diff options
Diffstat (limited to 'drivers/tty/tty_ldisc.c')
-rw-r--r-- | drivers/tty/tty_ldisc.c | 198 |
1 files changed, 104 insertions, 94 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index a054d03..68947f6 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -140,9 +140,16 @@ static void put_ldops(struct tty_ldisc_ops *ldops) * @disc: ldisc number * * Takes a reference to a line discipline. Deals with refcounts and - * module locking counts. Returns NULL if the discipline is not available. - * Returns a pointer to the discipline and bumps the ref count if it is - * available + * module locking counts. + * + * Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or + * if the discipline is not registered + * -EAGAIN if request_module() failed to load or register the + * the discipline + * -ENOMEM if allocation failure + * + * Otherwise, returns a pointer to the discipline and bumps the + * ref count * * Locking: * takes tty_ldiscs_lock to guard against ldisc races @@ -250,19 +257,23 @@ const struct file_operations tty_ldiscs_proc_fops = { * reference to it. If the line discipline is in flux then * wait patiently until it changes. * + * Returns: NULL if the tty has been hungup and not re-opened with + * a new file descriptor, otherwise valid ldisc reference + * * Note: Must not be called from an IRQ/timer context. The caller * must also be careful not to hold other locks that will deadlock * against a discipline change, such as an existing ldisc reference * (which we check for) * - * Note: only callable from a file_operations routine (which - * guarantees tty->ldisc != NULL when the lock is acquired). + * Note: a file_operations routine (read/poll/write) should use this + * function to wait for any ldisc lifetime events to finish. */ struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) { ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); - WARN_ON(!tty->ldisc); + if (!tty->ldisc) + ldsem_up_read(&tty->ldisc_sem); return tty->ldisc; } EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); @@ -304,13 +315,13 @@ void tty_ldisc_deref(struct tty_ldisc *ld) EXPORT_SYMBOL_GPL(tty_ldisc_deref); -static inline int __lockfunc +static inline int __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) { return ldsem_down_write(&tty->ldisc_sem, timeout); } -static inline int __lockfunc +static inline int __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) { return ldsem_down_write_nested(&tty->ldisc_sem, @@ -322,8 +333,7 @@ static inline void __tty_ldisc_unlock(struct tty_struct *tty) ldsem_up_write(&tty->ldisc_sem); } -static int __lockfunc -tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) +static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) { int ret; @@ -340,7 +350,7 @@ static void tty_ldisc_unlock(struct tty_struct *tty) __tty_ldisc_unlock(tty); } -static int __lockfunc +static int tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, unsigned long timeout) { @@ -376,14 +386,13 @@ tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, return 0; } -static void __lockfunc -tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) +static void 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) +static void tty_ldisc_unlock_pair(struct tty_struct *tty, + struct tty_struct *tty2) { __tty_ldisc_unlock(tty); if (tty2) @@ -411,7 +420,7 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush); /** * tty_set_termios_ldisc - set ldisc field * @tty: tty structure - * @num: line discipline number + * @disc: line discipline number * * This is probably overkill for real world processors but * they are not on hot paths so a little discipline won't do @@ -424,10 +433,10 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush); * Locking: takes termios_rwsem */ -static void tty_set_termios_ldisc(struct tty_struct *tty, int num) +static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) { down_write(&tty->termios_rwsem); - tty->termios.c_line = num; + tty->termios.c_line = disc; up_write(&tty->termios_rwsem); tty->disc_data = NULL; @@ -455,7 +464,7 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) if (ret) clear_bit(TTY_LDISC_OPEN, &tty->flags); - tty_ldisc_debug(tty, "%p: opened\n", tty->ldisc); + tty_ldisc_debug(tty, "%p: opened\n", ld); return ret; } return 0; @@ -476,7 +485,7 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) clear_bit(TTY_LDISC_OPEN, &tty->flags); if (ld->ops->close) ld->ops->close(tty); - tty_ldisc_debug(tty, "%p: closed\n", tty->ldisc); + tty_ldisc_debug(tty, "%p: closed\n", ld); } /** @@ -525,12 +534,12 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) * the close of one side of a tty/pty pair, and eventually hangup. */ -int tty_set_ldisc(struct tty_struct *tty, int ldisc) +int tty_set_ldisc(struct tty_struct *tty, int disc) { int retval; struct tty_ldisc *old_ldisc, *new_ldisc; - new_ldisc = tty_ldisc_get(tty, ldisc); + new_ldisc = tty_ldisc_get(tty, disc); if (IS_ERR(new_ldisc)) return PTR_ERR(new_ldisc); @@ -539,8 +548,13 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) if (retval) goto err; + if (!tty->ldisc) { + retval = -EIO; + goto out; + } + /* Check the no-op case */ - if (tty->ldisc->ops->num == ldisc) + if (tty->ldisc->ops->num == disc) goto out; if (test_bit(TTY_HUPPED, &tty->flags)) { @@ -556,7 +570,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) /* Now set up the new line discipline. */ tty->ldisc = new_ldisc; - tty_set_termios_ldisc(tty, ldisc); + tty_set_termios_ldisc(tty, disc); retval = tty_ldisc_open(tty, new_ldisc); if (retval < 0) { @@ -590,6 +604,25 @@ err: } /** + * tty_ldisc_kill - teardown ldisc + * @tty: tty being released + * + * Perform final close of the ldisc and reset tty->ldisc + */ +static void tty_ldisc_kill(struct tty_struct *tty) +{ + if (!tty->ldisc) + return; + /* + * 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_reset_termios - reset terminal state * @tty: tty to reset * @@ -609,28 +642,44 @@ static void tty_reset_termios(struct tty_struct *tty) /** * tty_ldisc_reinit - reinitialise the tty ldisc * @tty: tty to reinit - * @ldisc: line discipline to reinitialize + * @disc: line discipline to reinitialize + * + * Completely reinitialize the line discipline state, by closing the + * current instance, if there is one, and opening a new instance. If + * an error occurs opening the new non-N_TTY instance, the instance + * is dropped and tty->ldisc reset to NULL. The caller can then retry + * with N_TTY instead. * - * Switch the tty to a line discipline and leave the ldisc - * state closed + * Returns 0 if successful, otherwise error code < 0 */ -static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) +int tty_ldisc_reinit(struct tty_struct *tty, int disc) { - struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); + struct tty_ldisc *ld; + int retval; - if (IS_ERR(ld)) - return -1; + ld = tty_ldisc_get(tty, disc); + if (IS_ERR(ld)) { + BUG_ON(disc == N_TTY); + return PTR_ERR(ld); + } - tty_ldisc_close(tty, tty->ldisc); - tty_ldisc_put(tty->ldisc); - /* - * Switch the line discipline back - */ - tty->ldisc = ld; - tty_set_termios_ldisc(tty, ldisc); + if (tty->ldisc) { + tty_ldisc_close(tty, tty->ldisc); + tty_ldisc_put(tty->ldisc); + } - return 0; + /* switch the line discipline */ + tty->ldisc = ld; + tty_set_termios_ldisc(tty, disc); + retval = tty_ldisc_open(tty, tty->ldisc); + if (retval) { + if (!WARN_ON(disc == N_TTY)) { + tty_ldisc_put(tty->ldisc); + tty->ldisc = NULL; + } + } + return retval; } /** @@ -648,13 +697,11 @@ static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) * tty itself so we must be careful about locking rules. */ -void tty_ldisc_hangup(struct tty_struct *tty) +void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) { struct tty_ldisc *ld; - int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; - int err = 0; - tty_ldisc_debug(tty, "%p: closing\n", tty->ldisc); + tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); ld = tty_ldisc_ref(tty); if (ld != NULL) { @@ -680,31 +727,17 @@ void tty_ldisc_hangup(struct tty_struct *tty) */ tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); - 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->driver->flags & TTY_DRIVER_RESET_TERMIOS) + tty_reset_termios(tty); - if (!tty_ldisc_reinit(tty, tty->termios.c_line)) - err = tty_ldisc_open(tty, tty->ldisc); - else - err = 1; - } - /* If the re-open fails or we reset then go to N_TTY. The - N_TTY open cannot fail */ - if (reset || err) { - BUG_ON(tty_ldisc_reinit(tty, N_TTY)); - WARN_ON(tty_ldisc_open(tty, tty->ldisc)); - } + if (tty->ldisc) { + if (reinit) { + if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0) + tty_ldisc_reinit(tty, N_TTY); + } else + tty_ldisc_kill(tty); } tty_ldisc_unlock(tty); - if (reset) - tty_reset_termios(tty); - - tty_ldisc_debug(tty, "%p: re-opened\n", tty->ldisc); } /** @@ -719,44 +752,26 @@ void tty_ldisc_hangup(struct tty_struct *tty) int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) { - struct tty_ldisc *ld = tty->ldisc; - int retval; - - retval = tty_ldisc_open(tty, ld); + int retval = tty_ldisc_open(tty, tty->ldisc); if (retval) return retval; if (o_tty) { retval = tty_ldisc_open(o_tty, o_tty->ldisc); if (retval) { - tty_ldisc_close(tty, ld); + tty_ldisc_close(tty, tty->ldisc); return retval; } } 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 (or one end of pty pair) * * Called during the final close of a tty or a pty pair in order to shut - * down the line discpline layer. On exit, each ldisc assigned is N_TTY and - * each ldisc has not been opened. + * down the line discpline layer. On exit, each tty's ldisc is NULL. */ void tty_ldisc_release(struct tty_struct *tty) @@ -797,7 +812,7 @@ void tty_ldisc_init(struct tty_struct *tty) } /** - * tty_ldisc_init - ldisc cleanup for new tty + * tty_ldisc_deinit - ldisc cleanup for new tty * @tty: tty that was allocated recently * * The tty structure must not becompletely set up (tty_ldisc_setup) when @@ -805,12 +820,7 @@ void tty_ldisc_init(struct tty_struct *tty) */ void tty_ldisc_deinit(struct tty_struct *tty) { - tty_ldisc_put(tty->ldisc); + if (tty->ldisc) + tty_ldisc_put(tty->ldisc); tty->ldisc = NULL; } - -void tty_ldisc_begin(void) -{ - /* Setup the default TTY line discipline. */ - (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); -} |