From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938682AbcIERVA (ORCPT ); Mon, 5 Sep 2016 13:21:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:52773 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935827AbcIEQwf (ORCPT ); Mon, 5 Sep 2016 12:52:35 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Brian Norris , Lars-Peter Clausen , Jonathan Cameron Subject: [PATCH 4.7 075/143] iio: fix sched WARNING "do not call blocking ops when !TASK_RUNNING" Date: Mon, 5 Sep 2016 18:44:11 +0200 Message-Id: <20160905164433.780458810@linuxfoundation.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20160905164430.593075551@linuxfoundation.org> References: <20160905164430.593075551@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: Brian Norris commit fcf68f3c0bb2a541aa47a2a38b8939edf84fd529 upstream. When using CONFIG_DEBUG_ATOMIC_SLEEP, the scheduler nicely points out that we're calling sleeping primitives within the wait_event loop, which means we might clobber the task state: [ 10.831289] do not call blocking ops when !TASK_RUNNING; state=1 set at [] [ 10.845531] ------------[ cut here ]------------ [ 10.850161] WARNING: at kernel/sched/core.c:7630 ... [ 12.164333] ---[ end trace 45409966a9a76438 ]--- [ 12.168942] Call trace: [ 12.171391] [] __might_sleep+0x64/0x90 [ 12.176699] [] mutex_lock_nested+0x50/0x3fc [ 12.182440] [] iio_kfifo_buf_data_available+0x28/0x4c [ 12.189043] [] iio_buffer_ready+0x60/0xe0 [ 12.194608] [] iio_buffer_read_first_n_outer+0x108/0x1a8 [ 12.201474] [] __vfs_read+0x58/0x114 [ 12.206606] [] vfs_read+0x94/0x118 [ 12.211564] [] SyS_read+0x64/0xb4 [ 12.216436] [] el0_svc_naked+0x24/0x28 To avoid this, we should (a la https://lwn.net/Articles/628628/) use the wait_woken() function, which avoids the nested sleeping while still handling races between waiting / wake-events. Signed-off-by: Brian Norris Reviewed-by: Lars-Peter Clausen Signed-off-by: Jonathan Cameron Signed-off-by: Greg Kroah-Hartman --- drivers/iio/industrialio-buffer.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -107,6 +107,7 @@ ssize_t iio_buffer_read_first_n_outer(st { struct iio_dev *indio_dev = filp->private_data; struct iio_buffer *rb = indio_dev->buffer; + DEFINE_WAIT_FUNC(wait, woken_wake_function); size_t datum_size; size_t to_wait; int ret; @@ -131,19 +132,29 @@ ssize_t iio_buffer_read_first_n_outer(st else to_wait = min_t(size_t, n / datum_size, rb->watermark); + add_wait_queue(&rb->pollq, &wait); do { - ret = wait_event_interruptible(rb->pollq, - iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)); - if (ret) - return ret; - - if (!indio_dev->info) - return -ENODEV; + if (!indio_dev->info) { + ret = -ENODEV; + break; + } + + if (!iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)) { + if (signal_pending(current)) { + ret = -ERESTARTSYS; + break; + } + + wait_woken(&wait, TASK_INTERRUPTIBLE, + MAX_SCHEDULE_TIMEOUT); + continue; + } ret = rb->access->read_first_n(rb, n, buf); if (ret == 0 && (filp->f_flags & O_NONBLOCK)) ret = -EAGAIN; } while (ret == 0); + remove_wait_queue(&rb->pollq, &wait); return ret; }