mdraid6 problem post 3.5.0

[John Drescher]

For the last few weeks I have been doing some reliability testing on a
 mdraid6 array. One of my test was to physically hot remove a raid
member disk. This worked flawlessly with gentoo-sources-3.5.0 for the
5 or so times I tried it with my 12 disk + 1 spare mdraid6 array.
After pulling a disk a few seconds later the array automatically
rebuilds with a spare and after finishing all data checks out via
btrfs a scrub. However trying this with gentoo-sources-3.5.2 or the
latest kernel.org git sources the machine does not start the rebuild
and any access to /proc/mdstat or and disk access that is not in cache
for that array just leads to an a long (possibly infinite) wait
eventually forcing me to have to use the reset button when the sysrq
key combinations fail to shut down the machine. I do see some kernel
debug message in the console alt-ctrl-f12 but I was unable to save
that to copy.

Is this a known problem? If not it may be possible that I could bisect
this next week to the patch that causes this behavior.

-- 
John M. Drescher
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