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sched, fanotify: Deal with nested sleeps

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As per e23738a730 ("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 <yuanhan.liu@linux.intel.com>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Paris <eparis@redhat.com>
Link: http://lkml.kernel.org/r/20141216152838.GZ3337@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-12-16 16:28:38 +01:00 committed by Ingo Molnar
parent b74e6278fd
commit 536ebe9ca9
1 changed files with 5 additions and 5 deletions
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10
fs/notify/fanotify/fanotify_user.c
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@ -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;