RE: x86/mce: suspicious RCU usage in 4.13.4

[Luck, Tony]

> here's a second attempt at a more rigorous simplification: RCU stuff is
> gone and only a single loop scans through the elements.

The dev_mce_log() changes look good now.

You can apply the axe to more bits of mce_chrdev_read() though. Like that

	while (!m->finished) {

we hold the mutex, the writer of that holds the mutex ... the spin loop is going to always
time out.  

-Tony