This repository has been archived by the owner on Feb 11, 2021. It is now read-only.
SDL_spinlock.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2010 Sam Lantinga
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Sam Lantinga
slouken@libsdl.org
*/
#include "SDL_stdinc.h"
#include "SDL_atomic.h"
#include "SDL_timer.h"
27
/* Don't do the check for Visual Studio 2005, it's safe here */
28
#include "../core/windows/SDL_windows.h"
29
30
31
32
33
/* This function is where all the magic happens... */
SDL_bool
SDL_AtomicTryLock(SDL_SpinLock *lock)
{
34
#if defined(_MSC_VER)
35
SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
36
return (InterlockedExchange((long*)lock, 1) == 0);
37
38
39
40
#elif defined(__MACOSX__)
return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
41
#elif defined(HAVE_GCC_ATOMICS) || defined(HAVE_GCC_SYNC_LOCK_TEST_AND_SET)
42
43
44
return (__sync_lock_test_and_set(lock, 1) == 0);
#elif defined(__GNUC__) && defined(__arm__) && defined(__ARM_ARCH_5__)
45
46
47
48
49
int result;
__asm__ __volatile__ (
"swp %0, %1, [%2]\n"
: "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
return (result == 0);
50
51
#elif defined(__GNUC__) && defined(__arm__)
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
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);
#else
/* Need CPU instructions for spinlock here! */
__need_spinlock_implementation__
#endif
}
void
SDL_AtomicLock(SDL_SpinLock *lock)
{
/* FIXME: Should we have an eventual timeout? */
while (!SDL_AtomicTryLock(lock)) {
SDL_Delay(0);
}
}
void
SDL_AtomicUnlock(SDL_SpinLock *lock)
{
76
/* Assuming atomic assignment operation and full memory barrier in lock */
77
78
79
80
*lock = 0;
}
/* vi: set ts=4 sw=4 expandtab: */