src/atomic/SDL_spinlock.c
author Ryan C. Gordon <icculus@icculus.org>
Sun, 18 Sep 2011 03:19:41 -0400
changeset 5957 9a2b091abb2c
parent 5956 c7aebf1841ca
child 5998 e9b9ef14aef4
permissions -rw-r--r--
Implemented x86 and x86-64 spinlock inline asm.

Favor it over Mac OS X API for Intel systems (but not GCC atomic intrinsics).

This might get us a little further on Cygwin builds, too.
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2011 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_stdinc.h"
    22 
    23 #include "SDL_atomic.h"
    24 #include "SDL_mutex.h"
    25 #include "SDL_timer.h"
    26 
    27 /* Don't do the check for Visual Studio 2005, it's safe here */
    28 #ifdef __WIN32__
    29 #include "../core/windows/SDL_windows.h"
    30 #endif
    31 
    32 /* This function is where all the magic happens... */
    33 SDL_bool
    34 SDL_AtomicTryLock(SDL_SpinLock *lock)
    35 {
    36 #if SDL_ATOMIC_DISABLED
    37     /* Terrible terrible damage */
    38     static SDL_mutex *_spinlock_mutex;
    39 
    40     if (!_spinlock_mutex) {
    41         /* Race condition on first lock... */
    42         _spinlock_mutex = SDL_CreateMutex();
    43     }
    44     SDL_mutexP(_spinlock_mutex);
    45     if (*lock == 0) {
    46         *lock = 1;
    47         SDL_mutexV(_spinlock_mutex);
    48         return SDL_TRUE;
    49     } else {
    50         SDL_mutexV(_spinlock_mutex);
    51         return SDL_FALSE;
    52     }
    53 
    54 #elif defined(_MSC_VER)
    55     SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
    56     return (InterlockedExchange((long*)lock, 1) == 0);
    57 
    58 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
    59     return (__sync_lock_test_and_set(lock, 1) == 0);
    60 
    61 #elif defined(__GNUC__) && defined(__arm__) && \
    62         (defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
    63          defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__))
    64     int result;
    65     __asm__ __volatile__ (
    66         "swp %0, %1, [%2]\n"
    67         : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
    68     return (result == 0);
    69 
    70 #elif defined(__GNUC__) && defined(__arm__)
    71     int result;
    72     __asm__ __volatile__ (
    73         "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"
    74         : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
    75     return (result == 0);
    76 
    77 #elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
    78 	int result;
    79 	__asm__ __volatile__(
    80         "lock ; xchgl %0, (%1)\n"
    81         : "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
    82 	return (result == 0);
    83 
    84 #elif defined(__MACOSX__)
    85     /* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
    86     return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
    87 
    88 #elif HAVE_PTHREAD_SPINLOCK
    89     /* pthread instructions */
    90     return (pthread_spin_trylock(lock) == 0);
    91 
    92 #else
    93 #error Please implement for your platform.
    94     return SDL_FALSE;
    95 #endif
    96 }
    97 
    98 void
    99 SDL_AtomicLock(SDL_SpinLock *lock)
   100 {
   101     /* FIXME: Should we have an eventual timeout? */
   102     while (!SDL_AtomicTryLock(lock)) {
   103         SDL_Delay(0);
   104     }
   105 }
   106 
   107 void
   108 SDL_AtomicUnlock(SDL_SpinLock *lock)
   109 {
   110 #if defined(_MSC_VER)
   111     _ReadWriteBarrier();
   112     *lock = 0;
   113 
   114 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
   115     __sync_lock_release(lock);
   116     
   117 #elif HAVE_PTHREAD_SPINLOCK
   118     pthread_spin_unlock(lock);
   119 	
   120 #else
   121     *lock = 0;
   122 #endif
   123 }
   124 
   125 /* vi: set ts=4 sw=4 expandtab: */