diff options
| -rw-r--r-- | drivers/bluetooth/hci_ldisc.c | 4 | ||||
| -rw-r--r-- | drivers/char/cyclades.c | 2 | ||||
| -rw-r--r-- | drivers/char/epca.c | 4 | ||||
| -rw-r--r-- | drivers/char/ip2/i2lib.c | 4 | ||||
| -rw-r--r-- | drivers/char/ip2/ip2main.c | 4 | ||||
| -rw-r--r-- | drivers/char/n_hdlc.c | 4 | ||||
| -rw-r--r-- | drivers/char/pty.c | 10 | ||||
| -rw-r--r-- | drivers/char/selection.c | 2 | ||||
| -rw-r--r-- | drivers/char/tty_io.c | 64 | ||||
| -rw-r--r-- | drivers/char/tty_ldisc.c | 477 | ||||
| -rw-r--r-- | include/linux/tty.h | 9 |
11 files changed, 330 insertions, 254 deletions
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c index af761dc434f..68801512859 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -277,8 +277,8 @@ static int hci_uart_tty_open(struct tty_struct *tty) /* FIXME: why is this needed. Note don't use ldisc_ref here as the open path is before the ldisc is referencable */ - if (tty->ldisc.ops->flush_buffer) - tty->ldisc.ops->flush_buffer(tty); + if (tty->ldisc->ops->flush_buffer) + tty->ldisc->ops->flush_buffer(tty); tty_driver_flush_buffer(tty); return 0; diff --git a/drivers/char/cyclades.c b/drivers/char/cyclades.c index 45601905174..f3366d3f06c 100644 --- a/drivers/char/cyclades.c +++ b/drivers/char/cyclades.c @@ -5200,7 +5200,7 @@ static int cyclades_proc_show(struct seq_file *m, void *v) (cur_jifs - info->idle_stats.recv_idle)/ HZ, info->idle_stats.overruns, /* FIXME: double check locking */ - (long)info->port.tty->ldisc.ops->num); + (long)info->port.tty->ldisc->ops->num); else seq_printf(m, "%3d %8lu %10lu %8lu " "%10lu %8lu %9lu %6ld\n", diff --git a/drivers/char/epca.c b/drivers/char/epca.c index 710ee933305..abef1f7d84f 100644 --- a/drivers/char/epca.c +++ b/drivers/char/epca.c @@ -2114,8 +2114,8 @@ static int pc_ioctl(struct tty_struct *tty, struct file *file, tty_wait_until_sent(tty, 0); } else { /* ldisc lock already held in ioctl */ - if (tty->ldisc.ops->flush_buffer) - tty->ldisc.ops->flush_buffer(tty); + if (tty->ldisc->ops->flush_buffer) + tty->ldisc->ops->flush_buffer(tty); } unlock_kernel(); /* Fall Thru */ diff --git a/drivers/char/ip2/i2lib.c b/drivers/char/ip2/i2lib.c index 0061e18aff6..0d10b89218e 100644 --- a/drivers/char/ip2/i2lib.c +++ b/drivers/char/ip2/i2lib.c @@ -868,11 +868,11 @@ i2Input(i2ChanStrPtr pCh) amountToMove = count; } // Move the first block - pCh->pTTY->ldisc.ops->receive_buf( pCh->pTTY, + pCh->pTTY->ldisc->ops->receive_buf( pCh->pTTY, &(pCh->Ibuf[stripIndex]), NULL, amountToMove ); // If we needed to wrap, do the second data move if (count > amountToMove) { - pCh->pTTY->ldisc.ops->receive_buf( pCh->pTTY, + pCh->pTTY->ldisc->ops->receive_buf( pCh->pTTY, pCh->Ibuf, NULL, count - amountToMove ); } // Bump and wrap the stripIndex all at once by the amount of data read. This diff --git a/drivers/char/ip2/ip2main.c b/drivers/char/ip2/ip2main.c index afd9247cf08..517271c762e 100644 --- a/drivers/char/ip2/ip2main.c +++ b/drivers/char/ip2/ip2main.c @@ -1315,8 +1315,8 @@ static inline void isig(int sig, struct tty_struct *tty, int flush) if (tty->pgrp) kill_pgrp(tty->pgrp, sig, 1); if (flush || !L_NOFLSH(tty)) { - if ( tty->ldisc.ops->flush_buffer ) - tty->ldisc.ops->flush_buffer(tty); + if ( tty->ldisc->ops->flush_buffer ) + tty->ldisc->ops->flush_buffer(tty); i2InputFlush( tty->driver_data ); } } diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c index bacb3e2872a..461ece591a5 100644 --- a/drivers/char/n_hdlc.c +++ b/drivers/char/n_hdlc.c @@ -342,8 +342,8 @@ static int n_hdlc_tty_open (struct tty_struct *tty) #endif /* Flush any pending characters in the driver and discipline. */ - if (tty->ldisc.ops->flush_buffer) - tty->ldisc.ops->flush_buffer(tty); + if (tty->ldisc->ops->flush_buffer) + tty->ldisc->ops->flush_buffer(tty); tty_driver_flush_buffer(tty); diff --git a/drivers/char/pty.c b/drivers/char/pty.c index