The following calltrace is possible now:
handle_sysrq
machine_emergency_restart
mach_reboot_fixups
pci_get_device
pci_get_subsys
down_read
The patch skips reboot fixup if called from sysrq-B code.
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>