sysrq should grab the tasklist lock, otherwise calling force_sig() is
not safe, as it might race with exiting task, which ->sighand might be
set to NULL already.
Signed-off-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>