da2cb8c70c1..5acd29e6e04 100644 --- a/drivers/char/pty.c +++ b/drivers/char/pty.c @@ -110,7 +110,7 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, c = to->receive_room; if (c > count) c = count; - to->ldisc.ops->receive_buf(to, buf, NULL, c); + to->ldisc->ops->receive_buf(to, buf, NULL, c); return c; } @@ -148,11 +148,11 @@ static int pty_chars_in_buffer(struct tty_struct *tty) int count; /* We should get the line discipline lock for "tty->link" */ - if (!to || !to->ldisc.ops->chars_in_buffer) + if (!to || !to->ldisc->ops->chars_in_buffer) return 0; /* The ldisc must report 0 if no characters available to be read */ - count = to->ldisc.ops->chars_in_buffer(to); + count = to->ldisc->ops->chars_in_buffer(to); if (tty->driver->subtype == PTY_TYPE_SLAVE) return count; @@ -186,8 +186,8 @@ static void pty_flush_buffer(struct tty_struct *tty) if (!to) return; - if (to->ldisc.ops->flush_buffer) - to->ldisc.ops->flush_buffer(to); + if (to->ldisc->ops->flush_buffer) + to->ldisc->ops->flush_buffer(to); if (to->packet) { spin_lock_irqsave(&tty->ctrl_lock, flags); diff --git a/drivers/char/selection.c b/drivers/char/selection.c index cb8ca569896..f97b9e84806 100644 --- a/drivers/char/selection.c +++ b/drivers/char/selection.c @@ -327,7 +327,7 @@ int paste_selection(struct tty_struct *tty) } count = sel_buffer_lth - pasted; count = min(count, tty->receive_room); - tty->ldisc.ops->receive_buf(tty, sel_buffer + pasted, + tty->ldisc->ops->receive_buf(tty, sel_buffer + pasted, NULL, count); pasted += count; } diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index be49d0730bb..2f44b0b241c 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -492,22 +492,6 @@ void tty_ldisc_flush(struct tty_struct *tty) EXPORT_SYMBOL_GPL(tty_ldisc_flush); /** - * tty_reset_termios - reset terminal state - * @tty: tty to reset - * - * Restore a terminal to the driver default state - */ - -static void tty_reset_termios(struct tty_struct *tty) -{ - mutex_lock(&tty->termios_mutex); - *tty->termios = tty->driver->init_termios; - tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); - tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); - mutex_unlock(&tty->termios_mutex); -} - -/** * do_tty_hangup - actual handler for hangup events * @work: tty device * @@ -536,7 +520,6 @@ static void do_tty_hangup(struct work_struct *work) struct file *cons_filp = NULL; struct file *filp, *f = NULL; struct task_struct *p; - struct tty_ldisc *ld; int closecount = 0, n; unsigned long flags; int refs = 0; @@ -567,40 +550,8 @@ static void do_tty_hangup(struct work_struct *work) filp->f_op = &hung_up_tty_fops; } file_list_unlock(); - /* - * FIXME! What are the locking issues here? This may me overdoing - * things... This question is especially important now that we've - * removed the irqlock. - */ - ld = tty_ldisc_ref(tty); - if (ld != NULL) { - /* We may have no line discipline at this point */ - if (ld->ops->flush_buffer) - ld->ops->flush_buffer(tty); - tty_driver_flush_buffer(tty); - if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && - ld->ops->write_wakeup) - ld->ops->write_wakeup(tty); - if (ld->ops->hangup) - ld->ops->hangup(tty); - } - /* - * FIXME: Once we trust the LDISC code better we can wait here for - * ldisc completion and fix the driver call race - */ - wake_up_interruptible_poll(&tty->write_wait, POLLOUT); - wake_up_interruptible_poll(&tty->read_wait, POLLIN); - /* - * Shutdown the current line discipline, and reset it to - * N_TTY. - */ - if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) - tty_reset_termios(tty); - /* Defer ldisc switch */ - /* tty_deferred_ldisc_switch(N_TTY); - This should get done automatically when the port closes and - tty_release is called */ + tty_ldisc_hangup(tty); read_lock(&tasklist_lock); if (tty->session) { @@ -629,12 +580,15 @@ static void do_tty_hangup(struct work_struct *work) read_unlock(&tasklist_lock); spin_lock_irqsave(&tty->ctrl_lock, flags); - tty->flags = 0; + clear_bit(TTY_THROTTLED, &tty->flags); + clear_bit(TTY_PUSH, &tty->flags); + clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); put_pid(tty->session); put_pid(tty->pgrp); tty->session = NULL; tty->pgrp = NULL; tty->ctrl_status = 0; + set_bit(TTY_HUPPED, &tty->flags); spin_unlock_irqrestore(&tty->ctrl_lock, flags); /* Account for the p->signal references we killed */ @@ -660,10 +614,7 @@ static void do_tty_hangup(struct work_struct *work) * can't yet guarantee all that. */ set_bit(TTY_HUPPED, &tty->flags); - if (ld) { - tty_ldisc_enable(tty); - tty_ldisc_deref(ld); - } + tty_ldisc_enable(tty); unlock_kernel(); if (f) fput(f); @@ -2570,7 +2521,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case TIOCGSID: return tiocgsid(tty, real_tty, p); case TIOCGETD: - return put_user(tty->ldisc.ops->num, (int __user *)p); + return put_user(tty->ldisc->ops->num, (int __user *)p); case TIOCSETD: return tiocsetd(tty, p); /* @@ -2785,6 +2736,7 @@ void initialize_tty_struct(struct tty_struct *tty, tty->buf.head = tty->buf.tail = NULL; tty_buffer_init(tty); mutex_init(&tty->termios_mutex); + mutex_init(&tty->ldisc_mutex); init_waitqueue_head(&tty->write_wait); init_waitqueue_head(&tty->read_wait); INIT_WORK(&tty->hangup_work, do_tty_hangup); diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c index e3c6416aa86..a58a19a6a5e 100644 --- a/drivers/char/tty_ldisc.c +++ b/drivers/char/tty_ldisc.c @@ -115,19 +115,22 @@ EXPORT_SYMBOL(tty_unregister_ldisc); /** * tty_ldisc_try_get - try and reference an ldisc * @disc: ldisc number - * @ld: tty ldisc structure to complete * * Attempt to open and lock a line discipline into place. Return - * the line discipline refcounted and assigned in ld. On an error - * report the error code back + * the line discipline refcounted or an error. */ -static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld) +static struct tty_ldisc *tty_ldisc_try_get(int disc) { unsigned long flags; + struct tty_ldisc *ld; struct tty_ldisc_ops *ldops; int err = -EINVAL; + ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); + if (ld == NULL) + return ERR_PTR(-ENOMEM); + spin_lock_irqsave(&tty_ldisc_lock, flags); ld->ops = NULL; ldops = tty_ldiscs[disc]; @@ -140,17 +143,19 @@ static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld) /* lock it */ ldops->refcount++; ld->ops = ldops; + ld->refcount = 0; err = 0; } } spin_unlock_irqrestore(&tty_ldisc_lock, flags); - return err; + if (err) + return ERR_PTR(err); + return ld; } /** * tty_ldisc_get - take a reference to an ldisc * @disc: ldisc number - * @ld: tty line discipline structure to use * * Takes a reference to a line discipline. Deals with refcounts and * module locking counts. Returns NULL if the discipline is not available. @@ -161,44 +166,46 @@ static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld) * takes tty_ldisc_lock to guard against ldisc races */ -static int tty_ldisc_get(int disc, struct tty_ldisc *ld) +static struct tty_ldisc *tty_ldisc_get(int disc) { - int err; + struct tty_ldisc *ld; if (disc < N_TTY || disc >= NR_LDISCS) - return -EINVAL; - err = tty_ldisc_try_get(disc, ld); - if (err < 0) { + return ERR_PTR(-EINVAL); + ld = tty_ldisc_try_get(disc); + if (IS_ERR(ld)) { request_module("tty-ldisc-%d", disc); - err = tty_ldisc_try_get(disc, ld); + ld = tty_ldisc_try_get(disc); } - return err; + return ld; } /** * tty_ldisc_put - drop ldisc reference - * @disc: ldisc number + * @ld: ldisc * * Drop a reference to a line discipline. Manage refcounts and - * module usage counts + * module usage counts. Free the ldisc once the recount hits zero. * * Locking: * takes tty_ldisc_lock to guard against ldisc races */ -static void tty_ldisc_put(struct tty_ldisc_ops *ld) +static void tty_ldisc_put(struct tty_ldisc *ld) { unsigned