select.c

minix3.1.1源代码

/* Implement entry point to select system call.
 *
 * The entry points into this file are
 *   do_select:	       perform the SELECT system call
 *   select_callback:  notify select system of possible fd operation 
 *   select_notified:  low-level entry for device notifying select
 *   select_unsuspend_by_proc: cancel a blocking select on exiting driver
 * 
 * Changes:
 *   6 june 2005  Created (Ben Gras)
 */

#define DEBUG_SELECT 0

#include "fs.h"
#include "select.h"
#include "file.h"
#include "inode.h"

#include <sys/time.h>
#include <sys/select.h>
#include <minix/com.h>
#include <string.h>

/* max. number of simultaneously pending select() calls */
#define MAXSELECTS 25

PRIVATE struct selectentry {
	struct fproc *requestor;	/* slot is free iff this is NULL */
	int req_procnr;
	fd_set readfds, writefds, errorfds;
	fd_set ready_readfds, ready_writefds, ready_errorfds;
	fd_set *vir_readfds, *vir_writefds, *vir_errorfds;
	struct filp *filps[FD_SETSIZE];
	int type[FD_SETSIZE];
	int nfds, nreadyfds;
	clock_t expiry;
	timer_t timer;	/* if expiry > 0 */
} selecttab[MAXSELECTS];

#define SELFD_FILE	0
#define SELFD_PIPE	1
#define SELFD_TTY	2
#define SELFD_INET	3
#define SELFD_LOG	4
#define SEL_FDS		5

FORWARD _PROTOTYPE(int select_reevaluate, (struct filp *fp));

FORWARD _PROTOTYPE(int select_request_file,
	 (struct filp *f, int *ops, int block));
FORWARD _PROTOTYPE(int select_match_file, (struct filp *f));

FORWARD _PROTOTYPE(int select_request_general,
	 (struct filp *f, int *ops, int block));
FORWARD _PROTOTYPE(int select_major_match,
	(int match_major, struct filp *file));

FORWARD _PROTOTYPE(void select_cancel_all, (struct selectentry *e));
FORWARD _PROTOTYPE(void select_wakeup, (struct selectentry *e, int r));
FORWARD _PROTOTYPE(void select_return, (struct selectentry *, int));

/* The Open Group:
 * "The pselect() and select() functions shall support
 * regular files, terminal and pseudo-terminal devices,
 * STREAMS-based files, FIFOs, pipes, and sockets."
 */

PRIVATE struct fdtype {
	int (*select_request)(struct filp *, int *ops, int block);	
	int (*select_match)(struct filp *);
	int select_major;
} fdtypes[SEL_FDS] = {
		/* SELFD_FILE */
	{ select_request_file, select_match_file, 0 },
		/* SELFD_TTY (also PTY) */
	{ select_request_general, NULL, TTY_MAJOR },
		/* SELFD_INET */
	{ select_request_general, NULL, INET_MAJOR },
		/* SELFD_PIPE (pipe(2) pipes and FS FIFOs) */
	{ select_request_pipe, select_match_pipe, 0 },
		/* SELFD_LOG (/dev/klog) */
	{ select_request_general, NULL, LOG_MAJOR },
};

/* Open Group:
 * "File descriptors associated with regular files shall always select true
 * for ready to read, ready to write, and error conditions."
 */

/*===========================================================================*
 *				select_request_file			     *
 *===========================================================================*/
PRIVATE int select_request_file(struct filp *f, int *ops, int block)
{
	/* output *ops is input *ops */
	return SEL_OK;
}

/*===========================================================================*
 *				select_match_file			     *
 *===========================================================================*/
PRIVATE int select_match_file(struct filp *file)
{
	if (file && file->filp_ino && (file->filp_ino->i_mode & I_REGULAR))
		return 1;
	return 0;
}

/*===========================================================================*
 *				select_request_general			     *
 *===========================================================================*/
PRIVATE int select_request_general(struct filp *f, int *ops, int block)
{
	int rops = *ops;
	if (block) rops |= SEL_NOTIFY;
	*ops = dev_io(DEV_SELECT, f->filp_ino->i_zone[0], rops, NULL, 0, 0, 0);
	if (*ops < 0)
		return SEL_ERR;
	return SEL_OK;
}

