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minix/servers/avfs/select.c
Thomas Veerman abd6043a2f AVFS: fix various system call interruption issues 
- When cancelling ioctls, VFS did not remember which file descriptor
   to cancel and sent bogus to the driver.
 - Select state was not cleaned up when select()ing process was
   interrupted.
 - Process trying to do a system call at the exact same time as a user
   trying to interrupt the process, could cause the system call worker
   thread to overwrite state belonging to the worker thread trying to
   exit the process. This led to hanging threads and eventual system hang
   when this happens often enough.
2012-02-09 14:24:28 +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_unsuspend_by_endpt: cancel a blocking select on exiting driver
*/
#include "fs.h"
#include <sys/time.h>
#include <sys/select.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <string.h>
#include <assert.h>
#include "select.h"
#include "file.h"
#include "fproc.h"
#include "dmap.h"
#include "vnode.h"
/* max. number of simultaneously pending select() calls */
#define MAXSELECTS 25
#define FROM_PROC 0
#define TO_PROC 1
PRIVATE struct selectentry {
struct fproc *requestor; /* slot is free iff this is NULL */
endpoint_t req_endpt;
fd_set readfds, writefds, errorfds;
fd_set ready_readfds, ready_writefds, ready_errorfds;
fd_set *vir_readfds, *vir_writefds, *vir_errorfds;
struct filp *filps[OPEN_MAX];
int type[OPEN_MAX];
int nfds, nreadyfds;
int error;
char block;
clock_t expiry;
timer_t timer; /* if expiry > 0 */
} selecttab[MAXSELECTS];
FORWARD _PROTOTYPE(int copy_fdsets, (struct selectentry *se, int nfds,
int direction) );
FORWARD _PROTOTYPE(int do_select_request, (struct selectentry *se, int fd,
int *ops) );
FORWARD _PROTOTYPE(void filp_status, (struct filp *fp, int status) );
FORWARD _PROTOTYPE(int is_deferred, (struct selectentry *se) );
FORWARD _PROTOTYPE(void restart_proc, (struct selectentry *se) );
FORWARD _PROTOTYPE(void ops2tab, (int ops, int fd, struct selectentry *e));
FORWARD _PROTOTYPE(int is_regular_file, (struct filp *f) );
FORWARD _PROTOTYPE(int is_pipe, (struct filp *f) );
FORWARD _PROTOTYPE(int is_supported_major, (struct filp *f) );
FORWARD _PROTOTYPE(void select_lock_filp, (struct filp *f, int ops) );
FORWARD _PROTOTYPE(int select_request_async, (struct filp *f, int *ops,
int block) );
FORWARD _PROTOTYPE(int select_request_file, (struct filp *f, int *ops,
int block) );
FORWARD _PROTOTYPE(int select_request_major, (struct filp *f, int *ops,
int block) );
FORWARD _PROTOTYPE(int select_request_pipe, (struct filp *f, int *ops,
int block) );
FORWARD _PROTOTYPE(int select_request_sync, (struct filp *f, int *ops,
int block) );
FORWARD _PROTOTYPE(void select_cancel_all, (struct selectentry *e) );
FORWARD _PROTOTYPE(void select_cancel_filp, (struct filp *f) );
FORWARD _PROTOTYPE(void select_return, (struct selectentry *) );
FORWARD _PROTOTYPE(void select_restart_filps, (void) );
FORWARD _PROTOTYPE(int tab2ops, (int fd, struct selectentry *e) );
FORWARD _PROTOTYPE(void wipe_select, (struct selectentry *s) );
PRIVATE struct fdtype {
int (*select_request)(struct filp *, int *ops, int block);
int (*type_match)(struct filp *f);
} fdtypes[] = {
{ select_request_major, is_supported_major },
{ select_request_file, is_regular_file },
{ select_request_pipe, is_pipe },
};
#define SEL_FDS (sizeof(fdtypes) / sizeof(fdtypes[0]))
