Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758003AbbBFMZE (ORCPT ); Fri, 6 Feb 2015 07:25:04 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:41109 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753303AbbBFMCV (ORCPT ); Fri, 6 Feb 2015 07:02:21 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Francesco Ruggeri , Greg Kroah-Hartman , Luis Henriques Subject: [PATCH 3.16.y-ckt 064/135] tty: Fix pty master poll() after slave closes v2 Date: Fri, 6 Feb 2015 12:00:42 +0000 Message-Id: <1423224113-10958-65-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1423224113-10958-1-git-send-email-luis.henriques@canonical.com> References: <1423224113-10958-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2623 Lines: 77 3.16.7-ckt6 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Francesco Ruggeri commit c4dc304677e8d566572c4738d95c48be150c6606 upstream. Commit f95499c3030f ("n_tty: Don't wait for buffer work in read() loop") introduces a race window where a pty master can be signalled that the pty slave was closed before all the data that the slave wrote is delivered. Commit f8747d4a466a ("tty: Fix pty master read() after slave closes") fixed the problem in case of n_tty_read, but the problem still exists for n_tty_poll. This can be seen by running 'for ((i=0; i<100;i++));do ./test.py ;done' where test.py is: import os, select, pty (pid, pty_fd) = pty.fork() if pid == 0: os.write(1, 'This string should be received by parent') else: poller = select.epoll() poller.register( pty_fd, select.EPOLLIN ) ready = poller.poll( 1 * 1000 ) for fd, events in ready: if not events & select.EPOLLIN: print 'missed POLLIN event' else: print os.read(fd, 100) poller.close() The string from the slave is missed several times. This patch takes the same approach as the fix for read and special cases this condition for poll. Tested on 3.16. Signed-off-by: Francesco Ruggeri Signed-off-by: Greg Kroah-Hartman Signed-off-by: Luis Henriques --- drivers/tty/n_tty.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index d31b4a8c02ab..662cbb3af586 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2414,12 +2414,17 @@ static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file, poll_wait(file, &tty->read_wait, wait); poll_wait(file, &tty->write_wait, wait); + if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) + mask |= POLLHUP; if (input_available_p(tty, 1)) mask |= POLLIN | POLLRDNORM; + else if (mask & POLLHUP) { + tty_flush_to_ldisc(tty); + if (input_available_p(tty, 1)) + mask |= POLLIN | POLLRDNORM; + } if (tty->packet && tty->link->ctrl_status) mask |= POLLPRI | POLLIN | POLLRDNORM; - if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) - mask |= POLLHUP; if (tty_hung_up_p(file)) mask |= POLLHUP; if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) { -- 2.1.4 -- 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/