diff options
Diffstat (limited to 'drivers/tty/tty_ldisc.c')
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 609 |
1 files changed, 242 insertions, 367 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 4214d58276f..2d822aa259b 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -1,43 +1,41 @@ #include <linux/types.h> -#include <linux/major.h> #include <linux/errno.h> -#include <linux/signal.h> -#include <linux/fcntl.h> +#include <linux/kmod.h> #include <linux/sched.h> #include <linux/interrupt.h> #include <linux/tty.h> #include <linux/tty_driver.h> -#include <linux/tty_flip.h> -#include <linux/devpts_fs.h> #include <linux/file.h> -#include <linux/console.h> -#include <linux/timer.h> -#include <linux/ctype.h> -#include <linux/kd.h> #include <linux/mm.h> #include <linux/string.h> #include <linux/slab.h> #include <linux/poll.h> #include <linux/proc_fs.h> -#include <linux/init.h> #include <linux/module.h> #include <linux/device.h> #include <linux/wait.h> #include <linux/bitops.h> -#include <linux/delay.h> #include <linux/seq_file.h> - #include <linux/uaccess.h> -#include <asm/system.h> - -#include <linux/kbd_kern.h> -#include <linux/vt_kern.h> -#include <linux/selection.h> - -#include <linux/smp_lock.h> /* For the moment */ +#include <linux/ratelimit.h> + +#undef LDISC_DEBUG_HANGUP + +#ifdef LDISC_DEBUG_HANGUP +#define tty_ldisc_debug(tty, f, args...) ({ \ + char __b[64]; \ + printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \ +}) +#else +#define tty_ldisc_debug(tty, f, args...) +#endif + +/* lockdep nested classes for tty->ldisc_sem */ +enum { + LDISC_SEM_NORMAL, + LDISC_SEM_OTHER, +}; -#include <linux/kmod.h> -#include <linux/nsproxy.h> /* * This guards the refcounted line discipline lists. The lock @@ -45,48 +43,10 @@ * callers who will do ldisc lookups and cannot sleep. */ -static DEFINE_SPINLOCK(tty_ldisc_lock); -static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); -static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle); +static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); /* 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); - wake_up(&tty_ldisc_idle); -} - /** * tty_register_ldisc - install a line discipline * @disc: ldisc number @@ -97,7 +57,7 @@ static void put_ldisc(struct tty_ldisc *ld) * from this point onwards. * * Locking: - * takes tty_ldisc_lock to guard against ldisc races + * takes tty_ldiscs_lock to guard against ldisc races */ int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) @@ -108,11 +68,11 @@ int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) if (disc < N_TTY || disc >= NR_LDISCS) return -EINVAL; - spin_lock_irqsave(&tty_ldisc_lock, flags); + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); tty_ldiscs[disc] = new_ldisc; new_ldisc->num = disc; new_ldisc->refcount = 0; - spin_unlock_irqrestore(&tty_ldisc_lock, flags); + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); return ret; } @@ -127,7 +87,7 @@ EXPORT_SYMBOL(tty_register_ldisc); * currently in use. * * Locking: - * takes tty_ldisc_lock to guard against ldisc races + * takes tty_ldiscs_lock to guard against ldisc races */ int tty_unregister_ldisc(int disc) @@ -138,12 +98,12 @@ int tty_unregister_ldisc(int disc) if (disc < N_TTY || disc >= NR_LDISCS) return -EINVAL; - spin_lock_irqsave(&tty_ldisc_lock, flags); + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); if (tty_ldiscs[disc]->refcount) ret = -EBUSY; else tty_ldiscs[disc] = NULL; - spin_unlock_irqrestore(&tty_ldisc_lock, flags); + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); return ret; } @@ -154,7 +114,7 @@ static struct tty_ldisc_ops *get_ldops(int disc) unsigned long flags; struct tty_ldisc_ops *ldops, *ret; - spin_lock_irqsave(&tty_ldisc_lock, flags); + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); ret = ERR_PTR(-EINVAL); ldops = tty_ldiscs[disc]; if (ldops) { @@ -164,7 +124,7 @@ static struct tty_ldisc_ops *get_ldops(int disc) ret = ldops; } } - spin_unlock_irqrestore(&tty_ldisc_lock, flags); + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); return ret; } @@ -172,10 +132,10 @@ static void put_ldops(struct tty_ldisc_ops *ldops) { unsigned long