long flags; - int disc = ld->num; + int disc = ld->ops->num; + struct tty_ldisc_ops *ldo; BUG_ON(disc < N_TTY || disc >= NR_LDISCS); spin_lock_irqsave(&tty_ldisc_lock, flags); - ld = tty_ldiscs[disc]; - BUG_ON(ld->refcount == 0); - ld->refcount--; - module_put(ld->owner); + ldo = tty_ldiscs[disc]; + BUG_ON(ldo->refcount == 0); + ldo->refcount--; + module_put(ldo->owner); spin_unlock_irqrestore(&tty_ldisc_lock, flags); + kfree(ld); } static void * tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) @@ -219,12 +226,13 @@ static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) static int tty_ldiscs_seq_show(struct seq_file *m, void *v) { int i = *(loff_t *)v; - struct tty_ldisc ld; + struct tty_ldisc *ld; - if (tty_ldisc_get(i, &ld) < 0) + ld = tty_ldisc_try_get(i); + if (IS_ERR(ld)) return 0; - seq_printf(m, "%-10s %2d\n", ld.ops->name ? ld.ops->name : "???", i); - tty_ldisc_put(ld.ops); + seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i); + tty_ldisc_put(ld); return 0; } @@ -263,8 +271,7 @@ const struct file_operations tty_ldiscs_proc_fops = { static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) { - ld->refcount = 0; - tty->ldisc = *ld; + tty->ldisc = ld; } /** @@ -286,7 +293,7 @@ static int tty_ldisc_try(struct tty_struct *tty) int ret = 0; spin_lock_irqsave(&tty_ldisc_lock, flags); - ld = &tty->ldisc; + ld = tty->ldisc; if (test_bit(TTY_LDISC, &tty->flags)) { ld->refcount++; ret = 1; @@ -315,8 +322,8 @@ struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) { /* wait_event is a macro */ wait_event(tty_ldisc_wait, tty_ldisc_try(tty)); - WARN_ON(tty->ldisc.refcount == 0); - return &tty->ldisc; + WARN_ON(tty->ldisc->refcount == 0); + return tty->ldisc; } EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); @@ -335,7 +342,7 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) { if (tty_ldisc_try(tty)) - return &tty->ldisc; + return tty->ldisc; return NULL; } @@ -407,6 +414,39 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num) mutex_unlock(&tty->termios_mutex); } +/** + * tty_ldisc_open - open a line discipline + * @tty: tty we are opening the ldisc on + * @ld: discipline to open + * + * A helper opening method. Also a convenient debugging and check + * point. + */ + +static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) +{ + WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); + if (ld->ops->open) + return ld->ops->open(tty); + return 0; +} + +/** + * tty_ldisc_close - close a line discipline + * @tty: tty we are opening the ldisc on + * @ld: discipline to close + * + * A helper close method. Also a convenient debugging and check + * point. + */ + +static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) +{ + WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); + clear_bit(TTY_LDISC_OPEN, &tty->flags); + if (ld->ops->close) + ld->ops->close(tty); +} /** * tty_ldisc_restore - helper for tty ldisc change @@ -420,31 +460,32 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num) static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) { char buf[64]; - struct tty_ldisc new_ldisc; + struct tty_ldisc *new_ldisc; + int r; /* There is an outstanding reference here so this is safe */ - tty_ldisc_get(old->ops->num, old); + old = tty_ldisc_get(old->ops->num); + WARN_ON(IS_ERR(old)); tty_ldisc_assign(tty, old); tty_set_termios_ldisc(tty, old->ops->num); - if (old->ops->open && (old->ops->open(tty) < 0)) { - tty_ldisc_put(old->ops); + if (tty_ldisc_open(tty, old) < 0) { + tty_ldisc_put(old); /* This driver is always present */ - if (tty_ldisc_get(N_TTY, &new_ldisc) < 0) + new_ldisc =tty_ldisc_get(N_TTY); + if (IS_ERR(new_ldisc)) panic("n_tty: get"); - tty_ldisc_assign(tty, &new_ldisc); + tty_ldisc_assign(tty, new_ldisc); tty_set_termios_ldisc(tty, N_TTY); - if (new_ldisc.ops->open) { - int r = new_ldisc.ops->open(tty); - if (r < 0) - panic("Couldn't