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

Discription:
	In RAID5 array, if a drive is removed during initialization and the same time if IO is happening to that md. 
	Then IO is getting struck, and md_raid5 thread is using 100 % of CPU. Also the md state showing as resync=PENDING

Kernel :  Issue found in the following kernels
	>RHEL 6.5 (2.6.32-431.el6.x86_64)
    >CentOS 7 (kernel-3.10.0-123.13.1.el7.x86_64)

Steps to Reproduce the issue:
	1. Created a raid 5 md with 4 drives using the below mdadm command.
		mdadm -C /dev/md0 -c 64 -l 5 -f -n 4 -e 1.2 /dev/sdb6 /dev/sdc6 /dev/sdd6 /dev/sde6
	2. Make the md writable
		mdadm –readwrite /dev/md0
	3. Now md will start initialization
	4. Run FIO Tool, the the below said configuration
		/usr/bin/fio --name=md0 --filename=/dev/md0 --thread --numjobs=10 --direct=1 --group_reporting --unlink=0 --loops=1 --offset=0 --randrepeat=1 --norandommap --scramble_buffers=1 --stonewall --ioengine=libaio --rw=randwrite --bs=8704 --iodepth=4000 --runtime=3000 --blockalign=512
	4. During MD initialzing, remove a drive(either using MDADM set faulty/remove or remove manually)
	5. Now the IO will struck, and cat /proc/mdstat shows states with resync=PENDING

Step done one by one to reproduce the issue, and the Observation during each step:

1. System Information:
	[root@root ~]# uname -a
		Linux root 2.6.32-431.el6.x86_64 #1 SMP Sun Nov 10 22:19:54 EST 2013 x86_64 x86_64 x86_64 GNU/Linux
	[root@root ~]# mdadm -V
		mdadm - v3.2.6 - 25th October 2012
	[root@root ~]# fio --version
		fio-2.1.10
	[root@root ~]# lsscsi
		[0:0:0:0]    disk    SEAGATE  ST31000640SS     0003  /dev/sda
		[0:0:1:0]    disk    SEAGATE  ST2000NM0001     0002  /dev/sdb
		[0:0:2:0]    enclosu LSI CORP SAS2X36          0424  -
		[0:0:3:0]    disk    SEAGATE  ST200FM0002      0003  /dev/sdc
		[0:0:4:0]    disk    SEAGATE  ST200FM0002      0003  /dev/sdd
		[0:0:5:0]    disk    SEAGATE  ST200FM0002      0003  /dev/sde
		[0:0:6:0]    disk    SEAGATE  ST200FM0002      0003  /dev/sdf

2. Creating raid5 md
	[root@root ~]# mdadm -C /dev/md0 -c 64 -l 5 -f -n 4 -e 1.2 /dev/sd[cdef]6
		mdadm: /dev/sdc6 appears to be part of a raid array:
			level=raid5 devices=4 ctime=Mon Dec 15 18:23:17 2014
		mdadm: /dev/sdd6 appears to be part of a raid array:
			level=raid5 devices=4 ctime=Mon Dec 15 18:23:17 2014
		mdadm: /dev/sde6 appears to be part of a raid array:
			level=raid5 devices=4 ctime=Mon Dec 15 18:23:17 2014
		mdadm: /dev/sdf6 appears to be part of a raid array:
			level=raid5 devices=4 ctime=Mon Dec 15 18:23:17 2014
		Continue creating array? y
		mdadm: array /dev/md0 started.

	dmesg
		md: unbind<sdf6>
		md: export_rdev(sdf6)
		md: unbind<sde6>
		md: export_rdev(sde6)
		md: unbind<sdd6>
		md: export_rdev(sdd6)
		md: unbind<sdc6>
		md: export_rdev(sdc6)
		md: bind<sdc6>
		md: bind<sdd6>
		md: bind<sde6>
		md: bind<sdf6>
		async_tx: api initialized (async)
		xor: automatically using best checksumming function: generic_sse
		   generic_sse:  9976.000 MB/sec
		xor: using function: generic_sse (9976.000 MB/sec)
		raid6: sse2x1    6386 MB/s
		raid6: sse2x2    7464 MB/s
		raid6: sse2x4    8199 MB/s
		raid6: using algorithm sse2x4 (8199 MB/s)
		raid6: using ssse3x2 recovery algorithm
		md: raid6 personality registered for level 6
		md: raid5 personality registered for level 5
		md: raid4 personality registered for level 4
		bio: create slab <bio-1> at 1
		md/raid:md0: not clean -- starting background reconstruction
		md/raid:md0: device sdf6 operational as raid disk 3
		md/raid:md0: device sde6 operational as raid disk 2
		md/raid:md0: device sdd6 operational as raid disk 1
		md/raid:md0: device sdc6 operational as raid disk 0
		md/raid:md0: allocated 4314kB
		md/raid:md0: raid level 5 active with 4 out of 4 devices, algorithm 2
		RAID conf printout:
		--- level:5 rd:4 wd:4
		disk 0, o:1, dev:sdc6
		disk 1, o:1, dev:sdd6
		disk 2, o:1, dev:sde6
		disk 3, o:1, dev:sdf6
		md0: detected capacity change from 0 to 576636125184
		md: resync of RAID array md0
		md: minimum _guaranteed_  speed: 1000 KB/sec/disk.
		md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for resync.
		md: using 128k window, over a total of 187707072k.
		md0: unknown partition table

