src/atomic/SDL_spinlock.c
author Sam Lantinga <slouken@libsdl.org>
Sun, 09 Mar 2014 11:06:11 -0700
changeset 8582 c3e9a2b93517
parent 8536 a2be4a225f91
child 8583 fb2933ca805f
permissions -rw-r--r--
Fixed line endings on WinRT source code
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2013 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_config.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 
    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_LockMutex(_spinlock_mutex);
    45     if (*lock == 0) {
    46         *lock = 1;
    47         SDL_UnlockMutex(_spinlock_mutex);
    48         return SDL_TRUE;
    49     } else {
    50         SDL_UnlockMutex(_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          defined(__ARM_ARCH_5TEJ__))
    65     int result;
    66     __asm__ __volatile__ (
    67         "swp %0, %1, [%2]\n"
    68         : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
    69     return (result == 0);
    70 
    71 #elif defined(__GNUC__) && defined(__arm__)
    72     int result;
    73     __asm__ __volatile__ (
    74         "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"
    75         : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
    76     return (result == 0);
    77 
    78 #elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
    79     int result;
    80     __asm__ __volatile__(
    81         "lock ; xchgl %0, (%1)\n"
    82         : "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
    83     return (result == 0);
    84 
    85 #elif defined(__MACOSX__) || defined(__IPHONEOS__)
    86     /* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
    87     return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
    88 
    89 #elif HAVE_PTHREAD_SPINLOCK
    90     /* pthread instructions */
    91     return (pthread_spin_trylock(lock) == 0);
    92 
    93 #else
    94 #error Please implement for your platform.
    95     return SDL_FALSE;
    96 #endif
    97 }
    98 
    99 void
   100 SDL_AtomicLock(SDL_SpinLock *lock)
   101 {
   102     /* FIXME: Should we have an eventual timeout? */
   103     while (!SDL_AtomicTryLock(lock)) {
   104         SDL_Delay(0);
   105     }
   106 }
   107 
   108 void
   109 SDL_AtomicUnlock(SDL_SpinLock *lock)
   110 {
   111 #if defined(_MSC_VER)
   112     _ReadWriteBarrier();
   113     *lock = 0;
   114 
   115 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
   116     __sync_lock_release(lock);
   117 
   118 #elif HAVE_PTHREAD_SPINLOCK
   119     pthread_spin_unlock(lock);
   120 
   121 #else
   122     *lock = 0;
   123 #endif
   124 }
   125 
   126 /* vi: set ts=4 sw=4 expandtab: */