diff options
Diffstat (limited to 'drivers/char/tty_ldisc.c')
| -rw-r--r-- | drivers/char/tty_ldisc.c | 78 |
1 files changed, 52 insertions, 26 deletions
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c index aafdbaebc16a..500e740ec5e4 100644 --- a/drivers/char/tty_ldisc.c +++ b/drivers/char/tty_ldisc.c @@ -34,6 +34,8 @@ #include <linux/vt_kern.h> #include <linux/selection.h> +#include <linux/smp_lock.h> /* For the moment */ + #include <linux/kmod.h> #include <linux/nsproxy.h> @@ -443,8 +445,14 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num) 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); + 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; } @@ -518,7 +526,7 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) static int tty_ldisc_halt(struct tty_struct *tty) { clear_bit(TTY_LDISC, &tty->flags); - return cancel_delayed_work(&tty->buf.work); + return cancel_delayed_work_sync(&tty->buf.work); } /** @@ -545,6 +553,7 @@ int tty_set_ldisc(struct tty_struct *tty, int 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. @@ -558,10 +567,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) */ 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 @@ -582,6 +593,9 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); mutex_lock(&tty->ldisc_mutex); } + + lock_kernel(); + set_bit(TTY_LDISC_CHANGING, &tty->flags); /* @@ -592,6 +606,8 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) tty->receive_room = 0; o_ldisc = tty->ldisc; + + unlock_kernel(); /* * Make sure we don't change while someone holds a * reference to the line discipline. The TTY_LDISC bit @@ -617,12 +633,14 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) 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; } @@ -664,6 +682,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) if (o_work) schedule_delayed_work(&o_tty->buf.work, 1); mutex_unlock(&tty->ldisc_mutex); + unlock_kernel(); return retval; } @@ -687,12 +706,13 @@ 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 * - * Switch the tty back to N_TTY line discipline and leave the - * ldisc state closed + * Switch the tty to a line discipline and leave the ldisc + * state closed */ -static void tty_ldisc_reinit(struct tty_struct *tty) +static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc) { struct tty_ldisc *ld; @@ -702,10 +722,10 @@ static void tty_ldisc_reinit(struct tty_struct *tty) /* * Switch the line discipline back */ - ld = tty_ldisc_get(N_TTY); + ld = tty_ldisc_get(ldisc); BUG_ON(IS_ERR(ld)); tty_ldisc_assign(tty, ld); - tty_set_termios_ldisc(tty, N_TTY); + tty_set_termios_ldisc(tty, ldisc); } /** @@ -726,6 +746,8 @@ static void tty_ldisc_reinit(struct tty_struct *tty) 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 @@ -753,28 +775,32 @@ void tty_ldisc_hangup(struct tty_struct *tty) wake_up_interruptible_poll(&tty->read_wait, POLLIN); /* * Shutdown the current line discipline, and reset it to - * N_TTY. + * N_TTY if need be. + * + * Avoid racing set_ldisc or tty_ldisc_release */ - if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) { - /* Make sure the old ldisc is quiescent */ - tty_ldisc_halt(tty); - flush_scheduled_work(); - - /* Avoid racing set_ldisc or tty_ldisc_release */ - mutex_lock(&tty->ldisc_mutex); - if (tty->ldisc) { /* Not yet closed */ - /* 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 */ + 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); - tty_reset_termios(tty); + tty_ldisc_enable(tty); } + mutex_unlock(&tty->ldisc_mutex); + if (reset) + tty_reset_termios(tty); } /** |