X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=drivers%2Fchar%2Ftty_ldisc.c;h=500e740ec5e469c63c5d873a59bb7bede1345986;hb=b66e65e2fea9392bdccc27b14b00c26b286eb248;hp=f78f5b0127a88501ec0b21cf9d42c517209ad933;hpb=e5824c97a993ac5bd22cec34e6cb6f85d39b73ba;p=safe%2Fjmp%2Flinux-2.6 diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c index f78f5b0..500e740 100644 --- a/drivers/char/tty_ldisc.c +++ b/drivers/char/tty_ldisc.c @@ -21,7 +21,6 @@ #include #include #include -#include #include #include #include @@ -35,6 +34,8 @@ #include #include +#include /* For the moment */ + #include #include @@ -49,6 +50,41 @@ static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); /* Line disc dispatch table */ static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; +static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld) +{ + if (ld) + atomic_inc(&ld->users); + return ld; +} + +static void put_ldisc(struct tty_ldisc *ld) +{ + unsigned long flags; + + if (WARN_ON_ONCE(!ld)) + return; + + /* + * If this is the last user, free the ldisc, and + * release the ldisc ops. + * + * We really want an "atomic_dec_and_lock_irqsave()", + * but we don't have it, so this does it by hand. + */ + local_irq_save(flags); + if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) { + struct tty_ldisc_ops *ldo = ld->ops; + + ldo->refcount--; + module_put(ldo->owner); + spin_unlock_irqrestore(&tty_ldisc_lock, flags); + + kfree(ld); + return; + } + local_irq_restore(flags); +} + /** * tty_register_ldisc - install a line discipline * @disc: ldisc number @@ -111,46 +147,38 @@ int tty_unregister_ldisc(int disc) } 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 - */ - -static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld) +static struct tty_ldisc_ops *get_ldops(int disc) { unsigned long flags; - struct tty_ldisc_ops *ldops; - int err = -EINVAL; - + struct tty_ldisc_ops *ldops, *ret; + spin_lock_irqsave(&tty_ldisc_lock, flags); - ld->ops = NULL; + ret = ERR_PTR(-EINVAL); ldops = tty_ldiscs[disc]; - /* Check the entry is defined */ if (ldops) { - /* If the module is being unloaded we can't use it */ - if (!try_module_get(ldops->owner)) - err = -EAGAIN; - else { - /* lock it */ + ret = ERR_PTR(-EAGAIN); + if (try_module_get(ldops->owner)) { ldops->refcount++; - ld->ops = ldops; - err = 0; + ret = ldops; } } spin_unlock_irqrestore(&tty_ldisc_lock, flags); - return err; + return ret; +} + +static void put_ldops(struct tty_ldisc_ops *ldops) +{ + unsigned long flags; + + spin_lock_irqsave(&tty_ldisc_lock, flags); + ldops->refcount--; + module_put(ldops->owner); + spin_unlock_irqrestore(&tty_ldisc_lock, flags); } /** * 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. @@ -161,52 +189,43 @@ 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; + struct tty_ldisc_ops *ldops; if (disc < N_TTY || disc >= NR_LDISCS) - return -EINVAL; - err = tty_ldisc_try_get(disc, ld); - if (err < 0) { + return ERR_PTR(-EINVAL); + + /* + * Get the ldisc ops - we may need to request them to be loaded + * dynamically and try again. + */ + ldops = get_ldops(disc); + if (IS_ERR(ldops)) { request_module("tty-ldisc-%d", disc); - err = tty_ldisc_try_get(disc, ld); + ldops = get_ldops(disc); + if (IS_ERR(ldops)) + return ERR_CAST(ldops); } - return err; -} - -/** - * tty_ldisc_put - drop ldisc reference - * @disc: ldisc number - * - * Drop a reference to a line discipline. Manage refcounts and - * module usage counts - * - * Locking: - * takes tty_ldisc_lock to guard against ldisc races - */ - -static void tty_ldisc_put(struct tty_ldisc_ops *ld) -{ - unsigned long flags; - int disc = ld->num; - BUG_ON(disc < N_TTY || disc >= NR_LDISCS); + ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); + if (ld == NULL) { + put_ldops(ldops); + return ERR_PTR(-ENOMEM); + } - spin_lock_irqsave(&tty_ldisc_lock, flags); - ld = tty_ldiscs[disc]; - BUG_ON(ld->refcount == 0); - ld->refcount--; - module_put(ld->owner); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); + ld->ops = ldops; + atomic_set(&ld->users, 1); + return ld; } -static void * tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) +static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) { return (*pos < NR_LDISCS) ? pos : NULL; } -static void * tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) +static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) { (*pos)++; return (*pos < NR_LDISCS) ? pos : NULL; @@ -219,12 +238,13 @@ 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; - - if (tty_ldisc_get(i, &ld) < 0) + struct tty_ldisc_ops *ldops; + + ldops = get_ldops(i); + if (IS_ERR(ldops)) 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", ldops->name ? ldops->name : "???", i); + put_ldops(ldops); return 0; } @@ -254,7 +274,7 @@ const struct file_operations tty_ldiscs_proc_fops = { * @ld: line discipline * * Install an instance of a line discipline into a tty structure. The - * ldisc must have a reference count above zero to ensure it remains/ + * ldisc must have a reference count above zero to ensure it remains. * The tty instance refcount starts at zero. * * Locking: @@ -263,8 +283,7 @@ 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; } /** @@ -279,20 +298,17 @@ static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) * Locking: takes tty_ldisc_lock */ -static int tty_ldisc_try(struct tty_struct *tty) +static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) { unsigned long flags; struct tty_ldisc *ld; - int ret = 0; spin_lock_irqsave(&tty_ldisc_lock, flags); - ld = &tty->ldisc; - if (test_bit(TTY_LDISC, &tty->flags)) { - ld->refcount++; - ret = 1; - } + ld = NULL; + if (test_bit(TTY_LDISC, &tty->flags)) + ld = get_ldisc(tty->ldisc); spin_unlock_irqrestore(&tty_ldisc_lock, flags); - return ret; + return ld; } /** @@ -313,12 +329,12 @@ static int tty_ldisc_try(struct tty_struct *tty) struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) { + struct tty_ldisc *ld; + /* wait_event is a macro */ - wait_event(tty_ldisc_wait, tty_ldisc_try(tty)); - WARN_ON(tty->ldisc.refcount == 0); - return &tty->ldisc; + wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); + return ld; } - EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); /** @@ -334,11 +350,8 @@ 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 NULL; + return tty_ldisc_try(tty); } - EXPORT_SYMBOL_GPL(tty_ldisc_ref); /** @@ -353,22 +366,15 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref); void tty_ldisc_deref(struct tty_ldisc *ld) { - unsigned long flags; - - BUG_ON(ld == NULL); - - spin_lock_irqsave(&tty_ldisc_lock, flags); - if (ld->refcount == 0) - printk(KERN_ERR "tty_ldisc_deref: no references.\n"); - else - ld->refcount--; - if (ld->refcount == 0) - wake_up(&tty_ldisc_wait); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); + put_ldisc(ld); } - EXPORT_SYMBOL_GPL(tty_ldisc_deref); +static inline void tty_ldisc_put(struct tty_ldisc *ld) +{ + put_ldisc(ld); +} + /** * tty_ldisc_enable - allow ldisc use * @tty: terminal to activate ldisc on @@ -389,6 +395,26 @@ void tty_ldisc_enable(struct tty_struct *tty) } /** + * tty_ldisc_flush - flush line discipline queue + * @tty: tty + * + * Flush the line discipline queue (if any) for this tty. If there + * is no line discipline active this is a no-op. + */ + +void tty_ldisc_flush(struct tty_struct *tty) +{ + struct tty_ldisc *ld = tty_ldisc_ref(tty); + if (ld) { + if (ld->ops->flush_buffer) + ld->ops->flush_buffer(tty); + tty_ldisc_deref(ld); + } + tty_buffer_flush(tty); +} +EXPORT_SYMBOL_GPL(tty_ldisc_flush); + +/** * tty_set_termios_ldisc - set ldisc field * @tty: tty structure * @num: line discipline number @@ -407,6 +433,45 @@ 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) { + int ret; + /* BKL here locks verus a hangup event */ + lock_kernel(); + ret = ld->ops->open(tty); + unlock_kernel(); + return ret; + } + 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 @@ -420,67 +485,119 @@ 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 - shut down the line discipline + * @tty: tty device + * + * Shut down the line discipline and work queue for this tty device. + * The TTY_LDISC flag being cleared ensures no further references can + * be obtained while the delayed work queue halt ensures that no more + * data is fed to the ldisc. + * + * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) + * in order to make sure any currently executing ldisc work is also + * flushed. + */ + +static int tty_ldisc_halt(struct tty_struct *tty) +{ + clear_bit(TTY_LDISC, &tty->flags); + return cancel_delayed_work_sync(&tty->buf.work); +} + +/** * tty_set_ldisc - set line discipline * @tty: the terminal to set * @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); + + lock_kernel(); + /* + * We need to look at the tty locking here for pty/tty pairs + * when both sides try to change in parallel. + */ + + o_tty = tty->link; /* o_tty is the pty side or NULL */ + /* + * Check the no-op case + */ + + if (tty->ldisc->ops->num == ldisc) { + unlock_kernel(); + tty_ldisc_put(new_ldisc); + return 0; + } + + unlock_kernel(); + /* * Problem: What do we do