SDL  2.0
SDL_spinlock.c
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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 #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 /* This function is where all the magic happens... */
38 {
39 #if SDL_ATOMIC_DISABLED
40  /* Terrible terrible damage */
41  static SDL_mutex *_spinlock_mutex;
42 
43  if (!_spinlock_mutex) {
44  /* Race condition on first lock... */
45  _spinlock_mutex = SDL_CreateMutex();
46  }
47  SDL_LockMutex(_spinlock_mutex);
48  if (*lock == 0) {
49  *lock = 1;
50  SDL_UnlockMutex(_spinlock_mutex);
51  return SDL_TRUE;
52  } else {
53  SDL_UnlockMutex(_spinlock_mutex);
54  return SDL_FALSE;
55  }
56 
57 #elif defined(_MSC_VER)
58  SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
59  return (InterlockedExchange((long*)lock, 1) == 0);
60 
61 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
62  return (__sync_lock_test_and_set(lock, 1) == 0);
63 
64 #elif defined(__GNUC__) && defined(__arm__) && \
65  (defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
66  defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__) || \
67  defined(__ARM_ARCH_5TEJ__))
68  int result;
69  __asm__ __volatile__ (
70  "swp %0, %1, [%2]\n"
71  : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
72  return (result == 0);
73 
74 #elif defined(__GNUC__) && defined(__arm__)
75  int result;
76  __asm__ __volatile__ (
77  "ldrex %0, [%2]\nteq %0, #0\nstrexeq %0, %1, [%2]"
78  : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
79  return (result == 0);
80 
81 #elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
82  int result;
83  __asm__ __volatile__(
84  "lock ; xchgl %0, (%1)\n"
85  : "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
86  return (result == 0);
87 
88 #elif defined(__MACOSX__) || defined(__IPHONEOS__)
89  /* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
90  return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
91 
92 #elif defined(__SOLARIS__) && defined(_LP64)
93  /* Used for Solaris with non-gcc compilers. */
94  return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)lock, 0, 1) == 0);
95 
96 #elif defined(__SOLARIS__) && !defined(_LP64)
97  /* Used for Solaris with non-gcc compilers. */
98  return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)lock, 0, 1) == 0);
99 
100 #else
101 #error Please implement for your platform.
102  return SDL_FALSE;
103 #endif
104 }
105 
106 void
108 {
109  /* FIXME: Should we have an eventual timeout? */
110  while (!SDL_AtomicTryLock(lock)) {
111  SDL_Delay(0);
112  }
113 }
114 
115 void
117 {
118 #if defined(_MSC_VER)
119  _ReadWriteBarrier();
120  *lock = 0;
121 
122 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
123  __sync_lock_release(lock);
124 
125 #elif defined(__SOLARIS__)
126  /* Used for Solaris when not using gcc. */
127  *lock = 0;
128  membar_producer();
129 
130 #else
131  *lock = 0;
132 #endif
133 }
134 
135 /* vi: set ts=4 sw=4 expandtab: */
#define SDL_LockMutex
GLuint64EXT * result
void SDL_AtomicLock(SDL_SpinLock *lock)
Lock a spin lock by setting it to a non-zero value.
Definition: SDL_spinlock.c:107
void SDL_AtomicUnlock(SDL_SpinLock *lock)
Unlock a spin lock by setting it to 0. Always returns immediately.
Definition: SDL_spinlock.c:116
#define SDL_CreateMutex
unsigned long long uint64_t
#define SDL_Delay
SDL_bool
Definition: SDL_stdinc.h:130
unsigned int uint32_t
SDL_mutex * lock
Definition: SDL_events.c:75
SDL_COMPILE_TIME_ASSERT(size, CountTo >0)
#define SDL_UnlockMutex
int SDL_SpinLock
Definition: SDL_atomic.h:89
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:37