select.c

minix3的源码

#endif
		}

		selecttab[s].nfds = fd+1;
		selecttab[s].filps[fd]->filp_selectors++;

#if DEBUG_SELECT
		printf("[fd %d ops: %d] ", fd, ops);
#endif
	}

	if (selecttab[s].nreadyfds > 0 || !block) {
		/* fd's were found that were ready to go right away, and/or
		 * we were instructed not to block at all. Must return
		 * immediately.
		 */
		copy_fdsets(&selecttab[s]);
		select_cancel_all(&selecttab[s]);
		selecttab[s].requestor = NULL;

		/* Open Group:
		 * "Upon successful completion, the pselect() and select()
		 * functions shall return the total number of bits
		 * set in the bit masks."
		 */
#if DEBUG_SELECT
		printf("returning\n");
#endif

		return selecttab[s].nreadyfds;
	}
#if DEBUG_SELECT
		printf("not returning (%d, %d)\n", selecttab[s].nreadyfds, block);
#endif
 
	/* Convert timeval to ticks and set the timer. If it fails, undo
	 * all, return error.
	 */
	if (is_timeout) {
		int ticks;
		/* Open Group:
		 * "If the requested timeout interval requires a finer
		 * granularity than the implementation supports, the
		 * actual timeout interval shall be rounded up to the next
		 * supported value."
		 */
#define USECPERSEC 1000000
		while(timeout.tv_usec >= USECPERSEC) {
			/* this is to avoid overflow with *HZ below */
			timeout.tv_usec -= USECPERSEC;
			timeout.tv_sec++;
		}
		ticks = timeout.tv_sec * HZ +
			(timeout.tv_usec * HZ + USECPERSEC-1) / USECPERSEC;
		selecttab[s].expiry = ticks;
		fs_set_timer(&selecttab[s].timer, ticks, select_timeout_check, s);
#if DEBUG_SELECT
		printf("%d: blocking %d ticks\n", s, ticks);
#endif
	}

	/* if we're blocking, the table entry is now valid. */
	selecttab[s].requestor = fp;

	/* process now blocked */
	suspend(XSELECT);
	return SUSPEND;
}

/*===========================================================================*
 *				select_cancel_all			     *
 *===========================================================================*/
PRIVATE void select_cancel_all(struct selectentry *e)
{
	int fd;

	for(fd = 0; fd < e->nfds; fd++) {
		struct filp *fp;
		fp = e->filps[fd];
		if (!fp) {
#if DEBUG_SELECT
			printf("[ fd %d/%d NULL ] ", fd, e->nfds);
#endif
			continue;
		}
		if (fp->filp_selectors < 1) {
#if DEBUG_SELECT
			printf("select: %d selectors?!\n", fp->filp_selectors);
#endif
			continue;
		}
		fp->filp_selectors--;
		e->filps[fd] = NULL;
		select_reevaluate(fp);
	}

	if (e->expiry > 0) {
#if DEBUG_SELECT
		printf("cancelling timer %d\n", e - selecttab);
#endif
		fs_cancel_timer(&e->timer); 
		e->expiry = 0;
	}

	return;
}

/*===========================================================================*
 *				select_wakeup				     *
 *===========================================================================*/
PRIVATE void select_wakeup(struct selectentry *e, int r)
{
	revive(e->req_procnr, r);
}

/*===========================================================================*
 *				select_reevaluate			     *
 *===========================================================================*/
PRIVATE int select_reevaluate(struct filp *fp)
{
	int s, remain_ops = 0, fd, type = -1;

	if (!fp) {
		printf("fs: select: reevalute NULL fp\n");
		return 0;
	}

	for(s = 0; s < MAXSELECTS; s++) {
		if (!selecttab[s].requestor)
			continue;
		for(fd = 0; fd < selecttab[s].nfds; fd++)
			if (fp == selecttab[s].filps[fd]) {
				remain_ops |= tab2ops(fd, &selecttab[s]);
				type = selecttab[s].type[fd];
			}
	}

	/* If there are any select()s open that want any operations on
	 * this fd that haven't been satisfied by this callback, then we're
	 * still in the market for it.
	 */
	fp->filp_select_ops = remain_ops;
#if DEBUG_SELECT
	printf("remaining operations on fp are %d\n", fp->filp_select_ops);
#endif

	return remain_ops;
}

/*===========================================================================*
 *				select_return				     *
 *===========================================================================*/
PRIVATE void select_return(struct selectentry *s, int r)
{
	select_cancel_all(s);
	copy_fdsets(s);
	select_wakeup(s, r ? r : s->nreadyfds);
	s->requestor = NULL;
}

/*===========================================================================*
 *				select_callback			             *
 *===========================================================================*/
PUBLIC int select_callback(struct filp *fp, int ops)
{
	int s, fd, want_ops, type;