if this blocks ? + * We could deadlock here */ tty_wait_until_sent(tty, 0); - if (tty->ldisc.ops->num == ldisc) { - tty_ldisc_put(new_ldisc.ops); - return 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); } + lock_kernel(); + + 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 @@ -489,8 +606,8 @@ restart: tty->receive_room = 0; o_ldisc = tty->ldisc; - o_tty = tty->link; + unlock_kernel(); /* * Make sure we don't change while someone holds a * reference to the line discipline. The TTY_LDISC bit @@ -501,108 +618,190 @@ 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(); + + mutex_lock(&tty->ldisc_mutex); + lock_kernel(); + 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); + unlock_kernel(); + 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); + unlock_kernel(); 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 + * @ldisc: line discipline to reinitialize + * + * Switch the tty to a line discipline and leave the ldisc + * state closed + */ + +static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc) +{ + 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(ldisc); + BUG_ON(IS_ERR(ld)); + tty_ldisc_assign(tty, ld); + tty_set_termios_ldisc(tty, ldisc); +} + +/** + * 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; + int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; + int err = 0; + + /* + * 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 need be. + * + * Avoid racing set_ldisc or tty_ldisc_release + */ + mutex_lock(&tty->ldisc_mutex); + tty_ldisc_halt(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 */ + if (tty->ldisc) { /* Not yet closed */ + if (reset == 0) { + tty_ldisc_reinit(tty, tty->termios->c_line); + err = tty_ldisc_open(tty, tty->ldisc); + } + /* If the re-open fails or we reset then go to N_TTY. The + N_TTY open cannot fail */ + if (reset || err) { + tty_ldisc_reinit(tty, N_TTY); + WARN_ON(tty_ldisc_open(tty, tty->ldisc)); + } + tty_ldisc_enable(tty); + } + mutex_unlock(&tty->ldisc_mutex); + if (reset) + tty_reset_termios(tty); +} /** * tty_ldisc_setup - open line discipline @@ -610,24 +809,23 @@ 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); @@ -635,71 +833,46 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) tty_ldisc_enable(tty); return 0; } - /** * 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. + * Called during the final close of a tty/pty pair in order to shut down + * the 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) { - unsigned long flags; - struct tty_ldisc ld; /* * Prevent flush_to_ldisc() from rescheduling the work for later. Then * kill any delayed work. As this is the final close it does not * race with the set_ldisc code path. */ - clear_bit(TTY_LDISC, &tty->flags); - cancel_delayed_work(&tty->buf.work); - - /* - * Wait for ->hangup_work and ->buf.work handlers to terminate - */ + tty_ldisc_halt(tty); flush_scheduled_work(); + mutex_lock(&tty->ldisc_mutex); /* - * Wait for any short term users (we know they are just driver - * side waiters as the file is closing so user count on the file - * side is zero. - */ - spin_lock_irqsave(&tty_ldisc_lock, flags); - while (tty->ldisc.refcount) { - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0); - spin_lock_irqsave(&tty_ldisc_lock, flags); - } - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - /* - * Shutdown the current line discipline, and reset it to N_TTY. - * - * FIXME: this MUST get fixed for the new reflocking + * Now kill off the ldisc */ - if (tty->ldisc.ops->close) - (tty->ldisc.ops->close)(tty); - tty_ldisc_put(tty->ldisc.ops); + tty_ldisc_close(tty, tty->ldisc); + tty_ldisc_put(tty->ldisc); + /* Force an oops if we mess this up */ + tty->ldisc = NULL; - /* - * Switch the line discipline back - */ - WARN_ON(tty_ldisc_get(N_TTY, &ld)); - tty_ldisc_assign(tty, &ld); + /* Ensure the next open requests the N_TTY ldisc */ tty_set_termios_ldisc(tty, N_TTY); - if (o_tty) { - /* FIXME: could o_tty be in setldisc here ? */ - clear_bit(TTY_LDISC, &o_tty->flags); - if (o_tty->ldisc.ops->close) - (o_tty->ldisc.ops->close)(o_tty); - tty_ldisc_put(o_tty->ldisc.ops); - WARN_ON(tty_ldisc_get(N_TTY, &ld)); - tty_ldisc_assign(o_tty, &ld); - tty_set_termios_ldisc(o_tty, N_TTY); - } + mutex_unlock(&tty->ldisc_mutex); + + /* This will need doing differently if we need to lock */ + if (o_tty) + tty_ldisc_release(o_tty, NULL); + + /* And the memory resources remaining (buffers, termios) will be + disposed of when the kref hits zero */ } /** @@ -712,10 +885,10 @@ 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)