open N_TTY ldisc for " - "%s --- error %d.", - tty_name(tty, buf), r); - } + r = tty_ldisc_open(tty, new_ldisc); + if (r < 0) + panic("Couldn't open N_TTY ldisc for " + "%s --- error %d.", + tty_name(tty, buf), r); } } /** - * tty_ldisc_halt - shutdown the line discipline + * tty_ldisc_halt - shut down the line discipline * @tty: tty device * * Shut down the line discipline and work queue for this tty device. @@ -456,14 +497,10 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) * tty_ldisc_wait_idle. */ -static void tty_ldisc_halt(struct tty_struct *tty) +static int tty_ldisc_halt(struct tty_struct *tty) { clear_bit(TTY_LDISC, &tty->flags); - cancel_delayed_work(&tty->buf.work); - /* - * Wait for ->hangup_work and ->buf.work handlers to terminate - */ - flush_scheduled_work(); + return cancel_delayed_work(&tty->buf.work); } /** @@ -473,18 +510,22 @@ static void tty_ldisc_halt(struct tty_struct *tty) * Wait for the line discipline to become idle. The discipline must * have been halted for this to guarantee it remains idle. * + * tty_ldisc_lock protects the ref counts currently. */ -static void tty_ldisc_wait_idle(struct tty_struct *tty) +static int tty_ldisc_wait_idle(struct tty_struct *tty) { unsigned long flags; spin_lock_irqsave(&tty_ldisc_lock, flags); - while (tty->ldisc.refcount) { + while (tty->ldisc->refcount) { spin_unlock_irqrestore(&tty_ldisc_lock, flags); - wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0); + if (wait_event_timeout(tty_ldisc_wait, + tty->ldisc->refcount == 0, 5 * HZ) == 0) + return -EBUSY; spin_lock_irqsave(&tty_ldisc_lock, flags); } spin_unlock_irqrestore(&tty_ldisc_lock, flags); + return 0; } /** @@ -493,39 +534,64 @@ static void tty_ldisc_wait_idle(struct tty_struct *tty) * @ldisc: the line discipline * * Set the discipline of a tty line. Must be called from a process - * context. + * context. The ldisc change logic has to protect itself against any + * overlapping ldisc change (including on the other end of pty pairs), + * the close of one side of a tty/pty pair, and eventually hangup. * - * Locking: takes tty_ldisc_lock. - * called functions take termios_mutex + * Locking: takes tty_ldisc_lock, termios_mutex */ int tty_set_ldisc(struct tty_struct *tty, int ldisc) { int retval; - struct tty_ldisc o_ldisc, new_ldisc; - int work; - unsigned long flags; + struct tty_ldisc *o_ldisc, *new_ldisc; + int work, o_work = 0; struct tty_struct *o_tty; -restart: - /* This is a bit ugly for now but means we can break the 'ldisc - is part of the tty struct' assumption later */ - retval = tty_ldisc_get(ldisc, &new_ldisc); - if (retval) - return retval; + new_ldisc = tty_ldisc_get(ldisc); + if (IS_ERR(new_ldisc)) + return PTR_ERR(new_ldisc); /* - * Problem: What do we do if this blocks ? + * We need to look at the tty locking here for pty/tty pairs + * when both sides try to change in parallel. */ - tty_wait_until_sent(tty, 0); + o_tty = tty->link; /* o_tty is the pty side or NULL */ + - if (tty->ldisc.ops->num == ldisc) { - tty_ldisc_put(new_ldisc.ops); + /* + * Check the no-op case + */ + + if (tty->ldisc->ops->num == ldisc) { + tty_ldisc_put(new_ldisc); return 0; } /* + * Problem: What do we do if this blocks ? + * We could deadlock here + */ + + tty_wait_until_sent(tty, 0); + + mutex_lock(&tty->ldisc_mutex); + + /* + * We could be midstream of another ldisc change which has + * dropped the lock during processing. If so we need to wait. + */ + + while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { + mutex_unlock(&tty->ldisc_mutex); + wait_event(tty_ldisc_wait, + test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); + mutex_lock(&tty->ldisc_mutex); + } + set_bit(TTY_LDISC_CHANGING, &tty->flags); + + /* * No more input please, we are switching. The new ldisc * will update this value in the ldisc open function */ @@ -533,8 +599,6 @@ restart: