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minix/servers/vfs/select.c
David van Moolenbroek b003ed0929 UDS: split off from PFS 
Change-Id: I769cbd64aa6e5e85a797caf0f8bbb4c20e145263
2014-03-01 09:04:57 +01:00

1073 lines
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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
*
* The select code uses minimal locking, so that the replies from character
* drivers can be processed without blocking. Filps are locked only for pipes.
* We make the assumption that any other structures and fields are safe to
* check (and possibly change) as long as we know that a process is blocked on
* a select(2) call, meaning that all involved filps are guaranteed to stay
* open until either we finish the select call, it the process gets interrupted
* by a signal.
*/
#include "fs.h"
#include <sys/fcntl.h>
#include <sys/time.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <string.h>
#include <assert.h>
#include "file.h"
#include "vnode.h"
/* max. number of simultaneously pending select() calls */
#define MAXSELECTS 25
#define FROM_PROC 0
#define TO_PROC 1
static 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;
char starting;
clock_t expiry;
minix_timer_t timer; /* if expiry > 0 */
} selecttab[MAXSELECTS];
static int copy_fdsets(struct selectentry *se, int nfds, int direction);
static void filp_status(struct filp *fp, int status);
static int is_deferred(struct selectentry *se);
static void restart_proc(struct selectentry *se);
static void ops2tab(int ops, int fd, struct selectentry *e);
static int is_regular_file(struct filp *f);
static int is_pipe(struct filp *f);
static int is_char_device(struct filp *f);
static void select_lock_filp(struct filp *f, int ops);
static int select_request_file(struct filp *f, int *ops, int block);
static int select_request_char(struct filp *f, int *ops, int block);
static int select_request_pipe(struct filp *f, int *ops, int block);
static void select_cancel_all(struct selectentry *e);
static void select_cancel_filp(struct filp *f);
static void select_return(struct selectentry *);
static void select_restart_filps(void);
static int tab2ops(int fd, struct selectentry *e);
static void wipe_select(struct selectentry *s);
static struct fdtype {
int (*select_request)(struct filp *, int *ops, int block);
int (*type_match)(struct filp *f);
} fdtypes[] = {
{ select_request_char, is_char_device },
{ select_request_file, is_regular_file },
{ select_request_pipe, is_pipe },
};
#define SEL_FDS (sizeof(fdtypes) / sizeof(fdtypes[0]))
/*===========================================================================*
* do_select *
*===========================================================================*/
int do_select(message *UNUSED(m_out))
{
/* 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 off
* 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 filp *f;
unsigned int type, ops;
struct timeval timeout;
struct selectentry *se;
vir_bytes vtimeout;
nfds = job_m_in.SEL_NFDS;
vtimeout = (vir_bytes) job_m_in.SEL_TIMEOUT;
/* 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->requestor = fp;
se->req_endpt = who_e;
se->vir_readfds = (fd_set *) job_m_in.SEL_READFDS;
se->vir_writefds = (fd_set *) job_m_in.SEL_WRITEFDS;
se->vir_errorfds = (fd_set *) job_m_in.SEL_ERRORFDS;
/* Copy fdsets from the process */
if ((r = copy_fdsets(se, nfds, FROM_PROC)) != OK) {
se->requestor = NULL;
return(r);
}
/* Did the process set a timeout value? If so, retrieve it. */
if (vtimeout != 0) {
do_timeout = 1;
r = sys_vircopy(who_e, (vir_bytes) vtimeout, SELF,
(vir_bytes) &timeout, sizeof(timeout));
if (r != OK) {
se->requestor = NULL;
return(r);
}
}
/* No nonsense in the timeval */
if (do_timeout && (timeout.tv_sec < 0 || timeout.tv_usec < 0)) {
se->requestor = NULL;
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) */
/* We are going to lock filps, and that means that while locking a second
* filp, we might already get the results for the first one. In that case,
* the incoming results must not cause the select call to finish prematurely.
*/
se->starting = TRUE;
/* Verify that file descriptors are okay to select on */
for (fd = 0; fd < nfds; fd++) {
/* 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;
se->requestor = NULL;
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
* UDS major (socket type AF_UNIX). Additionally, we give other
* character drivers the chance to handle select for any of their
* device nodes. Some may not implement support for select and let
* libchardriver return EBADF, which we then pass to the calling
* process once we receive the reply.