PRIVATE int select_majors[] = { /* List of majors that support selecting on */
TTY_MAJOR,
INET_MAJOR,
UDS_MAJOR,
LOG_MAJOR,
};
#define SEL_MAJORS (sizeof(select_majors) / sizeof(select_majors[0]))
/*===========================================================================*
* do_select *
*===========================================================================*/
PUBLIC int do_select(void)
{
/* Implement the select(nfds, readfds, writefds, errorfds, timeout) system
* call. First we copy the arguments and verify their sanity. Then we check
* whether there are file descriptors that satisfy the select call right of the
* bat. If so, or if there are no ready file descriptors but the process
* requested to return immediately, we return the result. Otherwise we set a
* timeout and wait for either the file descriptors to become ready or the
* timer to go off. If no timeout value was provided, we wait indefinitely. */
int r, nfds, do_timeout = 0, fd, s;
struct timeval timeout;
struct selectentry *se;
nfds = m_in.SEL_NFDS;
/* Sane amount of file descriptors? */
if (nfds < 0 || nfds > OPEN_MAX) return(EINVAL);
/* Find a slot to store this select request */
for (s = 0; s < MAXSELECTS; s++)
if (selecttab[s].requestor == NULL) /* Unused slot */
break;
if (s >= MAXSELECTS) return(ENOSPC);
se = &selecttab[s];
wipe_select(se); /* Clear results of previous usage */
se->req_endpt = who_e;
se->vir_readfds = (fd_set *) m_in.SEL_READFDS;
se->vir_writefds = (fd_set *) m_in.SEL_WRITEFDS;
se->vir_errorfds = (fd_set *) m_in.SEL_ERRORFDS;
/* Copy fdsets from the process */
if ((r = copy_fdsets(se, nfds, FROM_PROC)) != OK) return(r);
/* Did the process set a timeout value? If so, retrieve it. */
if (m_in.SEL_TIMEOUT != NULL) {
do_timeout = 1;
r = sys_vircopy(who_e, D, (vir_bytes) m_in.SEL_TIMEOUT, SELF, D,
(vir_bytes) &timeout, sizeof(timeout));
if (r != OK) return(r);
}
/* No nonsense in the timeval */
if (do_timeout && (timeout.tv_sec < 0 || timeout.tv_usec < 0))
return(EINVAL);
/* If there is no timeout, we block forever. Otherwise, we block up to the
* specified time interval.
*/
if (!do_timeout) /* No timeout value set */
se->block = 1;
else if (do_timeout && (timeout.tv_sec > 0 || timeout.tv_usec > 0))
se->block = 1;
else /* timeout set as (0,0) - this effects a poll */
se->block = 0;
se->expiry = 0; /* no timer set (yet) */
/* Verify that file descriptors are okay to select on */
for (fd = 0; fd < nfds; fd++) {
struct filp *f;
int type, ops;
/* Because the select() interface implicitly includes file descriptors
* you might not want to select on, we have to figure out whether we're
* interested in them. Typically, these file descriptors include fd's
* inherited from the parent proc and file descriptors that have been
* close()d, but had a lower fd than one in the current set.
*/
if (!(ops = tab2ops(fd, se)))
continue; /* No operations set; nothing to do for this fd */
/* Get filp belonging to this fd */
f = se->filps[fd] = get_filp(fd, VNODE_READ);
if (f == NULL) {
if (err_code == EBADF)
r = err_code;
else /* File descriptor is 'ready' to return EIO */
r = EINTR;
return(r);
}
/* Check file types. According to POSIX 2008:
* "The pselect() and select() functions shall support regular files,
* terminal and pseudo-terminal devices, FIFOs, pipes, and sockets. The
* behavior of pselect() and select() on file descriptors that refer to
* other types of file is unspecified."
