src/atomic/SDL_spinlock.c
author Nathan Heisey <nathanheisey@gmail.com>
Wed, 22 Jun 2011 10:33:48 +0000
changeset 5557 c1ed57cbfd66
parent 5535 96594ac5fd1a
child 5956 c7aebf1841ca
permissions -rw-r--r--
Implemented pthread spinlocks.
     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 defined(__MACOSX__)
    59     return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
    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     int result;
    68     __asm__ __volatile__ (
    69         "swp %0, %1, [%2]\n"
    70         : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
    71     return (result == 0);
    72 
    73 #elif defined(__GNUC__) && defined(__arm__)
    74     int result;
    75     __asm__ __volatile__ (
    76         "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"
    77         : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
    78     return (result == 0);
    79 
    80 #elif HAVE_PTHREAD_SPINLOCK
    81     /* pthread instructions */
    82     return (pthread_spin_trylock(lock) == 0);
    83 #else	
    84     /* Need CPU instructions for spinlock here! */
    85     __need_spinlock_implementation__
    86 	
    87 #endif
    88 }
    89 
    90 void
    91 SDL_AtomicLock(SDL_SpinLock *lock)
    92 {
    93     /* FIXME: Should we have an eventual timeout? */
    94     while (!SDL_AtomicTryLock(lock)) {
    95         SDL_Delay(0);
    96     }
    97 }
    98 
    99 void
   100 SDL_AtomicUnlock(SDL_SpinLock *lock)
   101 {
   102 #if defined(_MSC_VER)
   103     _ReadWriteBarrier();
   104     *lock = 0;
   105 
   106 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
   107     __sync_lock_release(lock);
   108     
   109 #elif HAVE_PTHREAD_SPINLOCK
   110     pthread_spin_unlock(lock);
   111 	
   112 #else
   113     *lock = 0;
   114 #endif
   115 }
   116 
   117 /* vi: set ts=4 sw=4 expandtab: */