*/
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 */
se->requestor = NULL;
return(EBADF);
}
}
/* Check all file descriptors in the set whether one is 'ready' now */
for (fd = 0; fd < nfds; fd++) {
/* Again, check for involuntarily selected fd's */
if (!(ops = tab2ops(fd, se)))
continue; /* No operations set; nothing to do for this fd */
/* File descriptors selected for reading that are not opened for
* reading should be marked as readable, as read calls would fail
* immediately. The same applies to writing.
*/
f = se->filps[fd];
if ((ops & SEL_RD) && !(f->filp_mode & R_BIT)) {
ops2tab(SEL_RD, fd, se);
ops &= ~SEL_RD;
}
if ((ops & SEL_WR) && !(f->filp_mode & W_BIT)) {
ops2tab(SEL_WR, fd, se);
ops &= ~SEL_WR;
}
/* Test filp for select operations if not already done so. e.g.,
* processes sharing a filp and both doing a select on that filp. */
if ((f->filp_select_ops & ops) != ops) {
int wantops;
wantops = (f->filp_select_ops |= ops);
type = se->type[fd];
select_lock_filp(f, wantops);
r = fdtypes[type].select_request(f, &wantops, se->block);
unlock_filp(f);
if (r != OK && r != SUSPEND) {
se->error = r;
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);
}
}
/* At this point there won't be any blocking calls anymore. */
se->starting = FALSE;
if ((se->nreadyfds > 0 || se->error != OK || !se->block) &&
!is_deferred(se)) {
/* An error occurred, or fd's were found that were ready to go right
* away, and/or we were instructed not to block at all. Must return
* immediately. Do not copy FD sets if an error occurred.
*/
if (se->error != OK)
r = se->error;
else
r = copy_fdsets(se, se->nfds, TO_PROC);
select_cancel_all(se);
se->requestor = NULL;
if (r != OK)
return(r);
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);
}
/* process now blocked */
suspend(FP_BLOCKED_ON_SELECT);
return(SUSPEND);
}
/*===========================================================================*
* is_deferred *
*===========================================================================*/
static int is_deferred(struct selectentry *se)
{
/* Find out whether this select has pending initial replies */
int fd;
struct filp *f;
/* The select call must have finished its initialization at all. */
if (se->starting) return(TRUE);
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 *
*===========================================================================*/
static int is_regular_file(struct filp *f)
{
return(f && f->filp_vno && S_ISREG(f->filp_vno->v_mode));
}
/*===========================================================================*
* is_pipe *
*===========================================================================*/
static int is_pipe(struct filp *f)
{
/* Recognize either anonymous pipe or named pipe (FIFO) */
return(f && f->filp_vno && S_ISFIFO(f->filp_vno->v_mode));
}
/*===========================================================================*
* is_char_device *
*===========================================================================*/
static int is_char_device(struct filp *f)
{
/* See if this filp is a handle on a character device. This function MUST NOT
* block its calling thread. The given filp may or may not be locked.
*/
return (f && f->filp_vno && S_ISCHR(f->filp_vno->v_mode));
}
/*===========================================================================*
* select_request_char *
*===========================================================================*/
static int select_request_char(struct filp *f, int *ops, int block)
{
/* Check readiness status on a character device. Unless suitable results are
* available right now, this will only initiate the polling process, causing
* result processing to be deferred. This function MUST NOT block its calling
* thread. The given filp may or may not be locked.
*/
int r, rops, major;
struct dmap *dp;
major = major(f->filp_vno->v_sdev);
if (major < 0 || major >= NR_DEVICES) return(ENXIO);
rops = *ops;
/* By default, nothing to do */
*ops = 0;
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)))
return(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(SUSPEND);
dp = &dmap[major];
if (dp->dmap_sel_busy)
return(SUSPEND);
f->filp_select_flags &= ~FSF_UPDATE;
r = cdev_select(f->filp_vno->v_sdev, rops);
if (r != OK)
return(r);
dp->dmap_sel_busy = TRUE;
dp->dmap_sel_filp = f;
f->filp_select_flags |= FSF_BUSY;
return(SUSPEND);
}
/*===========================================================================*
* select_request_file *
*===========================================================================*/
static 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(OK);
}
/*===========================================================================*
* select_request_pipe *
*===========================================================================*/
static int select_request_pipe(struct filp *f, int *ops, int block)
{
/* Check readiness status on a pipe. The given filp is locked. This function
* may block its calling thread if necessary.