*
* In our case, terminal and pseudo-terminal devices are handled by the
* TTY major and sockets by either INET major (socket type AF_INET) or
* PFS major (socket type AF_UNIX). PFS acts as an FS when it handles
* pipes and as a driver when it handles sockets. Additionally, we
* support select on the LOG major to handle kernel logging, which is
* beyond the POSIX spec. */
se->type[fd] = -1;
for (type = 0; type < SEL_FDS; type++) {
if (fdtypes[type].type_match(f)) {
se->type[fd] = type;
se->nfds = fd+1;
se->filps[fd]->filp_selectors++;
break;
}
}
unlock_filp(f);
if (se->type[fd] == -1) /* Type not found */
return(EBADF);
}
/* Check all file descriptors in the set whether one is 'ready' now */
for (fd = 0; fd < nfds; fd++) {
int ops, r;
struct filp *f;
/* Again, check for involuntarily selected fd's */
if (!(ops = tab2ops(fd, se)))
continue; /* No operations set; nothing to do for this fd */
/* Test filp for select operations if not already done so. e.g.,
* processes sharing a filp and both doing a select on that filp. */
f = se->filps[fd];
select_lock_filp(f, f->filp_select_ops | ops);
if ((f->filp_select_ops & ops) != ops) {
int wantops;
wantops = (f->filp_select_ops |= ops);
r = do_select_request(se, fd, &wantops);
unlock_filp(f);
if (r != SEL_OK) {
if (r == SEL_DEFERRED) continue;
else break; /* Error or bogus return code; abort */
}
/* The select request above might have turned on/off some
* operations because they were 'ready' or not meaningful.
* Either way, we might have a result and we need to store them
* in the select table entry. */
if (wantops & ops) ops2tab(wantops, fd, se);
} else {
unlock_filp(f);
}
}
if ((se->nreadyfds > 0 || !se->block) && !is_deferred(se)) {
/* fd's were found that were ready to go right away, and/or
* we were instructed not to block at all. Must return
* immediately.
*/
r = copy_fdsets(se, se->nfds, TO_PROC);
select_cancel_all(se);
if (r != OK)
return(r);
else if (se->error != OK)
return(se->error);
return(se->nreadyfds);
}
/* Convert timeval to ticks and set the timer. If it fails, undo
* all, return error.
*/
if (do_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 *system_hz below */
timeout.tv_usec -= USECPERSEC;
timeout.tv_sec++;
}
ticks = timeout.tv_sec * system_hz +
(timeout.tv_usec * system_hz + USECPERSEC-1) / USECPERSEC;
se->expiry = ticks;
set_timer(&se->timer, ticks, select_timeout_check, s);
}
/* If we're blocking, the table entry is now valid */
se->requestor = fp;
/* process now blocked */
suspend(FP_BLOCKED_ON_SELECT);
return(SUSPEND);
}
/*===========================================================================*
* is_deferred *
*===========================================================================*/
PRIVATE int is_deferred(struct selectentry *se)
{
/* Find out whether this select has pending initial replies */
int fd;
struct filp *f;
for (fd = 0; fd < se->nfds; fd++) {
if ((f = se->filps[fd]) == NULL) continue;
if (f->filp_select_flags & (FSF_UPDATE|FSF_BUSY)) return(TRUE);
}
return(FALSE);
}
/*===========================================================================*
* is_regular_file *
*===========================================================================*/
PRIVATE int is_regular_file(struct filp *f)
{
return(f && f->filp_vno && (f->filp_vno->v_mode & I_TYPE) == I_REGULAR);
}
/*===========================================================================*
* is_pipe *
*===========================================================================*/
PRIVATE int is_pipe(struct filp *f)
{
/* Recognize either anonymous pipe or named pipe (FIFO) */
return(f && f->filp_vno && (f->filp_vno->v_mode & I_TYPE) == I_NAMED_PIPE);
}
/*===========================================================================*
* is_supported_major *
*===========================================================================*/
PRIVATE int is_supported_major(struct filp *f)
{
/* See if this filp is a handle on a device on which we support select() */
int m;
if (!(f && f->filp_vno)) return(FALSE);
if ((f->filp_vno->v_mode & I_TYPE) != I_CHAR_SPECIAL) return(FALSE);
for (m = 0; m < SEL_MAJORS; m++)
if (major(f->filp_vno->v_sdev) == select_majors[m])
return(TRUE);
return(FALSE);
}
/*===========================================================================*
* select_request_async *
*===========================================================================*/