flags; - spin_lock_irqsave(&tty_ldisc_lock, flags); + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); ldops->refcount--; module_put(ldops->owner); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); } /** @@ -188,10 +148,10 @@ static void put_ldops(struct tty_ldisc_ops *ldops) * available * * Locking: - * takes tty_ldisc_lock to guard against ldisc races + * takes tty_ldiscs_lock to guard against ldisc races */ -static struct tty_ldisc *tty_ldisc_get(int disc) +static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) { struct tty_ldisc *ld; struct tty_ldisc_ops *ldops; @@ -218,10 +178,25 @@ static struct tty_ldisc *tty_ldisc_get(int disc) } ld->ops = ldops; - atomic_set(&ld->users, 1); + ld->tty = tty; + return ld; } +/** + * tty_ldisc_put - release the ldisc + * + * Complement of tty_ldisc_get(). + */ +static inline void tty_ldisc_put(struct tty_ldisc *ld) +{ + if (WARN_ON_ONCE(!ld)) + return; + + put_ldops(ld->ops); + kfree(ld); +} + static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) { return (*pos < NR_LDISCS) ? pos : NULL; @@ -271,49 +246,6 @@ const struct file_operations tty_ldiscs_proc_fops = { }; /** - * tty_ldisc_assign - set ldisc on a tty - * @tty: tty to assign - * @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. - * The tty instance refcount starts at zero. - * - * Locking: - * Caller must hold references - */ - -static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) -{ - tty->ldisc = ld; -} - -/** - * tty_ldisc_try - internal helper - * @tty: the tty - * - * Make a single attempt to grab and bump the refcount on - * the tty ldisc. Return 0 on failure or 1 on success. This is - * used to implement both the waiting and non waiting versions - * of tty_ldisc_ref - * - * Locking: takes tty_ldisc_lock - */ - -static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) -{ - unsigned long flags; - struct tty_ldisc *ld; - - spin_lock_irqsave(&tty_ldisc_lock, flags); - ld = NULL; - if (test_bit(TTY_LDISC, &tty->flags)) - ld = get_ldisc(tty->ldisc); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - return ld; -} - -/** * tty_ldisc_ref_wait - wait for the tty ldisc * @tty: tty device * @@ -326,16 +258,15 @@ static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) * against a discipline change, such as an existing ldisc reference * (which we check for) * - * Locking: call functions take tty_ldisc_lock + * Note: only callable from a file_operations routine (which + * guarantees tty->ldisc != NULL when the lock is acquired). */ 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, (ld = tty_ldisc_try(tty)) != NULL); - return ld; + ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); + WARN_ON(!tty->ldisc); + return tty->ldisc; } EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); @@ -346,13 +277,18 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); * Dereference the line discipline for the terminal and take a * reference to it. If the line discipline is in flux then * return NULL. Can be called from IRQ and timer functions. - * - * Locking: called functions take tty_ldisc_lock */ struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) { - return tty_ldisc_try(tty); + struct tty_ldisc *ld = NULL; + + if (ldsem_down_read_trylock(&tty->ldisc_sem)) { + ld = tty->ldisc; + if (!ld) + ldsem_up_read(&tty->ldisc_sem); + } + return ld; } EXPORT_SYMBOL_GPL(tty_ldisc_ref); @@ -362,38 +298,91 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref); * * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May * be called in IRQ context. - * - * Locking: takes tty_ldisc_lock */ void tty_ldisc_deref(struct tty_ldisc *ld) { - put_ldisc(ld); + ldsem_up_read(&ld->tty->ldisc_sem); } EXPORT_SYMBOL_GPL(tty_ldisc_deref); -static inline void tty_ldisc_put(struct tty_ldisc *ld) + +static inline int __lockfunc +tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) { - put_ldisc(ld); + return ldsem_down_write(&tty->ldisc_sem, timeout); } -/** - * tty_ldisc_enable - allow ldisc use - * @tty: terminal to activate ldisc on - * - * Set the TTY_LDISC flag when the line discipline can be called - * again. Do necessary wakeups for existing sleepers. Clear the LDISC - * changing flag to indicate any ldisc