*/
int orig_ops, r = 0, err;
orig_ops = *ops;
if ((*ops & (SEL_RD|SEL_ERR))) {
/* Check if we can read 1 byte */
err = pipe_check(f, READING, f->filp_flags & ~O_NONBLOCK, 1,
1 /* Check only */);
if (err != SUSPEND)
r |= SEL_RD;
if (err < 0 && err != SUSPEND)
r |= SEL_ERR;
}
if ((*ops & (SEL_WR|SEL_ERR))) {
/* Check if we can write 1 byte */
err = pipe_check(f, WRITING, f->filp_flags & ~O_NONBLOCK, 1,
1 /* Check only */);
if (err != SUSPEND)
r |= SEL_WR;
if (err < 0 && err != SUSPEND)
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(OK);
}
/*===========================================================================*
* tab2ops *
*===========================================================================*/
static 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 *
*===========================================================================*/
static 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 *
*===========================================================================*/
static int copy_fdsets(struct selectentry *se, int nfds, int direction)
{
/* Copy FD sets from or to the user process calling select(2). This function
* MUST NOT block the calling thread.
*/
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. */
fd_setsize = (size_t) (howmany(nfds, __NFDBITS) * sizeof(__fd_mask));
/* 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, (vir_bytes) src_fds, dst_e,
(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, (vir_bytes) src_fds, dst_e,
(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, (vir_bytes) src_fds, dst_e,
(vir_bytes) dst_fds, fd_setsize);
if (r != OK) return(r);
}
return(OK);
}
/*===========================================================================*
* select_cancel_all *
*===========================================================================*/
static void select_cancel_all(struct selectentry *se)
{
/* Cancel select, possibly on success. Decrease select usage and cancel timer.
* This function MUST NOT block its calling thread.
*/
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 *
*===========================================================================*/
static void select_cancel_filp(struct filp *f)
{
/* Reduce the number of select users of this filp. This function MUST NOT block
* its calling thread.
*/
dev_t major;
assert(f);
assert(f->filp_selectors > 0);
assert(f->filp_count > 0);
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;
/* If this filp is the subject of an ongoing select query to a
* character device, mark the query as stale, so that this filp will
* not be checked when the result arrives.
*/
if (is_char_device(f)) {
major = major(f->filp_vno->v_sdev);
if (dmap[major].dmap_sel_busy &&
dmap[major].dmap_sel_filp == f)
dmap[major].dmap_sel_filp = NULL; /* leave _busy set */
}
}
}
/*===========================================================================*
* select_return *
*===========================================================================*/
static void select_return(struct selectentry *se)
{
/* Return the results of a select call to the user process and revive the
* process. This function MUST NOT block its calling thread.
*/
int r;
assert(!is_deferred(se)); /* Not done yet, first wait for async reply */
select_cancel_all(se);
if (se->error != OK)
r = se->error;
else
r = copy_fdsets(se, se->nfds, TO_PROC);
if (r == OK)
r = se->nreadyfds;
revive(se->req_endpt, r);
}
/*===========================================================================*
* select_callback *
*===========================================================================*/
void select_callback(struct filp *f, int status)
{
/* The status of a filp has changed, with the given ready operations or error.
* This function is currently called only for pipes, and holds the lock to
* the filp.
*/
filp_status(f, status);
}
/*===========================================================================*
* init_select *
*===========================================================================*/
void init_select(void)
{
int s;
for (s = 0; s < MAXSELECTS; s++)
init_timer(&selecttab[s].timer);
}
/*===========================================================================*
* select_forget *
*===========================================================================*/
void select_forget(void)
{
/* The calling thread's associated process is expected to be unpaused, due to
* a signal that is supposed to interrupt the current system call. Totally
* forget about the select(). This function may block its calling thread if
* necessary (but it doesn't).
*/
int slot;
struct selectentry *se;
for (slot = 0; slot < MAXSELECTS; slot++) {
se = &selecttab[slot];
if (se->requestor == fp)
break;
}
if (slot >= MAXSELECTS) return; /* Entry not found */
assert(se->starting == FALSE);
/* Do NOT test on is_deferred here. We can safely cancel ongoing queries. */
select_cancel_all(se);
}
/*===========================================================================*
* select_timeout_check *
*===========================================================================*/
void select_timeout_check(minix_timer_t *timer)
{
/* An alarm has gone off for one of the select queries. This function MUST NOT
* block its calling thread.