PRIVATE int select_request_async(struct filp *f, int *ops, int block)
{
int r, rops, major;
struct dmap *dp;
rops = *ops;
if (!block && (f->filp_select_flags & FSF_BLOCKED)) {
/* This filp is blocked waiting for a reply, but we don't want to
* block ourselves. Unless we're awaiting the initial reply, these
* operations won't be ready */
if (!(f->filp_select_flags & FSF_BUSY)) {
if ((rops & SEL_RD) && (f->filp_select_flags & FSF_RD_BLOCK))
rops &= ~SEL_RD;
if ((rops & SEL_WR) && (f->filp_select_flags & FSF_WR_BLOCK))
rops &= ~SEL_WR;
if ((rops & SEL_ERR) && (f->filp_select_flags & FSF_ERR_BLOCK))
rops &= ~SEL_ERR;
if (!(rops & (SEL_RD|SEL_WR|SEL_ERR))) {
/* Nothing left to do */
*ops = 0;
return(SEL_OK);
}
}
}
f->filp_select_flags |= FSF_UPDATE;
if (block) {
rops |= SEL_NOTIFY;
if (rops & SEL_RD) f->filp_select_flags |= FSF_RD_BLOCK;
if (rops & SEL_WR) f->filp_select_flags |= FSF_WR_BLOCK;
if (rops & SEL_ERR) f->filp_select_flags |= FSF_ERR_BLOCK;
}
if (f->filp_select_flags & FSF_BUSY)
return(SEL_DEFERRED);
major = major(f->filp_vno->v_sdev);
if (major < 0 || major >= NR_DEVICES) return(SEL_ERROR);
dp = &dmap[major];
if (dp->dmap_sel_filp)
return(SEL_DEFERRED);
f->filp_select_flags &= ~FSF_UPDATE;
r = dev_io(VFS_DEV_SELECT, f->filp_vno->v_sdev, rops, NULL,
cvu64(0), 0, 0, FALSE);
if (r < 0 && r != SUSPEND)
return(SEL_ERROR);
if (r != SUSPEND)
panic("select_request_asynch: expected SUSPEND got: %d", r);
dp->dmap_sel_filp = f;
f->filp_select_flags |= FSF_BUSY;
return(SEL_DEFERRED);
}
/*===========================================================================*
* select_request_file *
*===========================================================================*/
PRIVATE int select_request_file(struct filp *UNUSED(f), int *UNUSED(ops),
int UNUSED(block))
{
/* Files are always ready, so output *ops is input *ops */
return(SEL_OK);
}
/*===========================================================================*
* select_request_major *
*===========================================================================*/
PRIVATE int select_request_major(struct filp *f, int *ops, int block)
{
int major, r;
major = major(f->filp_vno->v_sdev);
if (major < 0 || major >= NR_DEVICES) return(SEL_ERROR);
if (dmap[major].dmap_style == STYLE_DEVA ||
dmap[major].dmap_style == STYLE_CLONE_A)
r = select_request_async(f, ops, block);
else
r = select_request_sync(f, ops, block);
return(r);
}
/*===========================================================================*
* select_request_sync *
*===========================================================================*/
PRIVATE int select_request_sync(struct filp *f, int *ops, int block)
{
int rops;
rops = *ops;
if (block) rops |= SEL_NOTIFY;
*ops = dev_io(VFS_DEV_SELECT, f->filp_vno->v_sdev, rops, NULL,
cvu64(0), 0, 0, FALSE);
if (*ops < 0)
return(SEL_ERROR);
return(SEL_OK);
}
/*===========================================================================*
* select_request_pipe *
*===========================================================================*/
PRIVATE int select_request_pipe(struct filp *f, int *ops, int block)
{
int orig_ops, r = 0, err;
orig_ops = *ops;
if ((*ops & (SEL_RD|SEL_ERR))) {
err = pipe_check(f->filp_vno, READING, 0, 1, f->filp_pos, 1);
if (err != SUSPEND)
r |= SEL_RD;
if (err < 0 && err != SUSPEND)
r |= SEL_ERR;
if (err == SUSPEND && !(f->filp_mode & R_BIT)) {
/* A "meaningless" read select, therefore ready
* for reading and no error set. */
r |= SEL_RD;
r &= ~SEL_ERR;
}
}
if ((*ops & (SEL_WR|SEL_ERR))) {
err = pipe_check(f->filp_vno, WRITING, 0, 1, f->filp_pos, 1);
if (err != SUSPEND)
r |= SEL_WR;
if (err < 0 && err != SUSPEND)
r |= SEL_ERR;
if (err == SUSPEND && !(f->filp_mode & W_BIT)) {
/* A "meaningless" write select, therefore ready
for writing and no error set. */
r |= SEL_WR;
r &= ~SEL_ERR;
}
}
/* Some options we collected might not be requested. */
*ops = r & orig_ops;
if (!*ops && block)
f->filp_pipe_select_ops |= orig_ops;
return(SEL_OK);
}
/*===========================================================================*
* tab2ops *
*===========================================================================*/
PRIVATE int tab2ops(int fd, struct selectentry *e)
{
int ops = 0;
if (FD_ISSET(fd, &e->readfds)) ops |= SEL_RD;
if (FD_ISSET(fd, &e->writefds)) ops |= SEL_WR;
if (FD_ISSET(fd, &e->errorfds)) ops |= SEL_ERR;
return(ops);
}
