src/atomic/SDL_spinlock.c
author Ozkan Sezer <sezeroz@gmail.com>
Thu, 27 Sep 2018 11:55:02 +0300
changeset 12241 f72836cfb92b
parent 12045 bac108d0cd86
child 12503 806492103856
permissions -rw-r--r--
SDL_atomic.c, SDL_spinlock.c: use lock prefix with xchg in Watcom asm.
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2018 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(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
    36 #include <xmmintrin.h>
    37 #endif
    38 
    39 #if defined(__WATCOMC__) && defined(__386__)
    40 SDL_COMPILE_TIME_ASSERT(locksize, 4==sizeof(SDL_SpinLock));
    41 extern _inline int _SDL_xchg_watcom(volatile int *a, int v);
    42 #pragma aux _SDL_xchg_watcom = \
    43   "lock xchg [ecx], eax" \
    44   parm [ecx] [eax] \
    45   value [eax] \
    46   modify exact [eax];
    47 #endif /* __WATCOMC__ && __386__ */
    48 
    49 /* This function is where all the magic happens... */
    50 SDL_bool
    51 SDL_AtomicTryLock(SDL_SpinLock *lock)
    52 {
    53 #if SDL_ATOMIC_DISABLED
    54     /* Terrible terrible damage */
    55     static SDL_mutex *_spinlock_mutex;
    56 
    57     if (!_spinlock_mutex) {
    58         /* Race condition on first lock... */
    59         _spinlock_mutex = SDL_CreateMutex();
    60     }
    61     SDL_LockMutex(_spinlock_mutex);
    62     if (*lock == 0) {
    63         *lock = 1;
    64         SDL_UnlockMutex(_spinlock_mutex);
    65         return SDL_TRUE;
    66     } else {
    67         SDL_UnlockMutex(_spinlock_mutex);
    68         return SDL_FALSE;
    69     }
    70 
    71 #elif defined(_MSC_VER)
    72     SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
    73     return (InterlockedExchange((long*)lock, 1) == 0);
    74 
    75 #elif defined(__WATCOMC__) && defined(__386__)
    76     return _SDL_xchg_watcom(lock, 1) == 0;
    77 
    78 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
    79     return (__sync_lock_test_and_set(lock, 1) == 0);
    80 
    81 #elif defined(__GNUC__) && defined(__arm__) && \
    82         (defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
    83          defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__) || \
    84          defined(__ARM_ARCH_5TEJ__))
    85     int result;
    86     __asm__ __volatile__ (
    87         "swp %0, %1, [%2]\n"
    88         : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
    89     return (result == 0);
    90 
    91 #elif defined(__GNUC__) && defined(__arm__)
    92     int result;
    93     __asm__ __volatile__ (
    94         "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"
    95         : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
    96     return (result == 0);
    97 
    98 #elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
    99     int result;
   100     __asm__ __volatile__(
   101         "lock ; xchgl %0, (%1)\n"
   102         : "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
   103     return (result == 0);
   104 
   105 #elif defined(__MACOSX__) || defined(__IPHONEOS__)
   106     /* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
   107     return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
   108 
   109 #elif defined(__SOLARIS__) && defined(_LP64)
   110     /* Used for Solaris with non-gcc compilers. */
   111     return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)lock, 0, 1) == 0);
   112 
   113 #elif defined(__SOLARIS__) && !defined(_LP64)
   114     /* Used for Solaris with non-gcc compilers. */
   115     return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)lock, 0, 1) == 0);
   116 
   117 #else
   118 #error Please implement for your platform.
   119     return SDL_FALSE;
   120 #endif
   121 }
   122 
   123 /* "REP NOP" is PAUSE, coded for tools that don't know it by that name. */
   124 #if (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__))
   125     #define PAUSE_INSTRUCTION() __asm__ __volatile__("pause\n")  /* Some assemblers can't do REP NOP, so go with PAUSE. */
   126 #elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
   127     #define PAUSE_INSTRUCTION() _mm_pause()  /* this is actually "rep nop" and not a SIMD instruction. No inline asm in MSVC x86-64! */
   128 #elif defined(__WATCOMC__) && defined(__386__)
   129     /* watcom assembler rejects PAUSE if CPU < i686, and it refuses REP NOP as an invalid combination. Hardcode the bytes.  */
   130     extern _inline void PAUSE_INSTRUCTION(void);
   131     #pragma aux PAUSE_INSTRUCTION = "db 0f3h,90h"
   132 #else
   133     #define PAUSE_INSTRUCTION()
   134 #endif
   135 
   136 void
   137 SDL_AtomicLock(SDL_SpinLock *lock)
   138 {
   139     int iterations = 0;
   140     /* FIXME: Should we have an eventual timeout? */
   141     while (!SDL_AtomicTryLock(lock)) {
   142         if (iterations < 32) {
   143             iterations++;
   144             PAUSE_INSTRUCTION();
   145         } else {
   146             /* !!! FIXME: this doesn't definitely give up the current timeslice, it does different things on various platforms. */
   147             SDL_Delay(0);
   148         }
   149     }
   150 }
   151 
   152 void
   153 SDL_AtomicUnlock(SDL_SpinLock *lock)
   154 {
   155 #if defined(_MSC_VER)
   156     _ReadWriteBarrier();
   157     *lock = 0;
   158 
   159 #elif defined(__WATCOMC__) && defined(__386__)
   160     SDL_CompilerBarrier ();
   161     *lock = 0;
   162 
   163 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
   164     __sync_lock_release(lock);
   165 
   166 #elif defined(__SOLARIS__)
   167     /* Used for Solaris when not using gcc. */
   168     *lock = 0;
   169     membar_producer();
   170 
   171 #else
   172     *lock = 0;
   173 #endif
   174 }
   175 
   176 /* vi: set ts=4 sw=4 expandtab: */