HID: hiddev: fix nonblocking read semantics wrt EIO/ERESTARTSYS

When the file has been open in non-blocking mode, EIO or ERESTARTSYS
would never be returned even if they should (for example when device
has been unplugged, you want EIO and not EAGAIN to be returned).

Move the O_NONBLOCK check after other checks have been performed.

Base on similar patch done to hidraw by
Founder Fang <founder.fang@gmail.com>

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 711c9656ec0..87bd64959a9 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -361,10 +361,6 @@ static ssize_t hiddev_read(struct file * file, char __user * buffer, size_t coun
                         prepare_to_wait(&list->hiddev->wait, &wait, TASK_INTERRUPTIBLE);
 
                         while (list->head == list->tail) {
-                                if (file->f_flags & O_NONBLOCK) {
-                                        retval = -EAGAIN;
-                                        break;
-                                }
                                 if (signal_pending(current)) {
                                         retval = -ERESTARTSYS;
                                         break;
@@ -373,6 +369,10 @@ static ssize_t hiddev_read(struct file * file, char __user * buffer, size_t coun
                                         retval = -EIO;
                                         break;
                                 }
+                                if (file->f_flags & O_NONBLOCK) {
+                                        retval = -EAGAIN;
+                                        break;
+                                }
 
                                 /* let O_NONBLOCK tasks run */
                                 mutex_unlock(&list->thread_lock);