change is now over. - * - * Note: nobody should set the TTY_LDISC bit except via this function. - * Clearing directly is allowed. - */ +static inline int __lockfunc +tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) +{ + return ldsem_down_write_nested(&tty->ldisc_sem, + LDISC_SEM_OTHER, timeout); +} + +static inline void tty_ldisc_unlock(struct tty_struct *tty) +{ + return ldsem_up_write(&tty->ldisc_sem); +} + +static int __lockfunc +tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, + unsigned long timeout) +{ + int ret; + + if (tty < tty2) { + ret = tty_ldisc_lock(tty, timeout); + if (ret) { + ret = tty_ldisc_lock_nested(tty2, timeout); + if (!ret) + tty_ldisc_unlock(tty); + } + } else { + /* if this is possible, it has lots of implications */ + WARN_ON_ONCE(tty == tty2); + if (tty2 && tty != tty2) { + ret = tty_ldisc_lock(tty2, timeout); + if (ret) { + ret = tty_ldisc_lock_nested(tty, timeout); + if (!ret) + tty_ldisc_unlock(tty2); + } + } else + ret = tty_ldisc_lock(tty, timeout); + } + + if (!ret) + return -EBUSY; + + set_bit(TTY_LDISC_HALTED, &tty->flags); + if (tty2) + set_bit(TTY_LDISC_HALTED, &tty2->flags); + return 0; +} + +static void __lockfunc +tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) +{ + tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); +} + +static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty, + struct tty_struct *tty2) +{ + tty_ldisc_unlock(tty); + if (tty2) + tty_ldisc_unlock(tty2); +} -void tty_ldisc_enable(struct tty_struct *tty) +static void __lockfunc tty_ldisc_enable_pair(struct tty_struct *tty, + struct tty_struct *tty2) { - set_bit(TTY_LDISC, &tty->flags); - clear_bit(TTY_LDISC_CHANGING, &tty->flags); - wake_up(&tty_ldisc_wait); + clear_bit(TTY_LDISC_HALTED, &tty->flags); + if (tty2) + clear_bit(TTY_LDISC_HALTED, &tty2->flags); + + tty_ldisc_unlock_pair(tty, tty2); } /** @@ -425,14 +414,14 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush); * they are not on hot paths so a little discipline won't do * any harm. * - * Locking: takes termios_mutex + * Locking: takes termios_rwsem */ static void tty_set_termios_ldisc(struct tty_struct *tty, int num) { - mutex_lock(&tty->termios_mutex); - tty->termios->c_line = num; - mutex_unlock(&tty->termios_mutex); + down_write(&tty->termios_rwsem); + tty->termios.c_line = num; + up_write(&tty->termios_rwsem); } /** @@ -452,7 +441,6 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) if (ld->ops->open) { int ret; /* BTM here locks versus a hangup event */ - WARN_ON(!tty_locked()); ret = ld->ops->open(tty); if (ret) clear_bit(TTY_LDISC_OPEN, &tty->flags); @@ -494,17 +482,17 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) int r; /* There is an outstanding reference here so this is safe */ - old = tty_ldisc_get(old->ops->num); + old = tty_ldisc_get(tty, old->ops->num); WARN_ON(IS_ERR(old)); - tty_ldisc_assign(tty, old); + tty->ldisc = old; tty_set_termios_ldisc(tty, old->ops->num); if (tty_ldisc_open(tty, old) < 0) { tty_ldisc_put(old); /* This driver is always present */ - new_ldisc = tty_ldisc_get(N_TTY); + new_ldisc = tty_ldisc_get(tty, N_TTY); if (IS_ERR(new_ldisc)) panic("n_tty: get"); - tty_ldisc_assign(tty, new_ldisc); + tty->ldisc = new_ldisc; tty_set_termios_ldisc(tty, N_TTY); r = tty_ldisc_open(tty, new_ldisc); if (r < 0) @@ -515,43 +503,6 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) } /** - * 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_ldisc_wait_idle - wait for the ldisc to become idle - * @tty: tty to wait for - * - * Wait for the line discipline to become idle. The discipline must - * have been halted for this to guarantee it remains idle. - */ -static int tty_ldisc_wait_idle(struct tty_struct *tty) -{ - int ret; - ret = wait_event_interruptible_timeout(tty_ldisc_idle, - atomic_read(&tty->ldisc->users) == 1, 5 * HZ); - if (ret < 0) - return ret; - return ret > 0 ? 