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/ax25/TODO

Do the ax25_list_lock, ax25_dev_lock, linkfail_lockreally, ax25_frag_lock and
listen_lock have to be bh-safe?

Do the netrom and rose locks have to be bh-safe?

A device might be deleted after lookup in the SIOCADDRT ioctl but before it's
being used.

Routes to a device being taken down might be deleted by ax25_rt_device_down
but added by somebody else before the device has been deleted fully.

The ax25_rt_find_route synopsys is pervert but I somehow had to deal with
the race caused by the static variable in it's previous implementation.

Implement proper socket locking in netrom and rose.

Check socket locking when ax25_rcv is sending to raw sockets.  In particular
ax25_send_to_raw() seems fishy.  Heck - ax25_rcv is fishy.

Handle XID and TEST frames properly.