SDL_spinlock.c
1
2
/*
Simple DirectMedia Layer
3
Copyright (C) 1997-2019 Sam Lantinga <slouken@libsdl.org>
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "../SDL_internal.h"
#if defined(__WIN32__) || defined(__WINRT__)
#include "../core/windows/SDL_windows.h"
#endif
#include "SDL_atomic.h"
#include "SDL_mutex.h"
#include "SDL_timer.h"
#if !defined(HAVE_GCC_ATOMICS) && defined(__SOLARIS__)
#include <atomic.h>
#endif
35
36
37
38
#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
#include <xmmintrin.h>
#endif
39
40
41
42
#if defined(__WATCOMC__) && defined(__386__)
SDL_COMPILE_TIME_ASSERT(locksize, 4==sizeof(SDL_SpinLock));
extern _inline int _SDL_xchg_watcom(volatile int *a, int v);
#pragma aux _SDL_xchg_watcom = \
43
"lock xchg [ecx], eax" \
44
45
46
47
48
parm [ecx] [eax] \
value [eax] \
modify exact [eax];
#endif /* __WATCOMC__ && __386__ */
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
/* This function is where all the magic happens... */
SDL_bool
SDL_AtomicTryLock(SDL_SpinLock *lock)
{
#if SDL_ATOMIC_DISABLED
/* Terrible terrible damage */
static SDL_mutex *_spinlock_mutex;
if (!_spinlock_mutex) {
/* Race condition on first lock... */
_spinlock_mutex = SDL_CreateMutex();
}
SDL_LockMutex(_spinlock_mutex);
if (*lock == 0) {
*lock = 1;
SDL_UnlockMutex(_spinlock_mutex);
return SDL_TRUE;
} else {
SDL_UnlockMutex(_spinlock_mutex);
return SDL_FALSE;
}
#elif defined(_MSC_VER)
SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
return (InterlockedExchange((long*)lock, 1) == 0);
75
76
77
#elif defined(__WATCOMC__) && defined(__386__)
return _SDL_xchg_watcom(lock, 1) == 0;
78
79
80
81
#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
return (__sync_lock_test_and_set(lock, 1) == 0);
#elif defined(__GNUC__) && defined(__arm__) && \
82
83
(defined(__ARM_ARCH_3__) || defined(__ARM_ARCH_3M__) || \
defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__) || \
defined(__ARM_ARCH_5TEJ__))
int result;
__asm__ __volatile__ (
"swp %0, %1, [%2]\n"
: "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
return (result == 0);
#elif defined(__GNUC__) && defined(__arm__)
int result;
__asm__ __volatile__ (
"ldrex %0, [%2]\nteq %0, #0\nstrexeq %0, %1, [%2]"
: "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
return (result == 0);
#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
int result;
__asm__ __volatile__(
"lock ; xchgl %0, (%1)\n"
: "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
return (result == 0);
#elif defined(__MACOSX__) || defined(__IPHONEOS__)
/* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
#elif defined(__SOLARIS__) && defined(_LP64)
/* Used for Solaris with non-gcc compilers. */
return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)lock, 0, 1) == 0);
#elif defined(__SOLARIS__) && !defined(_LP64)
/* Used for Solaris with non-gcc compilers. */
return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)lock, 0, 1) == 0);
#else
#error Please implement for your platform.
return SDL_FALSE;
#endif
}
124
125
/* "REP NOP" is PAUSE, coded for tools that don't know it by that name. */
#if (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__))
126
#define PAUSE_INSTRUCTION() __asm__ __volatile__("pause\n") /* Some assemblers can't do REP NOP, so go with PAUSE. */
127
#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
128
#define PAUSE_INSTRUCTION() _mm_pause() /* this is actually "rep nop" and not a SIMD instruction. No inline asm in MSVC x86-64! */
129
#elif defined(__WATCOMC__) && defined(__386__)
130
/* watcom assembler rejects PAUSE if CPU < i686, and it refuses REP NOP as an invalid combination. Hardcode the bytes. */
131
extern _inline void PAUSE_INSTRUCTION(void);
132
#pragma aux PAUSE_INSTRUCTION = "db 0f3h,90h"
133
134
135
136
#else
#define PAUSE_INSTRUCTION()
#endif
137
138
139
void
SDL_AtomicLock(SDL_SpinLock *lock)
{
140
int iterations = 0;
141
142
/* FIXME: Should we have an eventual timeout? */
while (!SDL_AtomicTryLock(lock)) {
143
144
145
146
147
148
149
if (iterations < 32) {
iterations++;
PAUSE_INSTRUCTION();
} else {
/* !!! FIXME: this doesn't definitely give up the current timeslice, it does different things on various platforms. */
SDL_Delay(0);
}
150
151
152
153
154
155
156
157
158
159
}
}
void
SDL_AtomicUnlock(SDL_SpinLock *lock)
{
#if defined(_MSC_VER)
_ReadWriteBarrier();
*lock = 0;
160
161
162
163
#elif defined(__WATCOMC__) && defined(__386__)
SDL_CompilerBarrier ();
*lock = 0;
164
165
166
167
168
169
170
171
172
173
174
175
176
177
#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
__sync_lock_release(lock);
#elif defined(__SOLARIS__)
/* Used for Solaris when not using gcc. */
*lock = 0;
membar_producer();
#else
*lock = 0;
#endif
}
/* vi: set ts=4 sw=4 expandtab: */