forked from Minki/linux
tty: Move parts of tty_init_dev into new functions
Move the 'find-tty' and 'fast-track-open' parts of init_dev() to separate functions. Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com> Signed-off-by: Alan Cox <alan@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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d81ed10307
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2349970575
@ -1204,6 +1204,80 @@ static void tty_line_name(struct tty_driver *driver, int index, char *p)
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sprintf(p, "%s%d", driver->name, index + driver->name_base);
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}
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/*
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* find_tty() - find an existing tty, if any
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* @driver: the driver for the tty
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* @idx: the minor number
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*
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* Return the tty, if found or ERR_PTR() otherwise.
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*
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* Locking: tty_mutex must be held. If tty is found, the mutex must
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* be held until the 'fast-open' is also done.
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*/
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struct tty_struct *find_tty(struct tty_driver *driver, int idx)
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{
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struct tty_struct *tty;
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/* check whether we're reopening an existing tty */
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if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
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tty = devpts_get_tty(idx);
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/*
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* If we don't have a tty here on a slave open, it's because
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* the master already started the close process and there's
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* no relation between devpts file and tty anymore.
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*/
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if (!tty && driver->subtype == PTY_TYPE_SLAVE)
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return ERR_PTR(-EIO);
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/*
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* tty is safe on because we are called with tty_mutex held
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* and release_dev() won't change tty->count or tty->flags
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* without grabbing tty_mutex.
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*/
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if (tty && driver->subtype == PTY_TYPE_MASTER)
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tty = tty->link;
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} else
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tty = driver->ttys[idx];
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return tty;
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}
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/*
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* fast_tty_open() - fast re-open of an open tty
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* @tty - the tty to open
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*
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* Return 0 on success, -errno on error.
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*
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* Locking: tty_mutex must be held from the time the tty was found
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* till this open completes.
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*/
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static int fast_tty_open(struct tty_struct *tty)
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{
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struct tty_driver *driver = tty->driver;
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if (test_bit(TTY_CLOSING, &tty->flags))
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return -EIO;
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if (driver->type == TTY_DRIVER_TYPE_PTY &&
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driver->subtype == PTY_TYPE_MASTER) {
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/*
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* special case for PTY masters: only one open permitted,
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* and the slave side open count is incremented as well.
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*/
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if (tty->count)
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return -EIO;
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tty->link->count++;
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}
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tty->count++;
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tty->driver = driver; /* N.B. why do this every time?? */
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/* FIXME */
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if (!test_bit(TTY_LDISC, &tty->flags))
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printk(KERN_ERR "fast_tty_open: no ldisc\n");
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return 0;
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}
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/**
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* tty_init_dev - initialise a tty device
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* @driver: tty driver we are opening a device on
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@ -1238,29 +1312,21 @@ int tty_init_dev(struct tty_driver *driver, int idx,
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int retval = 0;
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/* check whether we're reopening an existing tty */
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if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
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tty = devpts_get_tty(idx);
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/*
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* If we don't have a tty here on a slave open, it's because
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* the master already started the close process and there's
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* no relation between devpts file and tty anymore.
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*/
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if (!tty && driver->subtype == PTY_TYPE_SLAVE) {
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retval = -EIO;
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goto end_init;
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}
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/*
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* It's safe from now on because tty_init_dev() is called with
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* tty_mutex held and tty_release_dev() won't change tty->count
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* or tty->flags without having to grab tty_mutex
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*/
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if (tty && driver->subtype == PTY_TYPE_MASTER)
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tty = tty->link;
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} else {
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tty = driver->ttys[idx];
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tty = find_tty(driver, idx);
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if (IS_ERR(tty)) {
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retval = PTR_ERR(tty);
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goto end_init;
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}
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if (tty) goto fast_track;
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if (tty) {
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retval = fast_tty_open(tty);
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if (retval)
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return retval;
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*ret_tty = tty;
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return 0;
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}
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/* Check if pty master is being opened multiple times */
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if (driver->subtype == PTY_TYPE_MASTER &&
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(driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
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retval = -EIO;
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@ -1400,37 +1466,6 @@ int tty_init_dev(struct tty_driver *driver, int idx,
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if (retval)
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goto release_mem_out;
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goto success;
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/*
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* This fast open can be used if the tty is already open.
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* No memory is allocated, and the only failures are from
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* attempting to open a closing tty or attempting multiple
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* opens on a pty master.
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*/
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fast_track:
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if (test_bit(TTY_CLOSING, &tty->flags)) {
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retval = -EIO;
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goto end_init;
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}
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if (driver->type == TTY_DRIVER_TYPE_PTY &&
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driver->subtype == PTY_TYPE_MASTER) {
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/*
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* special case for PTY masters: only one open permitted,
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* and the slave side open count is incremented as well.
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*/
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if (tty->count) {
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retval = -EIO;
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goto end_init;
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}
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tty->link->count++;
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}
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tty->count++;
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tty->driver = driver; /* N.B. why do this every time?? */
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/* FIXME */
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if (!test_bit(TTY_LDISC, &tty->flags))
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printk(KERN_ERR "tty_init_dev but no ldisc\n");
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success:
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*ret_tty = tty;
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