cpython/Python/thread_beos.h

/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.

STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

BeOS thread support by Chris Herborth (chrish@qnx.com)
******************************************************************/

#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 _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;

int 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(("start_new_thread called\n"));

	/* We are so very thread-safe... */
	this_thread = atomic_add( &thread_count, 1 );
	sprintf( 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 ? 1 : 0 );
}

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 );
}

static void do_exit_thread( int no_cleanup )
{
	int32 threads;

	dprintf(("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(). */
		if( no_cleanup ) {
			_exit(0);
		} else {
			exit(0);
		}
	} else {
		/* Oh, we're a thread, let's try to exit gracefully... */
		exit_thread( B_NO_ERROR );
	}
}

void PyThread_exit_thread( void )
{
	do_exit_thread(0);
}

void PyThread__exit_thread( void )
{
	do_exit_thread(1);
}

#ifndef NO_EXIT_PROG
static void do_exit_prog( int status, int no_cleanup )
{
	dprintf(("exit_prog(%d) called\n", status));

	/* No need to do anything, the threads get torn down if main() exits. */

	if (no_cleanup) {
		_exit(status);
	} else {
		exit(status);
	}
}

void PyThread_exit_prog( int status )
{
	do_exit_prog(status, 0);
}

void PyThread__exit_prog( int status )
{
	do_exit_prog(status, 1);
}
#endif /* NO_EXIT_PROG */

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

static int32 lock_count = 0;

type_lock PyThread_allocate_lock( void )
{
	benaphore_t *lock;
	status_t retval;
	char name[B_OS_NAME_LENGTH];
	int32 this_lock;
	
	dprintf(("allocate_lock called\n"));

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

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

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

	dprintf(("allocate_lock() -> %lx\n", (long)lock));
	return (type_lock) lock;
}

void PyThread_free_lock( type_lock lock )
{
	status_t retval;

	dprintf(("free_lock(%lx) called\n", (long)lock));
	
	retval = benaphore_destroy( (benaphore_t *)lock );
	if( retval != EOK ) {
		/* TODO: that's bad, raise an exception */
		return;
	}
}

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

	dprintf(("acquire_lock(%lx, %d) called\n", (long)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(("acquire_lock(%lx, %d) -> %d\n", (long)lock, waitflag, success));
	return success;
}

void PyThread_release_lock( type_lock lock )
{
	status_t retval;
	
	dprintf(("release_lock(%lx) called\n", (long)lock));
	
	retval = benaphore_unlock( (benaphore_t *)lock );
	if( retval != EOK ) {
		/* TODO: that's bad, raise an exception */
		return;
	}
}

/* ----------------------------------------------------------------------
 * Semaphore support.
 *
 * Guido says not to implement this because it's not used anywhere;
 * I'll do it anyway, you never know when it might be handy, and it's
 * easy...
 */
type_sema PyThread_allocate_sema( int value )
{
	sem_id sema;
	
	dprintf(("allocate_sema called\n"));

	sema = create_sem( value, "python semaphore" );
	if( sema < B_NO_ERROR ) {
		/* TODO: that's bad, raise an exception */
		return 0;
	}

	dprintf(("allocate_sema() -> %lx\n", (long) sema));
	return (type_sema) sema;
}

void PyThread_free_sema( type_sema sema )
{
	status_t retval;
	
	dprintf(("free_sema(%lx) called\n", (long) sema));
	
	retval = delete_sem( (sem_id)sema );
	if( retval != B_NO_ERROR ) {
		/* TODO: that's bad, raise an exception */
		return;
	}
}

int PyThread_down_sema( type_sema sema, int waitflag )
{
	status_t retval;

	dprintf(("down_sema(%lx, %d) called\n", (long) sema, waitflag));

	if( waitflag ) {
		retval = acquire_sem( (sem_id)sema );
	} else {
		retval = acquire_sem_etc( (sem_id)sema, 1, B_TIMEOUT, 0 );
	}
	
	if( retval != B_NO_ERROR ) {
		/* TODO: that's bad, raise an exception */
		return 0;
	}

	dprintf(("down_sema(%lx) return\n", (long) sema));
	return -1;
}

void PyThread_up_sema( type_sema sema )
{
	status_t retval;
	
	dprintf(("up_sema(%lx)\n", (long) sema));
	
	retval = release_sem( (sem_id)sema );
	if( retval != B_NO_ERROR ) {
		/* TODO: that's bad, raise an exception */
		return;
	}
}