/*===========================================================================*
 *				select_major_match			     *
 *===========================================================================*/
PRIVATE int select_major_match(int match_major, struct filp *file)
{
	int major;
	if (!(file && file->filp_ino &&
		(file->filp_ino->i_mode & I_TYPE) == I_CHAR_SPECIAL))
		return 0;
	major = (file->filp_ino->i_zone[0] >> MAJOR) & BYTE;
	if (major == match_major)
		return 1;
	return 0;
}

/*===========================================================================*
 *				tab2ops					     *
 *===========================================================================*/
PRIVATE int tab2ops(int fd, struct selectentry *e)
{
	return (FD_ISSET(fd, &e->readfds) ? SEL_RD : 0) |
		(FD_ISSET(fd, &e->writefds) ? SEL_WR : 0) |
		(FD_ISSET(fd, &e->errorfds) ? SEL_ERR : 0);
}

/*===========================================================================*
 *				ops2tab					     *
 *===========================================================================*/
PRIVATE void ops2tab(int ops, int fd, struct selectentry *e)
{
	if ((ops & SEL_RD) && e->vir_readfds && FD_ISSET(fd, &e->readfds)
	        && !FD_ISSET(fd, &e->ready_readfds)) {
		FD_SET(fd, &e->ready_readfds);
		e->nreadyfds++;
	}
	if ((ops & SEL_WR) && e->vir_writefds && FD_ISSET(fd, &e->writefds) 
		&& !FD_ISSET(fd, &e->ready_writefds)) {
		FD_SET(fd, &e->ready_writefds);
		e->nreadyfds++;
	}
	if ((ops & SEL_ERR) && e->vir_errorfds && FD_ISSET(fd, &e->errorfds)
		&& !FD_ISSET(fd, &e->ready_errorfds)) {
		FD_SET(fd, &e->ready_errorfds);
		e->nreadyfds++;
	}

	return;
}

/*===========================================================================*
 *				copy_fdsets				     *
 *===========================================================================*/
PRIVATE void copy_fdsets(struct selectentry *e)
{
	if (e->vir_readfds)
		sys_vircopy(SELF, D, (vir_bytes) &e->ready_readfds,
		e->req_procnr, D, (vir_bytes) e->vir_readfds, sizeof(fd_set));
	if (e->vir_writefds)
		sys_vircopy(SELF, D, (vir_bytes) &e->ready_writefds,
		e->req_procnr, D, (vir_bytes) e->vir_writefds, sizeof(fd_set));
	if (e->vir_errorfds)
		sys_vircopy(SELF, D, (vir_bytes) &e->ready_errorfds,
		e->req_procnr, D, (vir_bytes) e->vir_errorfds, sizeof(fd_set));

	return;
}

/*===========================================================================*
 *				do_select				      *
 *===========================================================================*/
PUBLIC int do_select(void)
{
	int r, nfds, is_timeout = 1, nonzero_timeout = 0,
		fd, s, block = 0;
	struct timeval timeout;
	nfds = m_in.SEL_NFDS;

	if (nfds < 0 || nfds > FD_SETSIZE)
		return EINVAL;

	for(s = 0; s < MAXSELECTS; s++)
		if (!selecttab[s].requestor)
			break;

	if (s >= MAXSELECTS)
		return ENOSPC;

	selecttab[s].req_procnr = who;
	selecttab[s].nfds = 0;
	selecttab[s].nreadyfds = 0;
	memset(selecttab[s].filps, 0, sizeof(selecttab[s].filps));

	/* defaults */
	FD_ZERO(&selecttab[s].readfds);
	FD_ZERO(&selecttab[s].writefds);
	FD_ZERO(&selecttab[s].errorfds);
	FD_ZERO(&selecttab[s].ready_readfds);
	FD_ZERO(&selecttab[s].ready_writefds);
	FD_ZERO(&selecttab[s].ready_errorfds);

	selecttab[s].vir_readfds = (fd_set *) m_in.SEL_READFDS;
	selecttab[s].vir_writefds = (fd_set *) m_in.SEL_WRITEFDS;
	selecttab[s].vir_errorfds = (fd_set *) m_in.SEL_ERRORFDS;