/*===========================================================================*
* 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++;
}
}
/*===========================================================================*
* copy_fdsets *
*===========================================================================*/
PRIVATE int copy_fdsets(struct selectentry *se, int nfds, int direction)
{
int r;
size_t fd_setsize;
endpoint_t src_e, dst_e;
fd_set *src_fds, *dst_fds;
if (nfds < 0 || nfds > OPEN_MAX)
panic("select copy_fdsets: nfds wrong: %d", nfds);
/* Only copy back as many bits as the user expects. */
#ifdef __NBSD_LIBC
fd_setsize = (size_t) (howmany(nfds, __NFDBITS) * sizeof(__fd_mask));
#else
fd_setsize = (size_t) (_FDSETWORDS(nfds) * _FDSETBITSPERWORD/8);
#endif
/* Set source and destination endpoints */
src_e = (direction == FROM_PROC) ? se->req_endpt : SELF;
dst_e = (direction == FROM_PROC) ? SELF : se->req_endpt;
/* read set */
src_fds = (direction == FROM_PROC) ? se->vir_readfds : &se->ready_readfds;
dst_fds = (direction == FROM_PROC) ? &se->readfds : se->vir_readfds;
if (se->vir_readfds) {
r = sys_vircopy(src_e, D, (vir_bytes) src_fds, dst_e, D,
(vir_bytes) dst_fds, fd_setsize);
if (r != OK) return(r);
}
/* write set */
src_fds = (direction == FROM_PROC) ? se->vir_writefds : &se->ready_writefds;
dst_fds = (direction == FROM_PROC) ? &se->writefds : se->vir_writefds;
if (se->vir_writefds) {
r = sys_vircopy(src_e, D, (vir_bytes) src_fds, dst_e, D,
(vir_bytes) dst_fds, fd_setsize);
if (r != OK) return(r);
}
/* error set */
src_fds = (direction == FROM_PROC) ? se->vir_errorfds : &se->ready_errorfds;
dst_fds = (direction == FROM_PROC) ? &se->errorfds : se->vir_errorfds;
if (se->vir_errorfds) {
r = sys_vircopy(src_e, D, (vir_bytes) src_fds, dst_e, D,
(vir_bytes) dst_fds, fd_setsize);
if (r != OK) return(r);
}
return(OK);
}
/*===========================================================================*
* select_cancel_all *
*===========================================================================*/
PRIVATE void select_cancel_all(struct selectentry *se)
{
/* Cancel select. Decrease select usage and cancel timer */
int fd;
struct filp *f;
for (fd = 0; fd < se->nfds; fd++) {
if ((f = se->filps[fd]) == NULL) continue;
se->filps[fd] = NULL;
select_cancel_filp(f);
}
if (se->expiry > 0) {
cancel_timer(&se->timer);
se->expiry = 0;
}
se->requestor = NULL;
}
/*===========================================================================*
* select_cancel_filp *
*===========================================================================*/
PRIVATE void select_cancel_filp(struct filp *f)
{
/* Reduce number of select users of this filp */
assert(f);
assert(f->filp_selectors >= 0);
if (f->filp_selectors == 0) return;
if (f->filp_count == 0) return;
select_lock_filp(f, f->filp_select_ops);
f->filp_selectors--;
if (f->filp_selectors == 0) {
/* No one selecting on this filp anymore, forget about select state */
f->filp_select_ops = 0;
f->filp_select_flags = 0;
f->filp_pipe_select_ops = 0;
}
unlock_filp(f);
}
/*===========================================================================*
* select_return *
*===========================================================================*/
PRIVATE void select_return(struct selectentry *se)
{
int r, r1;
assert(!is_deferred(se)); /* Not done yet, first wait for async reply */
select_cancel_all(se);
r1 = copy_fdsets(se, se->nfds, TO_PROC);
if (r1 != OK)
r = r1;
else if (se->error != OK)
r = se->error;
else
r = se->nreadyfds;
revive(se->req_endpt, r);
}
/*===========================================================================*
* select_callback *
*===========================================================================*/
PUBLIC void select_callback(struct filp *f, int status)
{
filp_status(f, status);
}
/*===========================================================================*
* init_select *
*===========================================================================*/
PUBLIC void init_select(void)
{
int s;
for (s = 0; s < MAXSELECTS; s++)
init_timer(&selecttab[s].timer);
}
/*===========================================================================*
* select_forget *
*===========================================================================*/
PUBLIC void select_forget(endpoint_t proc_e)
{
/* Something has happened (e.g. signal delivered that interrupts select()).
