SDL_spinlock.c File Reference

#include "../SDL_internal.h"
#include "SDL_atomic.h"
#include "SDL_mutex.h"
#include "SDL_timer.h"

Include dependency graph for SDL_spinlock.c:

Go to the source code of this file.

Macros
#define	PAUSE_INSTRUCTION()

Functions
SDL_bool	SDL_AtomicTryLock (SDL_SpinLock *lock)
	Try to lock a spin lock by setting it to a non-zero value.
void	SDL_AtomicLock (SDL_SpinLock *lock)
	Lock a spin lock by setting it to a non-zero value.
void	SDL_AtomicUnlock (SDL_SpinLock *lock)
	Unlock a spin lock by setting it to 0. Always returns immediately.

Macro Definition Documentation

#define PAUSE_INSTRUCTION

(

)

Definition at line 133 of file SDL_spinlock.c.

Referenced by SDL_AtomicLock().

Function Documentation

void SDL_AtomicLock

(

SDL_SpinLock *

lock

)

Lock a spin lock by setting it to a non-zero value.

Parameters

lock	Points to the lock.

Definition at line 137 of file SDL_spinlock.c.

References iterations, PAUSE_INSTRUCTION, SDL_AtomicTryLock, and SDL_Delay.

{
    int iterations = 0;
    /* FIXME: Should we have an eventual timeout? */
    while (!SDL_AtomicTryLock(lock)) {
        if (iterations < 32) {
            iterations++;
            PAUSE_INSTRUCTION();
        } else {
            /* !!! FIXME: this doesn't definitely give up the current timeslice, it does different things on various platforms. */
            SDL_Delay(0);
        }
    }
}

SDL_bool SDL_AtomicTryLock

(

SDL_SpinLock *

lock

)

Try to lock a spin lock by setting it to a non-zero value.

Parameters

lock	Points to the lock.

Returns

SDL_TRUE if the lock succeeded, SDL_FALSE if the lock is already held.

Definition at line 51 of file SDL_spinlock.c.

References lock, SDL_COMPILE_TIME_ASSERT, SDL_CreateMutex, SDL_FALSE, SDL_LockMutex, SDL_TRUE, and SDL_UnlockMutex.

{
#if SDL_ATOMIC_DISABLED
    /* Terrible terrible damage */
    static SDL_mutex *_spinlock_mutex;

    if (!_spinlock_mutex) {
        /* Race condition on first lock... */
        _spinlock_mutex = SDL_CreateMutex();
    }
    SDL_LockMutex(_spinlock_mutex);
    if (*lock == 0) {
        *lock = 1;
        SDL_UnlockMutex(_spinlock_mutex);
        return SDL_TRUE;
    } else {
        SDL_UnlockMutex(_spinlock_mutex);
        return SDL_FALSE;
    }

#elif defined(_MSC_VER)
    SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
    return (InterlockedExchange((long*)lock, 1) == 0);

#elif defined(__WATCOMC__) && defined(__386__)
    return _SDL_xchg_watcom(lock, 1) == 0;

#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
    return (__sync_lock_test_and_set(lock, 1) == 0);

#elif defined(__GNUC__) && defined(__arm__) && \
        (defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
         defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__) || \
         defined(__ARM_ARCH_5TEJ__))
    int result;
    __asm__ __volatile__ (
        "swp %0, %1, [%2]\n"
        : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
    return (result == 0);

#elif defined(__GNUC__) && defined(__arm__)
    int result;
    __asm__ __volatile__ (
        "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"
        : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
    return (result == 0);

#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
    int result;
    __asm__ __volatile__(
        "lock ; xchgl %0, (%1)\n"
        : "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
    return (result == 0);

#elif defined(__MACOSX__) || defined(__IPHONEOS__)
    /* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
    return OSAtomicCompareAndSwap32Barrier(0, 1, lock);

#elif defined(__SOLARIS__) && defined(_LP64)
    /* Used for Solaris with non-gcc compilers. */
    return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)lock, 0, 1) == 0);

#elif defined(__SOLARIS__) && !defined(_LP64)
    /* Used for Solaris with non-gcc compilers. */
    return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)lock, 0, 1) == 0);

#else
#error Please implement for your platform.
    return SDL_FALSE;
#endif
}

void SDL_AtomicUnlock

(

SDL_SpinLock *

lock

)

Unlock a spin lock by setting it to 0. Always returns immediately.

Parameters

lock	Points to the lock.

Definition at line 153 of file SDL_spinlock.c.

References SDL_CompilerBarrier.

{
#if defined(_MSC_VER)
    _ReadWriteBarrier();
    *lock = 0;

#elif defined(__WATCOMC__) && defined(__386__)
    SDL_CompilerBarrier ();
    *lock = 0;

#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
    __sync_lock_release(lock);

#elif defined(__SOLARIS__)
    /* Used for Solaris when not using gcc. */
    *lock = 0;
    membar_producer();

#else
    *lock = 0;
#endif
}