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minix/servers/fs/select.c
Ben Gras b5e3e6d18c Two 'dynamic driver' features in FS: 
.  When drivers disappear that have pending select()s, wake up
   those user processes with EAGAIN so that they can retry their
   select() and won't hang forever on it.
.  When drivers re-appear and are mapped into the dmap, run through
   the list of mounted filesystems and re-dev_open() every one (for
   partition tables and such). This can't happen before the driver
   has exec()ced itself, so processes that have fork()ed but not
   exec()ced yet are marked as DMAP_BABY in the dmap table if they
   are dmapped before they are execced. If that happens, the above
   procedure happens after the exec(). If the exec() happens before
   the dmapping, it (the dev_open()ing) happens right away.
2005-10-20 19:39:32 +00:00

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/* 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");
#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;
}
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