tty->receive_room = 0; o_ldisc = tty->ldisc; - o_tty = tty->link; - /* * Make sure we don't change while someone holds a * reference to the line discipline. The TTY_LDISC bit @@ -545,108 +609,181 @@ restart: * with a userspace app continually trying to use the tty in * parallel to the change and re-referencing the tty. */ - clear_bit(TTY_LDISC, &tty->flags); - if (o_tty) - clear_bit(TTY_LDISC, &o_tty->flags); - spin_lock_irqsave(&tty_ldisc_lock, flags); - if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) { - if (tty->ldisc.refcount) { - /* Free the new ldisc we grabbed. Must drop the lock - first. */ - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - tty_ldisc_put(o_ldisc.ops); - /* - * There are several reasons we may be busy, including - * random momentary I/O traffic. We must therefore - * retry. We could distinguish between blocking ops - * and retries if we made tty_ldisc_wait() smarter. - * That is up for discussion. - */ - if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0) - return -ERESTARTSYS; - goto restart; - } - if (o_tty && o_tty->ldisc.refcount) { - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - tty_ldisc_put(o_tty->ldisc.ops); - if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0) - return -ERESTARTSYS; - goto restart; - } - } - /* - * If the TTY_LDISC bit is set, then we are racing against - * another ldisc change - */ - if (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { - struct tty_ldisc *ld; - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - tty_ldisc_put(new_ldisc.ops); - ld = tty_ldisc_ref_wait(tty); - tty_ldisc_deref(ld); - goto restart; - } - /* - * This flag is used to avoid two parallel ldisc changes. Once - * open and close are fine grained locked this may work better - * as a mutex shared with the open/close/hup paths - */ - set_bit(TTY_LDISC_CHANGING, &tty->flags); + work = tty_ldisc_halt(tty); if (o_tty) - set_bit(TTY_LDISC_CHANGING, &o_tty->flags); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - - /* - * From this point on we know nobody has an ldisc - * usage reference, nor can they obtain one until - * we say so later on. - */ + o_work = tty_ldisc_halt(o_tty); - work = cancel_delayed_work(&tty->buf.work); /* - * Wait for ->hangup_work and ->buf.work handlers to terminate - * MUST NOT hold locks here. + * Wait for ->hangup_work and ->buf.work handlers to terminate. + * We must drop the mutex here in case a hangup is also in process. */ + + mutex_unlock(&tty->ldisc_mutex); + flush_scheduled_work(); + + /* Let any existing reference holders finish */ + retval = tty_ldisc_wait_idle(tty); + if (retval < 0) { + clear_bit(TTY_LDISC_CHANGING, &tty->flags); + tty_ldisc_put(new_ldisc); + return retval; + } + + mutex_lock(&tty->ldisc_mutex); + if (test_bit(TTY_HUPPED, &tty->flags)) { + /* We were raced by the hangup method. It will have stomped + the ldisc data and closed the ldisc down */ + clear_bit(TTY_LDISC_CHANGING, &tty->flags); + mutex_unlock(&tty->ldisc_mutex); + tty_ldisc_put(new_ldisc); + return -EIO; + } + /* Shutdown the current discipline. */ - if (o_ldisc.ops->close) - (o_ldisc.ops->close)(tty); + tty_ldisc_close(tty, o_ldisc); /* Now set up the new line discipline. */ - tty_ldisc_assign(tty, &new_ldisc); + tty_ldisc_assign(tty, new_ldisc); tty_set_termios_ldisc(tty, ldisc); - if (new_ldisc.ops->open) - retval = (new_ldisc.ops->open)(tty); + + retval = tty_ldisc_open(tty, new_ldisc); if (retval < 0) { - tty_ldisc_put(new_ldisc.ops); - tty_ldisc_restore(tty, &o_ldisc); + /* Back to the old one or N_TTY if we can't */ + tty_ldisc_put(new_ldisc); + tty_ldisc_restore(tty, o_ldisc); } + /* At this point we hold a reference to the new ldisc and a a reference to the old ldisc. If we ended up flipping back to the existing ldisc we have two references to it */ - if (tty->ldisc.ops->num != o_ldisc.ops->num && tty->ops->set_ldisc) + if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) tty->ops->set_ldisc(tty); - tty_ldisc_put(o_ldisc.ops); + tty_ldisc_put(o_ldisc); /* - * Allow ldisc referencing to occur as soon as the driver - * ldisc callback completes. + * Allow ldisc referencing to occur again */ tty_ldisc_enable(tty); if (o_tty) tty_ldisc_enable(o_tty); - /* Restart it in case no characters kick it off. Safe if + /* Restart the work queue in case no characters kick it off. Safe if already running */ if (work) schedule_delayed_work(&tty->buf.work, 1); + if (o_work) + schedule_delayed_work(&o_tty->buf.work, 1); + mutex_unlock(&tty->ldisc_mutex); return retval; } +/** + * tty_reset_termios - reset terminal state + * @tty: tty to reset + * + * Restore a terminal to the driver default state. + */ + +static void tty_reset_termios(struct tty_struct *tty) +{ + mutex_lock(&tty->termios_mutex); + *tty->termios = tty->driver->init_termios; + tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); + tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); + mutex_unlock(&tty->termios_mutex); +} + + +/** + * tty_ldisc_reinit - reinitialise the tty ldisc + * @tty: tty to reinit + * + * Switch the tty back to N_TTY line discipline and leave the + * ldisc state closed + */ + +static void tty_ldisc_reinit(struct tty_struct *tty) +{ + struct tty_ldisc *ld; + + tty_ldisc_close(tty, tty->ldisc); + tty_ldisc_put(tty->ldisc); + tty->ldisc = NULL; + /* + * Switch the line discipline back + */ + ld = tty_ldisc_get(N_TTY); + BUG_ON(IS_ERR(ld)); + tty_ldisc_assign(tty, ld); + tty_set_termios_ldisc(tty, N_TTY); +} + +/** + * tty_ldisc_hangup - hangup ldisc reset + * @tty: tty being hung up + * + * Some tty devices reset their termios when they receive a hangup + * event. In that situation we must also switch back to N_TTY properly + * before we reset the termios data. + * + * Locking: We can take the ldisc mutex as the rest of the code is + * careful to allow for this. + * + * In the pty pair case this occurs in the close() path of the + * tty itself so we must be careful about locking rules. + */ + +void tty_ldisc_hangup(struct tty_struct *tty) +{ + struct tty_ldisc *ld; + + /* + * FIXME! What are the locking issues here? This may me overdoing + * things... This question is especially important now that we've + * removed the irqlock. + */ + ld = tty_ldisc_ref(tty); + if (ld != NULL) { + /* We may have no line discipline at this point */ + if (ld->ops->flush_buffer) + ld->ops->flush_buffer(tty); + tty_driver_flush_buffer(tty); + if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && + ld->ops->write_wakeup) + ld->ops->write_wakeup(tty); + if (ld->ops->hangup) + ld->ops->hangup(tty); + tty_ldisc_deref(ld); + } + /* + * FIXME: Once we trust the LDISC code better we can wait here for + * ldisc completion and fix the driver call race + */ + wake_up_interruptible_poll(&tty->write_wait, POLLOUT); + wake_up_interruptible_poll(&tty->read_wait, POLLIN); + /* + * Shutdown the current line discipline, and reset it to + * N_TTY. + */ + if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) { + /* Avoid racing set_ldisc */ + mutex_lock(&tty->ldisc_mutex); + /* Switch back to N_TTY */ + tty_ldisc_reinit(tty); + /* At this point we have a closed ldisc and we want to + reopen it. We could defer this to the next open but + it means auditing a lot of other paths so this is a FIXME */ + WARN_ON(tty_ldisc_open(tty, tty->ldisc)); + tty_ldisc_enable(tty); + mutex_unlock(&tty->ldisc_mutex); + tty_reset_termios(tty); + } +} /** * tty_ldisc_setup - open line discipline @@ -654,24 +791,23 @@ restart: * @o_tty: pair tty for pty/tty pairs * * Called during the initial open of a tty/pty pair in order to set up the - * line discplines and bind them to the tty. + * line disciplines and bind them to the tty. This has no locking issues + * as the device isn't yet