cpython/Python/thread_pth.h

/* GNU pth threads interface
   http://www.gnu.org/software/pth
   2000-05-03 Andy Dustman <andy@dustman.net>

   Adapted from Posix threads interface 
   12 May 1997 -- david arnold <davida@pobox.com>
 */

#include <stdlib.h>
#include <string.h>
#include <pth.h>

/* A pth mutex isn't sufficient to model the Python lock type
 * because pth mutexes can be acquired multiple times by the
 * same thread.
 *
 * The pth_lock struct implements a Python lock as a "locked?" bit
 * and a <condition, mutex> pair.  In general, if the bit can be acquired
 * instantly, it is, else the pair is used to block the thread until the
 * bit is cleared.
 */

typedef struct {
	char             locked; /* 0=unlocked, 1=locked */
	/* a <cond, mutex> pair to handle an acquire of a locked lock */
	pth_cond_t   lock_released;
	pth_mutex_t  mut;
} pth_lock;

#define CHECK_STATUS(name)  if (status == -1) { printf("%d ", status); perror(name); error = 1; }

pth_attr_t PyThread_attr;

/*
 * Initialization.
 */

static void PyThread__init_thread(void)
{
	pth_init();
	PyThread_attr = pth_attr_new();
	pth_attr_set(PyThread_attr, PTH_ATTR_STACK_SIZE, 1<<18);
	pth_attr_set(PyThread_attr, PTH_ATTR_JOINABLE, FALSE);
}

/*
 * Thread support.
 */


long PyThread_start_new_thread(void (*func)(void *), void *arg)
{
	pth_t th;
	dprintf(("PyThread_start_new_thread called\n"));
	if (!initialized)
		PyThread_init_thread();

	th = pth_spawn(PyThread_attr,
				 (void* (*)(void *))func,
				 (void *)arg
				 );

	return th;
}

long PyThread_get_thread_ident(void)
{
	volatile pth_t threadid;
	if (!initialized)
		PyThread_init_thread();
	/* Jump through some hoops for Alpha OSF/1 */
	threadid = pth_self();
	return (long) *(long *) &threadid;
}

void PyThread_exit_thread(void)
{
	dprintf(("PyThread_exit_thread called\n"));
	if (!initialized) {
		exit(0);
	}
}

/*
 * Lock support.
 */
PyThread_type_lock PyThread_allocate_lock(void)
{
	pth_lock *lock;
	int status, error = 0;

	dprintf(("PyThread_allocate_lock called\n"));
	if (!initialized)
		PyThread_init_thread();

	lock = (pth_lock *) malloc(sizeof(pth_lock));
        memset((void *)lock, '\0', sizeof(pth_lock));
	if (lock) {
		lock->locked = 0;
		status = pth_mutex_init(&lock->mut);
		CHECK_STATUS("pth_mutex_init");
		status = pth_cond_init(&lock->lock_released);
		CHECK_STATUS("pth_cond_init");
		if (error) {
			free((void *)lock);
			lock = NULL;
		}
	}
	dprintf(("PyThread_allocate_lock() -> %p\n", lock));
	return (PyThread_type_lock) lock;
}

void PyThread_free_lock(PyThread_type_lock lock)
{
	pth_lock *thelock = (pth_lock *)lock;

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

	free((void *)thelock);
}

int PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
{
	int success;
	pth_lock *thelock = (pth_lock *)lock;
	int status, error = 0;

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

	status = pth_mutex_acquire(&thelock->mut, !waitflag, NULL);
	CHECK_STATUS("pth_mutex_acquire[1]");
	success = thelock->locked == 0;
        if (success) thelock->locked = 1;
        status = pth_mutex_release( &thelock->mut );
        CHECK_STATUS("pth_mutex_release[1]");

        if ( !success && waitflag ) {
                /* continue trying until we get the lock */

                /* mut must be locked by me -- part of the condition
                 * protocol */
                status = pth_mutex_acquire( &thelock->mut, !waitflag, NULL );
                CHECK_STATUS("pth_mutex_acquire[2]");
                while ( thelock->locked ) {
                        status = pth_cond_await(&thelock->lock_released,
                                                &thelock->mut, NULL);
                        CHECK_STATUS("pth_cond_await");
                }
                thelock->locked = 1;
                status = pth_mutex_release( &thelock->mut );
                CHECK_STATUS("pth_mutex_release[2]");
                success = 1;
        }
        if (error) success = 0;
        dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
	return success;
}

void PyThread_release_lock(PyThread_type_lock lock)
{
        pth_lock *thelock = (pth_lock *)lock;
        int status, error = 0;

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

        status = pth_mutex_acquire( &thelock->mut, 0, NULL );
        CHECK_STATUS("pth_mutex_acquire[3]");

        thelock->locked = 0;

        status = pth_mutex_release( &thelock->mut );
        CHECK_STATUS("pth_mutex_release[3]");

        /* wake up someone (anyone, if any) waiting on the lock */
        status = pth_cond_notify( &thelock->lock_released, 0 );
        CHECK_STATUS("pth_cond_notify");
}