Comment 12 for bug 1010926

Looks like I have the same problem on a Sony Vaio SVP132A1CL, ubuntustudio 14.04.3 LTS.

# uname -a:
Linux abc 3.16.0-53-lowlatency #72~14.04.1-Ubuntu SMP PREEMPT Fri Nov 6 19:22:01 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

# while : ; do cat /proc/acpi/button/lid/LID0/state ; sleep 1; done
state: open
state: open
state: closed
state: open

# dmesg | grep -i lid:
[ 0.681415] input: Lid Switch as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0D:00/input/input0
[ 0.681712] ACPI: Lid Switch [LID0]

# acpid -ldd:
Deprecated /proc/acpi/event was not found. Trying netlink and the input layer...
input layer /dev/input/event0 (Lid Switch) opened successfully, fd 4
input layer /dev/input/event1 (Power Button) opened successfully, fd 5
acpid: waiting for events: event logging is on
acpid: received input layer event "button/power PBTN 00000080 00000000"
[closing lid does nothing]

Interestingly, there are no other buttons defined in /proc/acpi/button/. There doesn't seem to be any activity on /dev/input/event0.

Workaround to lock screen on lid close (run in Settings manager/Session and start-up/Application Autostart):

#!/bin/sh
while :
do
 while grep -q close /proc/acpi/button/lid/LID0/state
  do sleep 5; done
 #echo "close->open"
 while grep -q open /proc/acpi/button/lid/LID0/state
  do sleep 1; done
 #echo "open->close"
 xflock4
done

Hope this helps.