active. */ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) { - struct tty_ldisc *ld = &tty->ldisc; + struct tty_ldisc *ld = tty->ldisc; int retval; - if (ld->ops->open) { - retval = (ld->ops->open)(tty); - if (retval) - return retval; - } - if (o_tty && o_tty->ldisc.ops->open) { - retval = (o_tty->ldisc.ops->open)(o_tty); + retval = tty_ldisc_open(tty, ld); + if (retval) + return retval; + + if (o_tty) { + retval = tty_ldisc_open(o_tty, o_tty->ldisc); if (retval) { - if (ld->ops->close) - (ld->ops->close)(tty); + tty_ldisc_close(tty, ld); return retval; } tty_ldisc_enable(o_tty); @@ -679,34 +815,18 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) tty_ldisc_enable(tty); return 0; } - -static void tty_ldisc_reinit(struct tty_struct *tty) -{ - struct tty_ldisc ld; - - if (tty->ldisc.ops->close) - (tty->ldisc.ops->close)(tty); - tty_ldisc_put(tty->ldisc.ops); - /* - * Switch the line discipline back - */ - WARN_ON(tty_ldisc_get(N_TTY, &ld)); - tty_ldisc_assign(tty, &ld); - tty_set_termios_ldisc(tty, N_TTY); -} - /** * tty_ldisc_release - release line discipline * @tty: tty being shut down * @o_tty: pair tty for pty/tty pairs * * Called during the final close of a tty/pty pair in order to shut down the - * line discpline layer. + * line discpline layer. On exit the ldisc assigned is N_TTY and the + * ldisc has not been opened. */ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) { - /* * Prevent flush_to_ldisc() from rescheduling the work for later. Then * kill any delayed work. As this is the final close it does not @@ -714,6 +834,7 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) */ tty_ldisc_halt(tty); + flush_scheduled_work(); /* * Wait for any short term users (we know they are just driver @@ -730,11 +851,9 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) */ tty_ldisc_reinit(tty); - if (o_tty) { - /* FIXME: could o_tty be in setldisc here ? */ - clear_bit(TTY_LDISC, &o_tty->flags); - tty_ldisc_reinit(o_tty); - } + /* This will need doing differently if we need to lock */ + if (o_tty) + tty_ldisc_release(o_tty, NULL); } /** @@ -747,10 +866,10 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) void tty_ldisc_init(struct tty_struct *tty) { - struct tty_ldisc ld; - if (tty_ldisc_get(N_TTY, &ld) < 0) + struct tty_ldisc *ld = tty_ldisc_get(N_TTY); + if (IS_ERR(ld)) panic("n_tty: init_tty"); - tty_ldisc_assign(tty, &ld); + tty_ldisc_assign(tty, ld); } void tty_ldisc_begin(void) diff --git a/include/linux/tty.h b/include/linux/tty.h index f9c13c83790..1488d8c81aa 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -226,8 +226,11 @@ struct tty_struct { struct tty_driver *driver; const struct tty_operations *ops; int index; - /* The ldisc objects are protected by tty_ldisc_lock at the moment */ - struct tty_ldisc ldisc; + + /* Protects ldisc changes: Lock tty not pty */ + struct mutex ldisc_mutex; + struct tty_ldisc *ldisc; + struct mutex termios_mutex; spinlock_t ctrl_lock; /* Termios values are protected by the termios mutex */ @@ -314,6 +317,7 @@ struct tty_struct { #define TTY_CLOSING 7 /* ->close() in progress */ #define TTY_LDISC 9 /* Line discipline attached */ #define TTY_LDISC_CHANGING 10 /* Line discipline changing */ +#define TTY_LDISC_OPEN 11 /* Line discipline is open */ #define TTY_HW_COOK_OUT 14 /* Hardware can do output cooking */ #define TTY_HW_COOK_IN 15 /* Hardware can do input cooking */ #define TTY_PTY_LOCK 16 /* pty private */ @@ -406,6 +410,7 @@ extern int tty_termios_hw_change(struct ktermios *a, struct ktermios *b); extern struct tty_ldisc *tty_ldisc_ref(struct tty_struct *); extern void tty_ldisc_deref(struct tty_ldisc *); extern struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *); +extern void tty_ldisc_hangup(struct tty_struct *tty); extern const struct file_operations tty_ldiscs_proc_fops; extern void tty_wakeup(struct tty_struct *tty); |