* Totally forget about the select(). */
int slot;
struct selectentry *se;
for (slot = 0; slot < MAXSELECTS; slot++) {
se = &selecttab[slot];
if (se->requestor != NULL && se->req_endpt == proc_e)
break;
}
if (slot >= MAXSELECTS) return; /* Entry not found */
se->error = EINTR;
if (is_deferred(se)) return; /* Still awaiting initial reply */
select_cancel_all(se);
}
/*===========================================================================*
* select_timeout_check *
*===========================================================================*/
PUBLIC void select_timeout_check(timer_t *timer)
{
int s;
struct selectentry *se;
s = tmr_arg(timer)->ta_int;
if (s < 0 || s >= MAXSELECTS) return; /* Entry does not exist */
se = &selecttab[s];
if (se->requestor == NULL) return;
fp = se->requestor;
if (se->expiry <= 0) return; /* Strange, did we even ask for a timeout? */
se->expiry = 0;
if (is_deferred(se)) return; /* Wait for initial replies to DEV_SELECT */
select_return(se);
}
/*===========================================================================*
* select_unsuspend_by_endpt *
*===========================================================================*/
PUBLIC void select_unsuspend_by_endpt(endpoint_t proc_e)
{
/* Revive blocked processes when a driver has disappeared */
int fd, s, major;
struct selectentry *se;
struct filp *f;
for (s = 0; s < MAXSELECTS; s++) {
int wakehim = 0;
se = &selecttab[s];
if (se->requestor == NULL) continue;
if (se->requestor->fp_endpoint == proc_e) {
assert(se->requestor->fp_flags & FP_EXITING);
select_cancel_all(se);
continue;
}
for (fd = 0; fd < se->nfds; fd++) {
if ((f = se->filps[fd]) == NULL || f->filp_vno == NULL)
continue;
major = major(f->filp_vno->v_sdev);
if (dmap_driver_match(proc_e, major)) {
se->filps[fd] = NULL;
se->error = EINTR;
select_cancel_filp(f);
wakehim = 1;
}
}
if (wakehim && !is_deferred(se))
select_return(se);
}
}
/*===========================================================================*
* select_reply1 *
*===========================================================================*/
PUBLIC void select_reply1(driver_e, minor, status)
endpoint_t driver_e;
int minor;
int status;
{
/* Handle reply to DEV_SELECT request */
int major;
dev_t dev;
struct filp *f;
struct dmap *dp;
struct vnode *vp;
/* Figure out which device is replying */
if ((dp = get_dmap(driver_e)) == NULL) return;
major = dp-dmap;
dev = makedev(major, minor);
/* Get filp belonging to character special file */
if ((f = dp->dmap_sel_filp) == NULL) {
printf("VFS (%s:%d): major %d was not expecting a DEV_SELECT reply\n",
__FILE__, __LINE__, major);
return;
}
/* Is the filp still in use and busy waiting for a reply? The owner might
* have vanished before the driver was able to reply. */
if (f->filp_count >= 1 && (f->filp_select_flags & FSF_BUSY)) {
/* Find vnode and check we got a reply from the device we expected */
vp = f->filp_vno;
assert(vp != NULL);
assert((vp->v_mode & I_TYPE) == I_CHAR_SPECIAL); /* Must be char. special */
if (vp->v_sdev != dev) {
printf("VFS (%s:%d): expected reply from dev %d not %d\n",
__FILE__, __LINE__, vp->v_sdev, dev);
return;
}
}
/* No longer waiting for a reply from this device */
dp->dmap_sel_filp = NULL;
/* Process select result only if requestor is still around. That is, the
* corresponding filp is still in use.
