From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752608AbaHDKkF (ORCPT ); Mon, 4 Aug 2014 06:40:05 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:38193 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752589AbaHDKkB (ORCPT ); Mon, 4 Aug 2014 06:40:01 -0400 Message-Id: <20140804103537.564978189@infradead.org> User-Agent: quilt/0.60-1 Date: Mon, 04 Aug 2014 12:30:29 +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, Eric Paris , John McCutchan , Robert Love , Peter Zijlstra Subject: [RFC][PATCH 4/7] inotify: Deal with nested sleeps References: <20140804103025.478913141@infradead.org> Content-Disposition: inline; filename=peterz-might_sleep-inotify.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org inotify_read is a wait loop 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: Eric Paris Cc: John McCutchan Cc: Robert Love Signed-off-by: Peter Zijlstra --- fs/notify/inotify/inotify_user.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -227,14 +227,13 @@ static ssize_t inotify_read(struct file struct fsnotify_event *kevent; char __user *start; int ret; - DEFINE_WAIT(wait); + DEFINE_WAIT_FUNC(wait, woken_wake_function); start = buf; group = file->private_data; + add_wait_queue(&group->notification_waitq, &wait); while (1) { - prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE); - mutex_lock(&group->notification_mutex); kevent = get_one_event(group, count); mutex_unlock(&group->notification_mutex); @@ -264,10 +263,10 @@ static ssize_t inotify_read(struct file if (start != buf) break; - schedule(); + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); } + remove_wait_queue(&group->notification_waitq, &wait); - finish_wait(&group->notification_waitq, &wait); if (start != buf && ret != -EFAULT) ret = buf - start; return ret;