src/atomic/SDL_spinlock.c
author Sam Lantinga <slouken@libsdl.org>
Tue, 18 Jan 2011 22:10:37 -0800
changeset 5028 fffb33ae85e8
parent 5015 1bf9e38431ec
child 5069 fd125217f00c
permissions -rw-r--r--
Whoops, good catch from Greg Jandl
     1 /*
     2   SDL - Simple DirectMedia Layer
     3   Copyright (C) 1997-2010 Sam Lantinga
     4 
     5   This library is free software; you can redistribute it and/or
     6   modify it under the terms of the GNU Lesser General Public
     7   License as published by the Free Software Foundation; either
     8   version 2.1 of the License, or (at your option) any later version.
     9 
    10   This library is distributed in the hope that it will be useful,
    11   but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13   Lesser General Public License for more details.
    14 
    15   You should have received a copy of the GNU Lesser General Public
    16   License along with this library; if not, write to the Free Software
    17   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
    18 
    19   Sam Lantinga
    20   slouken@libsdl.org
    21 */
    22 #include "SDL_stdinc.h"
    23 
    24 #include "SDL_atomic.h"
    25 #include "SDL_timer.h"
    26 
    27 
    28 /* This function is where all the magic happens... */
    29 SDL_bool
    30 SDL_AtomicTryLock(SDL_SpinLock *lock)
    31 {
    32 #if defined(_MSC_VER)
    33     SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
    34     return (_InterlockedExchange((long*)lock, 1) == 0);
    35 
    36 #elif defined(__MACOSX__)
    37     return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
    38 
    39 #elif defined(HAVE_GCC_ATOMICS)
    40     return (__sync_lock_test_and_set(lock, 1) == 0);
    41 
    42 #elif defined(__GNUC__) && defined(__arm__) && defined(__ARM_ARCH_5__)
    43     int result;
    44     __asm__ __volatile__ (
    45         "swp %0, %1, [%2]\n"
    46         : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
    47     return (result == 0);
    48 
    49 #elif defined(__GNUC__) && defined(__arm__)
    50     int result;
    51     __asm__ __volatile__ (
    52         "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"
    53         : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
    54     return (result == 0);
    55 
    56 #else
    57     /* Need CPU instructions for spinlock here! */
    58     __need_spinlock_implementation__
    59 #endif
    60 }
    61 
    62 void
    63 SDL_AtomicLock(SDL_SpinLock *lock)
    64 {
    65     /* FIXME: Should we have an eventual timeout? */
    66     while (!SDL_AtomicTryLock(lock)) {
    67         SDL_Delay(0);
    68     }
    69 }
    70 
    71 void
    72 SDL_AtomicUnlock(SDL_SpinLock *lock)
    73 {
    74     /* Assuming atomic assignment operation and full memory barrier in lock */
    75     *lock = 0;
    76 }
    77 
    78 /* vi: set ts=4 sw=4 expandtab: */