Messages in this thread Patch in this message | | | Subject | [PATCH]: Fix locking for tty drivers when doing urgent characters | From | Alan Cox <> | Date | Mon, 04 Sep 2006 14:45:41 +0100 |
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If you send a priority character (as is done for flow control) then the tty driver can either have its own method for "jumping the queue" or the characrer can be queued normally. In the latter case we call the write method but without the atomic_write_lock taken elsewhere.
Make this consistent. Note that the send_xchar method if implemented remains outside of the lock as it can jump ahead of a current write so must not be locked out by it.
Signed-off-by: Alan Cox <alan@redhat.com>
diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.18-rc5-mm1/drivers/char/tty_ioctl.c linux-2.6.18-rc5-mm1/drivers/char/tty_ioctl.c --- linux.vanilla-2.6.18-rc5-mm1/drivers/char/tty_ioctl.c 2006-09-01 13:39:04.000000000 +0100 +++ linux-2.6.18-rc5-mm1/drivers/char/tty_ioctl.c 2006-09-01 13:59:10.000000000 +0100 @@ -423,24 +628,28 @@ * * Send a high priority character to the tty even if stopped * - * Locking: none - * - * FIXME: overlapping calls with start/stop tty lose state of tty + * Locking: none for xchar method, write ordering for write method. */ -static void send_prio_char(struct tty_struct *tty, char ch) +static int send_prio_char(struct tty_struct *tty, char ch) { int was_stopped = tty->stopped; if (tty->driver->send_xchar) { tty->driver->send_xchar(tty, ch); - return; + return 0; } + + if (mutex_lock_interruptible(&tty->atomic_write_lock)) + return -ERESTARTSYS; + if (was_stopped) start_tty(tty); tty->driver->write(tty, &ch, 1); if (was_stopped) stop_tty(tty); + mutex_unlock(&tty->atomic_write_lock); + return 0; } int n_tty_ioctl(struct tty_struct * tty, struct file * file, @@ -514,11 +740,11 @@ break; case TCIOFF: if (STOP_CHAR(tty) != __DISABLED_CHAR) - send_prio_char(tty, STOP_CHAR(tty)); + return send_prio_char(tty, STOP_CHAR(tty)); break; case TCION: if (START_CHAR(tty) != __DISABLED_CHAR) - send_prio_char(tty, START_CHAR(tty)); + return send_prio_char(tty, START_CHAR(tty)); break; default: return -EINVAL; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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