	/* We are being notified that file pointer fp is available for
	 * operations 'ops'. We must re-register the select for
	 * operations that we are still interested in, if any.
	 */

	want_ops = 0;
	type = -1;
	for(s = 0; s < MAXSELECTS; s++) {
		int wakehim = 0;
		if (!selecttab[s].requestor)
			continue;
		for(fd = 0; fd < selecttab[s].nfds; fd++) {
			if (!selecttab[s].filps[fd])
				continue;
			if (selecttab[s].filps[fd] == fp) {
				int this_want_ops;
				this_want_ops = tab2ops(fd, &selecttab[s]);
				want_ops |= this_want_ops;
				if (this_want_ops & ops) {
					/* this select() has been satisfied. */
					ops2tab(ops, fd, &selecttab[s]);
					wakehim = 1;
				}
				type = selecttab[s].type[fd];
			}
		}
		if (wakehim)
			select_return(&selecttab[s], 0);
	}

	return 0;
}

/*===========================================================================*
 *				select_notified			             *
 *===========================================================================*/
PUBLIC int select_notified(int major, int minor, int selected_ops)
{
	int s, f, t;

#if DEBUG_SELECT
	printf("select callback: %d, %d: %d\n", major, minor, selected_ops);
#endif

	for(t = 0; t < SEL_FDS; t++)
		if (!fdtypes[t].select_match && fdtypes[t].select_major == major)
		    	break;

	if (t >= SEL_FDS) {
#if DEBUG_SELECT
		printf("select callback: no fdtype found for device %d\n", major);
#endif
		return OK;
	}

	/* We have a select callback from major device no.
	 * d, which corresponds to our select type t.
	 */

	for(s = 0; s < MAXSELECTS; s++) {
		int s_minor, ops;
		if (!selecttab[s].requestor)
			continue;
		for(f = 0; f < selecttab[s].nfds; f++) {
			if (!selecttab[s].filps[f] ||
			   !select_major_match(major, selecttab[s].filps[f]))
			   	continue;
			ops = tab2ops(f, &selecttab[s]);
			s_minor =
			(selecttab[s].filps[f]->filp_ino->i_zone[0] >> MINOR)
				& BYTE;
			if ((s_minor == minor) &&
				(selected_ops & ops)) {
				select_callback(selecttab[s].filps[f], (selected_ops & ops));
			}
		}
	}

	return OK;
}

/*===========================================================================*
 *				init_select  				     *
 *===========================================================================*/
PUBLIC void init_select(void)
{
	int s;

	for(s = 0; s < MAXSELECTS; s++)
		fs_init_timer(&selecttab[s].timer);
}

/*===========================================================================*
 *				select_forget			             *
 *===========================================================================*/
PUBLIC void select_forget(int proc)
{
	/* something has happened (e.g. signal delivered that interrupts
	 * select()). totally forget about the select().
	 */
	int s;

	for(s = 0; s < MAXSELECTS; s++) {
		if (selecttab[s].requestor &&
			selecttab[s].req_procnr == proc) {
			break;
		}

	}

	if (s >= MAXSELECTS) {
#if DEBUG_SELECT
		printf("select: cancelled select() not found");
#endif
		return;
	}

	select_cancel_all(&selecttab[s]);
	selecttab[s].requestor = NULL;

	return;
}

/*===========================================================================*
 *				select_timeout_check	  	     	     *
 *===========================================================================*/
PUBLIC void select_timeout_check(timer_t *timer)
{
	int s;

	s = tmr_arg(timer)->ta_int;

	if (s < 0 || s >= MAXSELECTS) {
#if DEBUG_SELECT
		printf("select: bogus slot arg to watchdog %d\n", s);
#endif
		return;
	}

	if (!selecttab[s].requestor) {
#if DEBUG_SELECT
		printf("select: no requestor in watchdog\n");
#endif
		return;
	}

	if (selecttab[s].expiry <= 0) {
#if DEBUG_SELECT
		printf("select: strange expiry value in watchdog\n", s);
#endif
		return;
	}

	selecttab[s].expiry = 0;
	select_return(&selecttab[s], 0);

	return;
}

/*===========================================================================*
 *				select_unsuspend_by_proc  	     	     *
 *===========================================================================*/
PUBLIC void select_unsuspend_by_proc(int proc)
{
	struct filp *fp;
	int fd, s;

	for(s = 0; s < MAXSELECTS; s++) {
	  if (!selecttab[s].requestor)
		  continue;
	  for(fd = 0; fd < selecttab[s].nfds; fd++) {
	    int maj;
	    if (!selecttab[s].filps[fd] || !selecttab[s].filps[fd]->filp_ino)
		continue;
	    maj = (selecttab[s].filps[fd]->filp_ino->i_zone[0] >> MAJOR)&BYTE;
	    if(dmap_driver_match(proc, maj)) {
			select_return(&selecttab[s], EAGAIN);
	    }
	  }
	}

	return;
}