	/* copy args */
	if (selecttab[s].vir_readfds
	 && (r=sys_vircopy(who, D, (vir_bytes) m_in.SEL_READFDS,
		SELF, D, (vir_bytes) &selecttab[s].readfds, sizeof(fd_set))) != OK)
		return r;

	if (selecttab[s].vir_writefds
	 && (r=sys_vircopy(who, D, (vir_bytes) m_in.SEL_WRITEFDS,
		SELF, D, (vir_bytes) &selecttab[s].writefds, sizeof(fd_set))) != OK)
		return r;

	if (selecttab[s].vir_errorfds
	 && (r=sys_vircopy(who, D, (vir_bytes) m_in.SEL_ERRORFDS,
		SELF, D, (vir_bytes) &selecttab[s].errorfds, sizeof(fd_set))) != OK)
		return r;

	if (!m_in.SEL_TIMEOUT)
		is_timeout = nonzero_timeout = 0;
	else
		if ((r=sys_vircopy(who, D, (vir_bytes) m_in.SEL_TIMEOUT,
			SELF, D, (vir_bytes) &timeout, sizeof(timeout))) != OK)
			return r;

	/* No nonsense in the timeval please. */
	if (is_timeout && (timeout.tv_sec < 0 || timeout.tv_usec < 0))
		return EINVAL;

	/* if is_timeout if 0, we block forever. otherwise, if nonzero_timeout
	 * is 0, we do a poll (don't block). otherwise, we block up to the
	 * specified time interval.
	 */
	if (is_timeout && (timeout.tv_sec > 0 || timeout.tv_usec > 0))
		nonzero_timeout = 1;

	if (nonzero_timeout || !is_timeout)
		block = 1;
	else
		block = 0; /* timeout set as (0,0) - this effects a poll */

	/* no timeout set (yet) */
	selecttab[s].expiry = 0;

	for(fd = 0; fd < nfds; fd++) {
		int orig_ops, ops, t, type = -1, r;
		struct filp *filp;
	
		if (!(orig_ops = ops = tab2ops(fd, &selecttab[s])))
			continue;
		if (!(filp = selecttab[s].filps[fd] = get_filp(fd))) {
			select_cancel_all(&selecttab[s]);
			return EBADF;
		}

		for(t = 0; t < SEL_FDS; t++) {
			if (fdtypes[t].select_match) {
			   if (fdtypes[t].select_match(filp)) {
#if DEBUG_SELECT
				printf("select: fd %d is type %d ", fd, t);
#endif
				if (type != -1)
					printf("select: double match\n");
				type = t;
			  }
	 		} else if (select_major_match(fdtypes[t].select_major, filp)) {
				type = t;
			}
		}

		/* Open Group:
		 * "The pselect() and select() functions shall support
		 * regular files, terminal and pseudo-terminal devices,
		 * STREAMS-based files, FIFOs, pipes, and sockets. The
		 * behavior of pselect() and select() on file descriptors
		 * that refer to other types of file is unspecified."
		 *
		 * If all types are implemented, then this is another
		 * type of file and we get to do whatever we want.
		 */
		if (type == -1)
		{
#if DEBUG_SELECT
			printf("do_select: bad type\n");
#endif
			return EBADF;
		}

		selecttab[s].type[fd] = type;

		if ((selecttab[s].filps[fd]->filp_select_ops & ops) != ops) {
			int wantops;
			/* Request the select on this fd.  */
#if DEBUG_SELECT
			printf("%p requesting ops %d -> ",
				selecttab[s].filps[fd],
				selecttab[s].filps[fd]->filp_select_ops);
#endif
			wantops = (selecttab[s].filps[fd]->filp_select_ops |= ops);
#if DEBUG_SELECT
			printf("%d\n", selecttab[s].filps[fd]->filp_select_ops);
#endif
			if ((r = fdtypes[type].select_request(filp,
				&wantops, block)) != SEL_OK) {
				/* error or bogus return code.. backpaddle */
				select_cancel_all(&selecttab[s]);
				printf("select: select_request returned error\n");
				return EINVAL;
			}
			if (wantops) {
				if (wantops & ops) {
					/* operations that were just requested
					 * are ready to go right away
					 */
					ops2tab(wantops, fd, &selecttab[s]);
				}
				/* if there are any other select()s blocking
				 * on these operations of this fp, they can
				 * be awoken too
				 */
				select_callback(filp, ops);
			}
#if DEBUG_SELECT
			printf("select request ok; ops returned %d\n", wantops);
#endif
		} else {
#if DEBUG_SELECT
			printf("select already happening on that filp\n");