src/atomic/SDL_spinlock.c
author Ryan C. Gordon
Mon, 01 Jan 2018 19:16:51 -0500
changeset 11803 454f6dc9cb85
parent 11318 06fd8421e8f6
child 11811 5d94cb6b24d3
permissions -rw-r--r--
windows: Remove references to GetVersionExA (thanks, Andrew Pilley!).

"GetVersionExA is deprecated in windows 8.1 and above's SDK, causing a warning
when building against the win10 SDK. Attached patch cleans up the usage for a
warning-free build.

GetVersionExA was being used to test to see if SDL was running on win9x or
winnt. A quick chat with Ryan on twitter suggested that SDL doesn't
officially support win9x anymore, so the call to this can be outright removed.

As an aside, replacing the call to GetVersionExA with VerifyVersionInfoA (the
recommended path) would have been pointless, as VerifyVersionInfoA only
supports VER_PLATFORM_WIN32_NT and doesn't officially support any other value
for dwPlatformId currently. (And it's probable that win9x SDKs didn't have
VerifyVersionInfo* in them anyway.)"

Fixes Bugzilla #4019.
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2017 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_internal.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 #if !defined(HAVE_GCC_ATOMICS) && defined(__SOLARIS__)
    32 #include <atomic.h>
    33 #endif
    34 
    35 #if defined(__WATCOMC__) && defined(__386__)
    36 SDL_COMPILE_TIME_ASSERT(locksize, 4==sizeof(SDL_SpinLock));
    37 extern _inline int _SDL_xchg_watcom(volatile int *a, int v);
    38 #pragma aux _SDL_xchg_watcom = \
    39   "xchg [ecx], eax" \
    40   parm [ecx] [eax] \
    41   value [eax] \
    42   modify exact [eax];
    43 #endif /* __WATCOMC__ && __386__ */
    44 
    45 /* This function is where all the magic happens... */
    46 SDL_bool
    47 SDL_AtomicTryLock(SDL_SpinLock *lock)
    48 {
    49 #if SDL_ATOMIC_DISABLED
    50     /* Terrible terrible damage */
    51     static SDL_mutex *_spinlock_mutex;
    52 
    53     if (!_spinlock_mutex) {
    54         /* Race condition on first lock... */
    55         _spinlock_mutex = SDL_CreateMutex();
    56     }
    57     SDL_LockMutex(_spinlock_mutex);
    58     if (*lock == 0) {
    59         *lock = 1;
    60         SDL_UnlockMutex(_spinlock_mutex);
    61         return SDL_TRUE;
    62     } else {
    63         SDL_UnlockMutex(_spinlock_mutex);
    64         return SDL_FALSE;
    65     }
    66 
    67 #elif defined(_MSC_VER)
    68     SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
    69     return (InterlockedExchange((long*)lock, 1) == 0);
    70 
    71 #elif defined(__WATCOMC__) && defined(__386__)
    72     return _SDL_xchg_watcom(lock, 1) == 0;
    73 
    74 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
    75     return (__sync_lock_test_and_set(lock, 1) == 0);
    76 
    77 #elif defined(__GNUC__) && defined(__arm__) && \
    78         (defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
    79          defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__) || \
    80          defined(__ARM_ARCH_5TEJ__))
    81     int result;
    82     __asm__ __volatile__ (
    83         "swp %0, %1, [%2]\n"
    84         : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
    85     return (result == 0);
    86 
    87 #elif defined(__GNUC__) && defined(__arm__)
    88     int result;
    89     __asm__ __volatile__ (
    90         "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"
    91         : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
    92     return (result == 0);
    93 
    94 #elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
    95     int result;
    96     __asm__ __volatile__(
    97         "lock ; xchgl %0, (%1)\n"
    98         : "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
    99     return (result == 0);
   100 
   101 #elif defined(__MACOSX__) || defined(__IPHONEOS__)
   102     /* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
   103     return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
   104 
   105 #elif defined(__SOLARIS__) && defined(_LP64)
   106     /* Used for Solaris with non-gcc compilers. */
   107     return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)lock, 0, 1) == 0);
   108 
   109 #elif defined(__SOLARIS__) && !defined(_LP64)
   110     /* Used for Solaris with non-gcc compilers. */
   111     return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)lock, 0, 1) == 0);
   112 
   113 #else
   114 #error Please implement for your platform.
   115     return SDL_FALSE;
   116 #endif
   117 }
   118 
   119 void
   120 SDL_AtomicLock(SDL_SpinLock *lock)
   121 {
   122     /* FIXME: Should we have an eventual timeout? */
   123     while (!SDL_AtomicTryLock(lock)) {
   124         SDL_Delay(0);
   125     }
   126 }
   127 
   128 void
   129 SDL_AtomicUnlock(SDL_SpinLock *lock)
   130 {
   131 #if defined(_MSC_VER)
   132     _ReadWriteBarrier();
   133     *lock = 0;
   134 
   135 #elif defined(__WATCOMC__) && defined(__386__)
   136     SDL_CompilerBarrier ();
   137     *lock = 0;
   138 
   139 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
   140     __sync_lock_release(lock);
   141 
   142 #elif defined(__SOLARIS__)
   143     /* Used for Solaris when not using gcc. */
   144     *lock = 0;
   145     membar_producer();
   146 
   147 #else
   148     *lock = 0;
   149 #endif
   150 }
   151 
   152 /* vi: set ts=4 sw=4 expandtab: */