*/
if (f->filp_count >= 1) {
select_lock_filp(f, f->filp_select_ops);
f->filp_select_flags &= ~FSF_BUSY;
/* The select call is done now, except when
* - another process started a select on the same filp with possibly a
* different set of operations.
* - a process does a select on the same filp but using different file
* descriptors.
* - the select has a timeout. Upon receiving this reply the operations
* might not be ready yet, so we want to wait for that to ultimately
* happen.
* Therefore we need to keep remembering what the operations are.
*/
if (!(f->filp_select_flags & (FSF_UPDATE|FSF_BLOCKED)))
f->filp_select_ops = 0; /* done selecting */
else if (!(f->filp_select_flags & FSF_UPDATE))
/* there may be operations pending */
f->filp_select_ops &= ~status;
/* Tell filp owners about result unless we need to wait longer */
if (!(status == 0 && (f->filp_select_flags & FSF_BLOCKED))) {
if (status > 0) { /* operations ready */
if (status & SEL_RD)
f->filp_select_flags &= ~FSF_RD_BLOCK;
if (status & SEL_WR)
f->filp_select_flags &= ~FSF_WR_BLOCK;
if (status & SEL_ERR)
f->filp_select_flags &= ~FSF_ERR_BLOCK;
} else if (status < 0) { /* error */
/* Always unblock upon error */
f->filp_select_flags &= ~FSF_BLOCKED;
}
unlock_filp(f);
filp_status(f, status); /* Tell filp owners about the results */
} else {
unlock_filp(f);
}
}
select_restart_filps();
}
/*===========================================================================*
* select_reply2 *
*===========================================================================*/
PUBLIC void select_reply2(driver_e, minor, status)
endpoint_t driver_e;
int minor;
int status;
{
/* Handle secondary reply to DEV_SELECT request. A secondary reply occurs when
* the select request is 'blocking' until an operation becomes ready. */
int major, slot, fd;
dev_t dev;
struct filp *f;
struct dmap *dp;
struct vnode *vp;
struct selectentry *se;
if (status == 0) {
printf("VFS (%s:%d): weird status (%d) to report\n",
__FILE__, __LINE__, status);
return;
}
/* Figure out which device is replying */
if ((dp = get_dmap(driver_e)) == NULL) {
printf("VFS (%s:%d): endpoint %d is not a known driver endpoint\n",
__FILE__, __LINE__, driver_e);
return;
}
major = dp-dmap;
dev = makedev(major, minor);
/* Find all file descriptors selecting for this device */
for (slot = 0; slot < MAXSELECTS; slot++) {
se = &selecttab[slot];
if (se->requestor == NULL) continue; /* empty slot */
for (fd = 0; fd < se->nfds; fd++) {
if ((f = se->filps[fd]) == NULL) continue;
if ((vp = f->filp_vno) == NULL) continue;
if ((vp->v_mode & I_TYPE) != I_CHAR_SPECIAL) continue;
if (vp->v_sdev != dev) continue;
select_lock_filp(f, f->filp_select_ops);
if (status > 0) { /* Operations ready */
/* Clear the replied bits from the request
* mask unless FSF_UPDATE is set.
