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cpython-withatomic / Python / thread_beos.h

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#include <kernel/OS.h>
#include <support/SupportDefs.h>
#include <errno.h>

/* ----------------------------------------------------------------------
 * Fast locking mechanism described by Benoit Schillings (benoit@be.com)
 * in the Be Developer's Newsletter, Issue #26 (http://www.be.com/).
 */
typedef struct benaphore {
    sem_id _sem;
    int32  _atom;
} benaphore_t;

static status_t benaphore_create( const char *name, benaphore_t *ben );
static status_t benaphore_destroy( benaphore_t *ben );
static status_t benaphore_lock( benaphore_t *ben );
static status_t benaphore_timedlock( benaphore_t *ben, bigtime_t micros );
static status_t benaphore_unlock( benaphore_t *ben );

static status_t benaphore_create( const char *name, benaphore_t *ben )
{
    if( ben != NULL ) {
        ben->_atom = 0;
        ben->_sem = create_sem( 0, name );

        if( ben->_sem < B_NO_ERROR ) {
            return B_BAD_SEM_ID;
        }
    } else {
        return EFAULT;
    }

    return EOK;
}

static status_t benaphore_destroy( benaphore_t *ben )
{
    if( ben->_sem >= B_NO_ERROR ) {
        status_t retval = benaphore_timedlock( ben, 0 );

        if( retval == EOK || retval == EWOULDBLOCK ) {
            status_t del_retval = delete_sem( ben->_sem );

            return del_retval;
        }
    }

    return B_BAD_SEM_ID;
}

static status_t benaphore_lock( benaphore_t *ben )
{
    int32 prev = atomic_add( &(ben->_atom), 1 );

    if( prev > 0 ) {
        return acquire_sem( ben->_sem );
    }

    return EOK;
}

static status_t benaphore_timedlock( benaphore_t *ben, bigtime_t micros )
{
    int32 prev = atomic_add( &(ben->_atom), 1 );

    if( prev > 0 ) {
        status_t retval = acquire_sem_etc( ben->_sem, 1, B_TIMEOUT, micros );

        switch( retval ) {
        case B_WOULD_BLOCK:             /* Fall through... */
        case B_TIMED_OUT:
            return EWOULDBLOCK;
            break;
        case B_OK:
            return EOK;
            break;
        default:
            return retval;
            break;
        }
    }

    return EOK;
}

static status_t benaphore_unlock( benaphore_t *ben )
{
    int32 prev = atomic_add( &(ben->_atom), -1 );

    if( prev > 1 ) {
        return release_sem( ben->_sem );
    }

    return EOK;
}

/* ----------------------------------------------------------------------
 * Initialization.
 */
static void PyThread__init_thread( void )
{
    /* Do nothing. */
    return;
}

/* ----------------------------------------------------------------------
 * Thread support.
 *
 * Only ANSI C, renamed functions here; you can't use K&R on BeOS,
 * and there's no legacy thread module to support.
 */

static int32 thread_count = 0;

long PyThread_start_new_thread( void (*func)(void *), void *arg )
{
    status_t success = 0;
    thread_id tid;
    char name[B_OS_NAME_LENGTH];
    int32 this_thread;

    dprintf(("PyThread_start_new_thread called\n"));

    /* We are so very thread-safe... */
    this_thread = atomic_add( &thread_count, 1 );
    PyOS_snprintf(name, sizeof(name),
                  "python thread (%d)", this_thread );

    tid = spawn_thread( (thread_func)func, name,
                        B_NORMAL_PRIORITY, arg );
    if( tid > B_NO_ERROR ) {
        success = resume_thread( tid );
    }

    return ( success == B_NO_ERROR ? tid : -1 );
}

long PyThread_get_thread_ident( void )
{
    /* Presumed to return the current thread's ID... */
    thread_id tid;
    tid = find_thread( NULL );

    return ( tid != B_NAME_NOT_FOUND ? tid : -1 );
}

void PyThread_exit_thread( void )
{
    int32 threads;

    dprintf(("PyThread_exit_thread called\n"));

    /* Thread-safe way to read a variable without a mutex: */
    threads = atomic_add( &thread_count, 0 );

    if( threads == 0 ) {
        /* No threads around, so exit main(). */
        exit(0);
    } else {
        /* Oh, we're a thread, let's try to exit gracefully... */
        exit_thread( B_NO_ERROR );
    }
}

/* ----------------------------------------------------------------------
 * Lock support.
 */

static int32 lock_count = 0;

PyThread_type_lock PyThread_allocate_lock( void )
{
    benaphore_t *lock;
    status_t retval;
    char name[B_OS_NAME_LENGTH];
    int32 this_lock;

    dprintf(("PyThread_allocate_lock called\n"));

    lock = (benaphore_t *)malloc( sizeof( benaphore_t ) );
    if( lock == NULL ) {
        /* TODO: that's bad, raise MemoryError */
        return (PyThread_type_lock)NULL;
    }

    this_lock = atomic_add( &lock_count, 1 );
    PyOS_snprintf(name, sizeof(name), "python lock (%d)", this_lock);

    retval = benaphore_create( name, lock );
    if( retval != EOK ) {
        /* TODO: that's bad, raise an exception */
        return (PyThread_type_lock)NULL;
    }

    dprintf(("PyThread_allocate_lock() -> %p\n", lock));
    return (PyThread_type_lock) lock;
}

void PyThread_free_lock( PyThread_type_lock lock )
{
    status_t retval;

    dprintf(("PyThread_free_lock(%p) called\n", lock));

    retval = benaphore_destroy( (benaphore_t *)lock );
    if( retval != EOK ) {
        /* TODO: that's bad, raise an exception */
        return;
    }
}

int PyThread_acquire_lock( PyThread_type_lock lock, int waitflag )
{
    int success;
    status_t retval;

    dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));

    if( waitflag ) {
        retval = benaphore_lock( (benaphore_t *)lock );
    } else {
        retval = benaphore_timedlock( (benaphore_t *)lock, 0 );
    }

    if( retval == EOK ) {
        success = 1;
    } else {
        success = 0;

        /* TODO: that's bad, raise an exception */
    }

    dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
    return success;
}

void PyThread_release_lock( PyThread_type_lock lock )
{
    status_t retval;

    dprintf(("PyThread_release_lock(%p) called\n", lock));

    retval = benaphore_unlock( (benaphore_t *)lock );
    if( retval != EOK ) {
        /* TODO: that's bad, raise an exception */
        return;
    }
}