From 536ebe9ca999f6d0903d91698678ccc1742e8dd9 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 16 Dec 2014 16:28:38 +0100 Subject: sched, fanotify: Deal with nested sleeps As per e23738a7300a ("sched, inotify: Deal with nested sleeps"). fanotify_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. Reported-by: Yuanhan Liu Reported-by: Sedat Dilek Signed-off-by: Peter Zijlstra (Intel) Cc: Takashi Iwai Cc: Al Viro Cc: Eric Paris Cc: Linus Torvalds Cc: Eric Paris Link: http://lkml.kernel.org/r/20141216152838.GZ3337@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- fs/notify/fanotify/fanotify_user.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'fs') diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index c991616acca9..bff8567aa42d 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -259,16 +259,15 @@ static ssize_t fanotify_read(struct file *file, char __user *buf, 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; pr_debug("%s: group=%p\n", __func__, group); + 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); @@ -289,7 +288,8 @@ static ssize_t fanotify_read(struct file *file, char __user *buf, if (start != buf) break; - schedule(); + + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); continue; } @@ -318,8 +318,8 @@ static ssize_t fanotify_read(struct file *file, char __user *buf, buf += ret; count -= ret; } + remove_wait_queue(&group->notification_waitq, &wait); - finish_wait(&group->notification_waitq, &wait); if (start != buf && ret != -EFAULT) ret = buf - start; return ret; -- cgit v1.2.3-55-g7522