From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754365AbaIXIjB (ORCPT ); Wed, 24 Sep 2014 04:39:01 -0400 Received: from casper.infradead.org ([85.118.1.10]:38736 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751680AbaIXI1M (ORCPT ); Wed, 24 Sep 2014 04:27:12 -0400 Message-Id: <20140924082242.323011233@infradead.org> User-Agent: quilt/0.60-1 Date: Wed, 24 Sep 2014 10:18:51 +0200 From: Peter Zijlstra To: mingo@kernel.org, oleg@redhat.com, torvalds@linux-foundation.org Cc: tglx@linutronix.de, ilya.dryomov@inktank.com, umgwanakikbuti@gmail.com, linux-kernel@vger.kernel.org, Peter Zijlstra , Jiri Slaby , Greg Kroah-Hartman Subject: [PATCH 06/11] tty: Deal with nested sleeps References: <20140924081845.572814794@infradead.org> Content-Disposition: inline; filename=peterz-might_sleep-tty.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org n_tty_{read,write} are wait loops with sleeps in. Wait loops rely on task_struct::state and sleeps do too, since that's the only means of actually sleeping. Therefore the nested sleeps destroy the wait loop state. Fix this by using the new woken_wake_function and wait_woken() stuff, which registers wakeups in wait and thereby allows shrinking the task_state::state changes to the actual sleep part. Cc: Jiri Slaby Acked-by: Greg Kroah-Hartman Signed-off-by: Peter Zijlstra (Intel) --- drivers/tty/n_tty.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2123,7 +2123,7 @@ static ssize_t n_tty_read(struct tty_str { struct n_tty_data *ldata = tty->disc_data; unsigned char __user *b = buf; - DECLARE_WAITQUEUE(wait, current); + DEFINE_WAIT_FUNC(wait, woken_wake_function); int c; int minimum, time; ssize_t retval = 0; @@ -2186,10 +2186,6 @@ static ssize_t n_tty_read(struct tty_str nr--; break; } - /* This statement must be first before checking for input - so that any interrupt will set the state back to - TASK_RUNNING. */ - set_current_state(TASK_INTERRUPTIBLE); if (((minimum - (b - buf)) < ldata->minimum_to_wake) && ((minimum - (b - buf)) >= 1)) @@ -2220,13 +2216,13 @@ static ssize_t n_tty_read(struct tty_str n_tty_set_room(tty); up_read(&tty->termios_rwsem); - timeout = schedule_timeout(timeout); + timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, + timeout); down_read(&tty->termios_rwsem); continue; } } - __set_current_state(TASK_RUNNING); /* Deal with packet mode. */ if (packet && b == buf) { @@ -2273,7 +2269,6 @@ static ssize_t n_tty_read(struct tty_str mutex_unlock(&ldata->atomic_read_lock); - __set_current_state(TASK_RUNNING); if (b - buf) retval = b - buf; @@ -2306,7 +2301,7 @@ static ssize_t n_tty_write(struct tty_st const unsigned char *buf, size_t nr) { const unsigned char *b = buf; - DECLARE_WAITQUEUE(wait, current); + DEFINE_WAIT_FUNC(wait, woken_wake_function); int c; ssize_t retval = 0; @@ -2324,7 +2319,6 @@ static ssize_t n_tty_write(struct tty_st add_wait_queue(&tty->write_wait, &wait); while (1) { - set_current_state(TASK_INTERRUPTIBLE); if (signal_pending(current)) { retval = -ERESTARTSYS; break; @@ -2378,12 +2372,11 @@ static ssize_t n_tty_write(struct tty_st } up_read(&tty->termios_rwsem); - schedule(); + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); down_read(&tty->termios_rwsem); } break_out: - __set_current_state(TASK_RUNNING); remove_wait_queue(&tty->write_wait, &wait); if (b - buf != nr && tty->fasync) set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);