diff options
| -rw-r--r-- | drivers/char/tty_ldisc.c | 152 | ||||
| -rw-r--r-- | include/linux/tty_ldisc.h | 2 |
2 files changed, 54 insertions, 100 deletions
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c index acd76b767d4..1733d3439ad 100644 --- a/drivers/char/tty_ldisc.c +++ b/drivers/char/tty_ldisc.c @@ -48,6 +48,41 @@ 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 @@ -142,7 +177,7 @@ static struct tty_ldisc *tty_ldisc_try_get(int disc) /* lock it */ ldops->refcount++; ld->ops = ldops; - ld->refcount = 0; + atomic_set(&ld->users, 1); err = 0; } } @@ -181,35 +216,6 @@ static struct tty_ldisc *tty_ldisc_get(int disc) return ld; } -/** - * tty_ldisc_put - drop ldisc reference - * @ld: ldisc - * - * Drop a reference to a line discipline. Manage refcounts and - * 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 *ld) -{ - unsigned long flags; - 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); - ldo = tty_ldiscs[disc]; - BUG_ON(ldo->refcount == 0); - ldo->refcount--; - module_put(ldo->owner); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - WARN_ON(ld->refcount); - kfree(ld); -} - static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) { return (*pos < NR_LDISCS) ? pos : NULL; @@ -234,7 +240,7 @@ static int tty_ldiscs_seq_show(struct seq_file *m, void *v) if (IS_ERR(ld)) return 0; seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i); - tty_ldisc_put(ld); + put_ldisc(ld); return 0; } @@ -288,20 +294,17 @@ 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; } /** @@ -322,10 +325,11 @@ 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); @@ -342,9 +346,7 @@ 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 NULL; + return tty_ldisc_try(tty); } EXPORT_SYMBOL_GPL(tty_ldisc_ref); @@ -360,21 +362,15 @@ 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 @@ -523,31 +519,6 @@ static int tty_ldisc_halt(struct tty_struct *tty) } /** - * 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. - * - * tty_ldisc_lock protects the ref counts currently. - */ - -static int tty_ldisc_wait_idle(struct tty_struct *tty) -{ - unsigned long flags; - spin_lock_irqsave(&tty_ldisc_lock, flags); - while (tty->ldisc->refcount) { - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - 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; -} - -/** * tty_set_ldisc - set line discipline * @tty: the terminal to set * @ldisc: the line discipline @@ -642,14 +613,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) 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 @@ -795,7 +758,6 @@ void tty_ldisc_hangup(struct tty_struct *tty) if (tty->ldisc) { /* Not yet closed */ /* Switch back to N_TTY */ tty_ldisc_halt(tty); - tty_ldisc_wait_idle(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 @@ -860,14 +822,6 @@ 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 - * side waiters as the file is closing so user count on the file - * side is zero. - */ - - tty_ldisc_wait_idle(tty); - mutex_lock(&tty->ldisc_mutex); /* * Now kill off the ldisc diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h index 40f38d89677..0c4ee9b88f8 100644 --- a/include/linux/tty_ldisc.h +++ b/include/linux/tty_ldisc.h @@ -144,7 +144,7 @@ struct tty_ldisc_ops { struct tty_ldisc { struct tty_ldisc_ops *ops; - int refcount; + atomic_t users; }; #define TTY_LDISC_MAGIC 0x5403 |