Re: md_raid5 using 100% CPU and hang with status resync=PENDING, if a drive is removed during initialization

NeilBrown [off-list ref] writes:

On Mon, 2 Feb 2015 07:10:14 +0000 Manibalan P [off-list ref]
wrote:

quoted

Dear All,
	Any updates on this issue.

Probably the same as:

  http://marc.info/?l=linux-raid&m=142283560704091&w=2

Hi Neil,

I ran some tests on this one against the latest Linus' tree as of today
(1fa185ebcbcefdc5229c783450c9f0439a69f0c1) which I believe includes all
your pending 3.20 patches.

I am able to reproduce Manibalan's hangs on a system with 4 SSDs if I
run fio on top of a device while it is resyncing and I fail one of the
devices.

I can reproduce the issue for raid4 and raid5, but I don't see it if I
I use a raid6.

The following sequence consistently reproduces the problem for me:

mdadm -C /dev/md111 -f -e 1.2 -l5 -n4 /dev/sd[ghij]3
fio --name=md111 --filename=/dev/md111 --thread --numjobs=10 --direct=1 --group_reporting --unlink=0 --loops=1 --offset=0 --randrepeat=1 --norandommap --scramble_buffers=1 --stonewall --rw=randwrite --bs=8704 --iodepth=4000 --runtime=3000 --blockalign=512
mdadm /dev/md111 -f /dev/sdg3

Cheers,
Jes