*/
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;
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 CDEV_SELECT */
select_return(se);
}
/*===========================================================================*
* select_unsuspend_by_endpt *
*===========================================================================*/
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 = EIO;
select_cancel_filp(f);
wakehim = 1;
}
}
if (wakehim && !is_deferred(se))
select_return(se);
}
}
/*===========================================================================*
* select_reply1 *
*===========================================================================*/
void select_reply1(driver_e, minor, status)
endpoint_t driver_e;
int minor;
int status;
{
/* Handle the initial reply to CDEV_SELECT request. This function MUST NOT
* block its calling thread.
*/
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 (!dp->dmap_sel_busy) {
printf("VFS (%s:%d): major %d was not expecting a CDEV_SELECT reply\n",
__FILE__, __LINE__, major);
return;
}
/* The select filp may have been set to NULL if the requestor has been
* unpaused in the meantime. In that case, we ignore the result, but we do
* look for other filps to restart later.
*/
if ((f = dp->dmap_sel_filp) != NULL) {
/* Find vnode and check we got a reply from the device we expected */
vp = f->filp_vno;
assert(vp != NULL);
assert(S_ISCHR(vp->v_mode));
if (vp->v_sdev != dev) {
/* This should never happen. The driver may be misbehaving.
* For now we assume that the reply we want will arrive later..
*/
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_busy = FALSE;
dp->dmap_sel_filp = NULL;
/* Process the select result only if the filp is valid. */
if (f != NULL) {
assert(f->filp_count >= 1);
assert(f->filp_select_flags & FSF_BUSY);
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 (status > 0 && !(f->filp_select_flags & FSF_UPDATE))
/* there may be operations pending */
f->filp_select_ops &= ~status;
/* Record new filp status */
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;
}
}
filp_status(f, status); /* Tell filp owners about the results */
}
select_restart_filps();
}
/*===========================================================================*
* select_reply2 *
*===========================================================================*/
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. This
* function MUST NOT block its calling thread.
*/
int major, slot, found, 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 */
found = FALSE;
for (fd = 0; fd < se->nfds; fd++) {
if ((f = se->filps[fd]) == NULL) continue;
if ((vp = f->filp_vno) == NULL) continue;
if (!S_ISCHR(vp->v_mode)) continue;
if (vp->v_sdev != dev) continue;
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;
se->error = status;
}
found = TRUE;
}
/* Even if 'found' is set now, nothing may have changed for this call,
* as it may not have been interested in the operations that were
* reported as ready. Let restart_proc check.
*/
if (found)
restart_proc(se);
}
select_restart_filps();
}
/*===========================================================================*
* select_restart_filps *
*===========================================================================*/
static void select_restart_filps(void)
{
/* We got a result from a character driver, and now we need to check if we can
* restart deferred polling operations. This function MUST NOT block its
* calling thread.
*/
int fd, slot;
struct filp *f;
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 */
/* This function is suitable only for character devices. In
* particular, checking pipes the same way would introduce a
* serious locking problem.
*/
assert(is_char_device(f));
wantops = ops = f->filp_select_ops;
r = select_request_char(f, &wantops, se->block);
if (r != OK && r != SUSPEND) {
se->error = r;
restart_proc(se);
break; /* Error or bogus return code; abort */
}
if (wantops & ops) ops2tab(wantops, fd, se);
}
}
}
/*===========================================================================*
* filp_status *
*===========================================================================*/
static void filp_status(f, status)
struct filp *f;
int status;
{
/* Tell processes that need to know about the status of this filp. This
* function MUST NOT block its calling thread.
*/
int fd, slot, found;
struct selectentry *se;
for (slot = 0; slot < MAXSELECTS; slot++) {
se = &selecttab[slot];
if (se->requestor == NULL) continue; /* empty slot */
found = FALSE;
for (fd = 0; fd < se->nfds; fd++) {
if (se->filps[fd] != f) continue;
if (status < 0)
se->error = status;
else
ops2tab(status, fd, se);
found = TRUE;
}
if (found)
restart_proc(se);
}
}
/*===========================================================================*
* restart_proc *
*===========================================================================*/
static void restart_proc(se)
struct selectentry *se;
{
/* Tell process about select results (if any) unless there are still results
* pending. This function MUST NOT block its calling thread.
*/
if ((se->nreadyfds > 0 || se->error != OK || !se->block) && !is_deferred(se))
select_return(se);
}
/*===========================================================================*
* wipe_select *
*===========================================================================*/
static 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 *
*===========================================================================*/
static void select_lock_filp(struct filp *f, int ops)
{
/* Lock a filp and vnode based on which operations are requested. This function
* may block its calling thread, obviously.
*/
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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