uevent: send events in correct order according to seqnum (v3)

uevent: send events in correct order according to seqnum (v3)

commit 7b60a18da393ed70db043a777fd9e6d5363077c4 upstream.

The queue handling in the udev daemon assumes that the events are
ordered.

Before this patch uevent_seqnum is incremented under sequence_lock,
than an event is send uner uevent_sock_mutex. I want to say that code
contained a window between incrementing seqnum and sending an event.

This patch locks uevent_sock_mutex before incrementing uevent_seqnum.

v2: delete sequence_lock, uevent_seqnum is protected by uevent_sock_mutex
v3: unlock the mutex before the goto exit

Thanks for Kay for the comments.

Signed-off-by: Andrew Vagin <avagin@openvz.org>
Tested-By: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>