From f8747d4a466ab2cafe56112c51b3379f9fdb7a12 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Fri, 27 Sep 2013 13:27:05 -0400 Subject: tty: Fix pty master read() after slave closes Commit f95499c3030fe1bfad57745f2db1959c5b43dca8, n_tty: Don't wait for buffer work in read() loop creates a race window which can cause a pty master read() to miss the last pty slave write(s) and return -EIO instead, thus signalling the pty slave is closed. This can happen when the pty slave is written and immediately closed but before the tty buffer i/o loop receives the new input; the pty master read() is scheduled, sees its read buffer is empty and the pty slave has been closed, and exits. Because tty_flush_to_ldisc() has significant performance impact for parallel i/o, rather than revert the commit, special case this condition (ie., when the read buffer is empty and the 'other' pty has been closed) and, only then, wait for buffer work to complete before re-testing if the read buffer is still empty. As before, subsequent pty master reads return any available data until no more data is available, and then returns -EIO to indicate the pty slave has closed. Reported-by: Mikael Pettersson Signed-off-by: Peter Hurley Tested-by: Mikael Pettersson Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 46 ++++++++++++++++++++++++++-------------------- 1 file changed, 26 insertions(+), 20 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 01bf5eb4f238..7a744b69c3d1 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2183,28 +2183,34 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, if (!input_available_p(tty, 0)) { if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { - retval = -EIO; - break; - } - if (tty_hung_up_p(file)) - break; - if (!timeout) - break; - if (file->f_flags & O_NONBLOCK) { - retval = -EAGAIN; - break; - } - if (signal_pending(current)) { - retval = -ERESTARTSYS; - break; - } - n_tty_set_room(tty); - up_read(&tty->termios_rwsem); + up_read(&tty->termios_rwsem); + tty_flush_to_ldisc(tty); + down_read(&tty->termios_rwsem); + if (!input_available_p(tty, 0)) { + retval = -EIO; + break; + } + } else { + if (tty_hung_up_p(file)) + break; + if (!timeout) + break; + if (file->f_flags & O_NONBLOCK) { + retval = -EAGAIN; + break; + } + if (signal_pending(current)) { + retval = -ERESTARTSYS; + break; + } + n_tty_set_room(tty); + up_read(&tty->termios_rwsem); - timeout = schedule_timeout(timeout); + timeout = schedule_timeout(timeout); - down_read(&tty->termios_rwsem); - continue; + down_read(&tty->termios_rwsem); + continue; + } } __set_current_state(TASK_RUNNING); -- cgit v1.2.3 From a9fbf4d591da6cd1d3eaab826c7c15f77fc8f6a3 Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Tue, 1 Oct 2013 19:00:49 +0100 Subject: xen/hvc: allow xenboot console to be used again Commit d0380e6c3c0f6edb986d8798a23acfaf33d5df23 (early_printk: consolidate random copies of identical code) added in 3.10 introduced a check for con->index == -1 in early_console_register(). Initialize index to -1 for the xenboot console so earlyprintk=xen works again. Signed-off-by: David Vrabel Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/hvc/hvc_xen.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c index e61c36cbb866..c193af6a628f 100644 --- a/drivers/tty/hvc/hvc_xen.c +++ b/drivers/tty/hvc/hvc_xen.c @@ -636,6 +636,7 @@ struct console xenboot_console = { .name = "xenboot", .write = xenboot_write_console, .flags = CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME, + .index = -1, }; #endif /* CONFIG_EARLY_PRINTK */ -- cgit v1.2.3