*/
if (!(f->filp_select_flags & FSF_UPDATE))
f->filp_select_ops &= ~status;
if (status & SEL_RD)
f->filp_select_flags &= ~FSF_RD_BLOCK;
if (status & SEL_WR)
f->filp_select_flags &= ~FSF_WR_BLOCK;
if (status & SEL_ERR)
f->filp_select_flags &= ~FSF_ERR_BLOCK;
ops2tab(status, fd, se);
} else {
f->filp_select_flags &= ~FSF_BLOCKED;
ops2tab(SEL_RD|SEL_WR|SEL_ERR, fd, se);
}
unlock_filp(f);
if (se->nreadyfds > 0) restart_proc(se);
}
}
select_restart_filps();
}
/*===========================================================================*
* select_restart_filps *
*===========================================================================*/
PRIVATE void select_restart_filps()
{
int fd, slot;
struct filp *f;
struct vnode *vp;
struct selectentry *se;
/* Locate filps that can be restarted */
for (slot = 0; slot < MAXSELECTS; slot++) {
se = &selecttab[slot];
if (se->requestor == NULL) continue; /* empty slot */
/* Only 'deferred' processes are eligible to restart */
if (!is_deferred(se)) continue;
/* Find filps that are not waiting for a reply, but have an updated
* status (i.e., another select on the same filp with possibly a
* different set of operations is to be done), and thus requires the
* select request to be sent again).
*/
for (fd = 0; fd < se->nfds; fd++) {
int r, wantops, ops;
if ((f = se->filps[fd]) == NULL) continue;
if (f->filp_select_flags & FSF_BUSY) /* Still waiting for */
continue; /* initial reply */
if (!(f->filp_select_flags & FSF_UPDATE)) /* Must be in */
continue; /* 'update' state */
wantops = ops = f->filp_select_ops;
select_lock_filp(f, ops);
vp = f->filp_vno;
assert((vp->v_mode & I_TYPE) == I_CHAR_SPECIAL);
r = do_select_request(se, fd, &wantops);
unlock_filp(f);
if (r != SEL_OK) {
if (r == SEL_DEFERRED) continue;
else break; /* Error or bogus return code; abort */
}
if (wantops & ops) ops2tab(wantops, fd, se);
}
}
}
/*===========================================================================*
* do_select_request *
*===========================================================================*/
PRIVATE int do_select_request(se, fd, ops)
struct selectentry *se;
int fd;
int *ops;
{
/* Perform actual select request for file descriptor fd */
int r, type;
struct filp *f;
type = se->type[fd];
f = se->filps[fd];
r = fdtypes[type].select_request(f, ops, se->block);
if (r != SEL_OK && r != SEL_DEFERRED) {
se->error = EINTR;
se->block = 0; /* Stop blocking to return asap */
if (!is_deferred(se)) select_cancel_all(se);
}
return(r);
}
/*===========================================================================*
* filp_status *
*===========================================================================*/
PRIVATE void filp_status(f, status)
struct filp *f;
int status;
{
/* Tell processes that need to know about the status of this filp */
int fd, slot;
struct selectentry *se;
for (slot = 0; slot < MAXSELECTS; slot++) {
se = &selecttab[slot];
if (se->requestor == NULL) continue; /* empty slot */
for (fd = 0; fd < se->nfds; fd++) {
if (se->filps[fd] != f) continue;
if (status < 0)
ops2tab(SEL_RD|SEL_WR|SEL_ERR, fd, se);
else
ops2tab(status, fd, se);
restart_proc(se);
}
}
}
/*===========================================================================*
* restart_proc *
*===========================================================================*/
PRIVATE void restart_proc(se)
struct selectentry *se;
{
/* Tell process about select results (if any) unless there are still results
* pending. */
if ((se->nreadyfds > 0 || !se->block) && !is_deferred(se))
select_return(se);
}
/*===========================================================================*
* wipe_select *
*===========================================================================*/
PRIVATE void wipe_select(struct selectentry *se)
{
se->nfds = 0;
se->nreadyfds = 0;
se->error = OK;
se->block = 0;
memset(se->filps, 0, sizeof(se->filps));
FD_ZERO(&se->readfds);
FD_ZERO(&se->writefds);
FD_ZERO(&se->errorfds);
FD_ZERO(&se->ready_readfds);
FD_ZERO(&se->ready_writefds);
FD_ZERO(&se->ready_errorfds);
}
/*===========================================================================*
* select_lock_filp *
*===========================================================================*/
PRIVATE void select_lock_filp(struct filp *f, int ops)
{
/* Lock a filp and vnode based on which operations are requested */
tll_access_t locktype;;
locktype = VNODE_READ; /* By default */
if (ops & (SEL_WR|SEL_ERR))
/* Selecting for error or writing requires exclusive access */
locktype = VNODE_WRITE;
lock_filp(f, locktype);
}
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