0 : -EBUSY; -} - -/** * tty_set_ldisc - set line discipline * @tty: the terminal to set * @ldisc: the line discipline @@ -560,162 +511,84 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty) * 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, termios_mutex */ int tty_set_ldisc(struct tty_struct *tty, int ldisc) { int retval; - struct tty_ldisc *o_ldisc, *new_ldisc; - int work, o_work = 0; - struct tty_struct *o_tty; + struct tty_ldisc *old_ldisc, *new_ldisc; + struct tty_struct *o_tty = tty->link; - new_ldisc = tty_ldisc_get(ldisc); + new_ldisc = tty_ldisc_get(tty, ldisc); if (IS_ERR(new_ldisc)) return PTR_ERR(new_ldisc); - tty_lock(); - /* - * 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 */ - + retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ); + if (retval) { + tty_ldisc_put(new_ldisc); + return retval; + } /* * Check the no-op case */ if (tty->ldisc->ops->num == ldisc) { - tty_unlock(); + tty_ldisc_enable_pair(tty, o_tty); tty_ldisc_put(new_ldisc); return 0; } - tty_unlock(); - /* - * Problem: What do we do if this blocks ? - * We could deadlock here - */ - - tty_wait_until_sent(tty, 0); - - tty_lock(); - 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); - tty_unlock(); - wait_event(tty_ldisc_wait, - test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); - tty_lock(); - 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 - */ - - tty->receive_room = 0; - - o_ldisc = tty->ldisc; - - tty_unlock(); - /* - * Make sure we don't change while someone holds a - * reference to the line discipline. The TTY_LDISC bit - * prevents anyone taking a reference once it is clear. - * We need the lock to avoid racing reference takers. - * - * We must clear the TTY_LDISC bit here to avoid a livelock - * with a userspace app continually trying to use the tty in - * parallel to the change and re-referencing the tty. - */ - - work = tty_ldisc_halt(tty); - if (o_tty) - o_work = tty_ldisc_halt(o_tty); - - /* - * Wait for ->hangup_work and ->buf.work handlers to terminate. - * We must drop the mutex here in case a hangup is also in process. - */ + old_ldisc = tty->ldisc; + tty_lock(tty); - mutex_unlock(&tty->ldisc_mutex); - - flush_scheduled_work(); - - retval = tty_ldisc_wait_idle(tty); - - tty_lock(); - mutex_lock(&tty->ldisc_mutex); - - /* handle wait idle failure locked */ - if (retval) { - tty_ldisc_put(new_ldisc); - goto enable; - } - - if (test_bit(TTY_HUPPED, &tty->flags)) { + if (test_bit(TTY_HUPPING, &tty->flags) || + 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_enable_pair(tty, o_tty); tty_ldisc_put(new_ldisc); - tty_unlock(); + tty_unlock(tty); return -EIO; } - /* Shutdown the current discipline. */ - tty_ldisc_close(tty, o_ldisc); + /* Shutdown the old discipline. */ + tty_ldisc_close(tty, old_ldisc); /* Now set up the new line discipline. */ - tty_ldisc_assign(tty, new_ldisc); + tty->ldisc = new_ldisc; tty_set_termios_ldisc(tty, ldisc); retval = tty_ldisc_open(tty, new_ldisc); if (retval < 0) { /* Back to the old one or N_TTY if we can't */ tty_ldisc_put(new_ldisc); - tty_ldisc_restore(tty, o_ldisc); + tty_ldisc_restore(tty, old_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 != old_ldisc->ops->num && tty->ops->set_ldisc) tty->ops->set_ldisc(tty); - tty_ldisc_put(o_ldisc); + /* At this point we hold a reference to the new ldisc and a + reference to the old ldisc, or we hold two references to + the old ldisc (if it was restored as part of error cleanup + above). In either case, releasing a single reference from + the old ldisc is correct. */ + + tty_ldisc_put(old_ldisc); -enable: /* * Allow ldisc referencing to occur again */ - - tty_ldisc_enable(tty); - if (o_tty) - tty_ldisc_enable(o_tty); + tty_ldisc_enable_pair(tty, o_tty); /* 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); - tty_unlock(); + schedule_work(&tty->port->buf.work); + if (o_tty) + schedule_work(&o_tty->port->buf.work); + + tty_unlock(tty); return retval; } @@ -728,11 +601,11 @@ enable: 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); + down_write(&tty->termios_rwsem); + 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); + up_write(&tty->termios_rwsem); } @@ -747,18 +620,17 @@ static void tty_reset_termios(struct tty_struct *tty) static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) { - struct tty_ldisc *ld = tty_ldisc_get(ldisc); + struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); if (IS_ERR(ld)) return -1; tty_ldisc_close(tty, tty->ldisc); tty_ldisc_put(tty->ldisc); - tty->ldisc = NULL; /* * Switch the line discipline back */ - tty_ldisc_assign(tty, ld); + tty->ldisc = ld; tty_set_termios_ldisc(tty, ldisc); return 0; @@ -785,14 +657,10 @@ void tty_ldisc_hangup(struct tty_struct *tty) 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. - */ + tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); + 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); @@ -803,41 +671,30 @@ void tty_ldisc_hangup(struct tty_struct *tty) 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); + + tty_unlock(tty); + /* * 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_lock_pair(tty, tty->link); + tty_lock(tty); - /* - * this is like tty_ldisc_halt, but we need to give up - * the BTM before calling cancel_delayed_work_sync, - * which may need to wait for another function taking the BTM - */ - clear_bit(TTY_LDISC, &tty->flags); - tty_unlock(); - cancel_delayed_work_sync(&tty->buf.work); - mutex_unlock(&tty->ldisc_mutex); - - tty_lock(); - mutex_lock(&tty->ldisc_mutex); - - /* 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 (tty->ldisc) { + + /* At this point we have a halted ldisc; we want to close it and + reopen a new ldisc. We could defer the reopen to the next + open but it means auditing a lot of other paths so this is + a FIXME */ if (reset == 0) { - if (!tty_ldisc_reinit(tty, tty->termios->c_line)) + if (!tty_ldisc_reinit(tty, tty->termios.c_line)) err = tty_ldisc_open(tty, tty->ldisc); else err = 1; @@ -848,11 +705,12 @@ void tty_ldisc_hangup(struct tty_struct *tty) BUG_ON(tty_ldisc_reinit(tty, N_TTY)); WARN_ON(tty_ldisc_open(tty, tty->ldisc)); } - tty_ldisc_enable(tty); } - mutex_unlock(&tty->ldisc_mutex); + tty_ldisc_enable_pair(tty, tty->link); if (reset) tty_reset_termios(tty); + + tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc); } /** @@ -880,11 +738,24 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) tty_ldisc_close(tty, ld); return retval; } - tty_ldisc_enable(o_tty); } - tty_ldisc_enable(tty); return 0; } + +static void tty_ldisc_kill(struct tty_struct *tty) +{ + /* + * Now kill off the ldisc + */ + tty_ldisc_close(tty, tty->ldisc); + tty_ldisc_put(tty->ldisc); + /* Force an oops if we mess this up */ + tty->ldisc = NULL; + + /* Ensure the next open requests the N_TTY ldisc */ + tty_set_termios_ldisc(tty, N_TTY); +} + /** * tty_ldisc_release - release line discipline * @tty: tty being shut down @@ -898,35 +769,26 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) 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 - * race with the set_ldisc code path. + * Shutdown this line discipline. As this is the final close, + * it does not race with the set_ldisc code path. */ - tty_unlock(); - tty_ldisc_halt(tty); - flush_scheduled_work(); - tty_lock(); - - mutex_lock(&tty->ldisc_mutex); - /* - * Now kill off the ldisc - */ - tty_ldisc_close(tty, tty->ldisc); - tty_ldisc_put(tty->ldisc); - /* Force an oops if we mess this up */ - tty->ldisc = NULL; + tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); - /* Ensure the next open requests the N_TTY ldisc */ - tty_set_termios_ldisc(tty, N_TTY); - mutex_unlock(&tty->ldisc_mutex); + tty_ldisc_lock_pair(tty, o_tty); + tty_lock_pair(tty, o_tty); - /* This will need doing differently if we need to lock */ + tty_ldisc_kill(tty); if (o_tty) - tty_ldisc_release(o_tty, NULL); + tty_ldisc_kill(o_tty); + + tty_unlock_pair(tty, o_tty); + tty_ldisc_unlock_pair(tty, o_tty); /* And the memory resources remaining (buffers, termios) will be disposed of when the kref hits zero */ + + tty_ldisc_debug(tty, "ldisc closed\n"); } /** @@ -939,10 +801,23 @@ 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 = tty_ldisc_get(N_TTY); + struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); if (IS_ERR(ld)) panic("n_tty: init_tty"); - tty_ldisc_assign(tty, ld); + tty->ldisc = ld; +} + +/** + * tty_ldisc_init - ldisc cleanup for new tty + * @tty: tty that was allocated recently + * + * The tty structure must not becompletely set up (tty_ldisc_setup) when + * this call is made. + */ +void tty_ldisc_deinit(struct tty_struct *tty) +{ + tty_ldisc_put(tty->ldisc); + tty->ldisc = NULL; } void tty_ldisc_begin(void) |