x86/mce: Make timer handling more robust

Erik reported that on a preproduction hardware a CMCI storm triggers the
BUG_ON in add_timer_on(). The reason is that the per CPU MCE timer is
started by the CMCI logic before the MCE CPU hotplug callback starts the
timer with add_timer_on(). So the timer is already queued which triggers
the BUG.

Using add_timer_on() is pretty pointless in this code because the timer is
strictlty per CPU, initialized as pinned and all operations which arm the
timer happen on the CPU to which the timer belongs.

Simplify the whole machinery by using mod_timer() instead of add_timer_on()
which avoids the problem because mod_timer() can handle already queued
timers. Use __start_timer() everywhere so the earliest armed expiry time is
preserved.

Reported-by: Erik Veijola <erik.veijola@intel.com>
Tested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701310936080.3457@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

path: root/net/lapb/Kconfig

#
# LAPB Data Link Drive
#

config LAPB
	tristate "LAPB Data Link Driver"
	---help---
	  Link Access Procedure, Balanced (LAPB) is the data link layer (i.e.
	  the lower) part of the X.25 protocol. It offers a reliable
	  connection service to exchange data frames with one other host, and
	  it is used to transport higher level protocols (mostly X.25 Packet
	  Layer, the higher part of X.25, but others are possible as well).
	  Usually, LAPB is used with specialized X.21 network cards, but Linux
	  currently supports LAPB only over Ethernet connections. If you want
	  to use LAPB connections over Ethernet, say Y here and to "LAPB over
	  Ethernet driver" below. Read
	  <file:Documentation/networking/lapb-module.txt> for technical
	  details.

	  To compile this driver as a module, choose M here: the
	  module will be called lapb.  If unsure, say N.