From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752546AbaHDKj5 (ORCPT ); Mon, 4 Aug 2014 06:39:57 -0400 Received: from casper.infradead.org ([85.118.1.10]:33291 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752216AbaHDKjy (ORCPT ); Mon, 4 Aug 2014 06:39:54 -0400 Message-Id: <20140804103537.628164803@infradead.org> User-Agent: quilt/0.60-1 Date: Mon, 04 Aug 2014 12:30:30 +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, Greg Kroah-Hartman , Jiri Slaby , Peter Zijlstra Subject: [RFC][PATCH 5/7] tty: Deal with nested sleeps References: <20140804103025.478913141@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 and the wait loop breaks the sleep functions that assume TASK_RUNNING (mutex_lock). 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: Greg Kroah-Hartman Cc: Jiri Slaby Signed-off-by: Peter Zijlstra --- 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);