138{
139 int iterations = 0;
140 /* FIXME: Should we have an eventual timeout? */
141 while (!SDL_AtomicTryLock(lock)) {
142 if (iterations < 32) {
143 iterations++;
145 } else {
146 /* !!! FIXME: this doesn't definitely give up the current timeslice, it does different things on various platforms. */
147 SDL_Delay(0);
148 }
149 }
150}
151
152void
154{
155#if defined(_MSC_VER)
156 _ReadWriteBarrier();
157 *lock = 0;
158
159#elif defined(__WATCOMC__) && defined(__386__)
161 *lock = 0;
162
163#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
164 __sync_lock_release(lock);
165
166#elif defined(__SOLARIS__)
167 /* Used for Solaris when not using gcc. */
168 *lock = 0;
169 membar_producer();
170
171#else
172 *lock = 0;
173#endif
174}
175
176/* vi: set ts=4 sw=4 expandtab: */
#define SDL_CompilerBarrier()
Definition: SDL_atomic.h:132
int SDL_SpinLock
Definition: SDL_atomic.h:89
unsigned int uint32_t
unsigned long long uint64_t
#define SDL_LockMutex
#define SDL_CreateMutex
#define SDL_Delay
#define SDL_UnlockMutex
SDL_mutex * lock
Definition: SDL_events.c:76
const GLdouble * v
Definition: SDL_opengl.h:2064
GLuint64EXT * result
GLboolean GLboolean GLboolean GLboolean a
SDL_bool SDL_AtomicTryLock(SDL_SpinLock *lock)
Try to lock a spin lock by setting it to a non-zero value.
Definition: SDL_spinlock.c:51
#define PAUSE_INSTRUCTION()
Definition: SDL_spinlock.c:133
void SDL_AtomicUnlock(SDL_SpinLock *lock)
Unlock a spin lock by setting it to 0. Always returns immediately.
Definition: SDL_spinlock.c:153
void SDL_AtomicLock(SDL_SpinLock *lock)
Lock a spin lock by setting it to a non-zero value.
Definition: SDL_spinlock.c:137
SDL_bool
Definition: SDL_stdinc.h:162
@ SDL_TRUE
Definition: SDL_stdinc.h:164
@ SDL_FALSE
Definition: SDL_stdinc.h:163
#define SDL_COMPILE_TIME_ASSERT(name, x)
Definition: SDL_stdinc.h:312
static int iterations
Definition: testsprite2.c:45