	[root@root ~]# cat /proc/mdstat
		Personalities : [raid6] [raid5] [raid4]
		md0 : active raid5 sdf6[3] sde6[2] sdd6[1] sdc6[0]
			  563121216 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]
			  [=>...................]  resync =  8.2% (15404908/187707072) finish=16.6min speed=172462K/sec

		unused devices: <none>

	[root@root ~]# echo 10000 > /sys/block/md0/md/sync_speed_min
	[root@root ~]# echo 30000 > /sys/block/md0/md/sync_speed_max

	[root@root ~]# cat /proc/mdstat
		Personalities : [raid6] [raid5] [raid4]
		md0 : active raid5 sdf6[3] sde6[2] sdd6[1] sdc6[0]
			  563121216 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]
			  [===>.................]  resync = 16.1% (30226432/187707072) finish=47.3min speed=55459K/sec

		unused devices: <none>

3. Start FIO
	[root@root ~]# /usr/bin/fio --name=md0 --filename=/dev/md0 --thread --numjobs=10 --direct=1 --group_reporting --unlink=0 --loops=1 --offset=0 --randrepeat=1 --norandommap --scramble_buffers=1 --stonewall --ioengine=libaio --rw=randwrite --bs=8704 --iodepth=4000 --runtime=3000 --blockalign=512
		md0: (g=0): rw=randwrite, bs=8704-8704/8704-8704/8704-8704, ioengine=libaio, iodepth=4000
		...
		fio-2.1.10
		Starting 10 threads
		Jobs: 10 (f=10): [wwwwwwwwww] [12.8% done] [0KB/0KB/0KB /s] [0/0/0 iops] [eta 43m:37s]

4. Remove a drive from md arry using mdadm command
[root@root ~]# mdadm /dev/md0 --set-faulty /dev/sdc6

	dmesg
		md/raid:md0: Disk failure on sdc6, disabling device.
		md/raid:md0: Operation continuing on 3 devices.
		md: md0: resync done.
		md: checkpointing resync of md0.

5. System state after the drive is removed
	[root@root ~]# cat /proc/mdstat
		Personalities : [raid6] [raid5] [raid4]
		md0 : active raid5 sdf6[3] sde6[2] sdd6[1] sdc6[0](F)
			  563121216 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/3] [_UUU]
				resync=PENDING

		unused devices: <none>

	top

		top - 17:55:06 up  1:09,  3 users,  load average: 11.98, 8.53, 3.99
		Tasks: 313 total,   2 running, 311 sleeping,   0 stopped,   0 zombie
		Cpu(s):  0.0%us,  6.3%sy,  0.0%ni, 93.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
		Mem:  16455916k total,   780184k used, 15675732k free,    29628k buffers
		Swap:  6127608k total,        0k used,  6127608k free,   116212k cached

		  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
		2690 root      20   0     0    0    0 R 100.0  0.0   6:44.41 md0_raid5
		  235 root      39  19     0    0    0 S  0.3  0.0   0:12.95 kipmi0
		2650 root      20   0 98.1m 4456 3348 S  0.3  0.0   0:00.21 sshd
			1 root      20   0 19364 1536 1232 S  0.0  0.0   0:01.42 init

	Dmesg

		INFO: task fio:2715 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 000000000000000a     0  2715   2654 0x00000080
		ffff88043b623598 0000000000000082 0000000000000000 ffffffff81058d53
		ffff88043b623548 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff88043b40b098 ffff88043b623fd8 000000000000fbc8 ffff88043b40b098
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff8140fa39>] ? md_wakeup_thread+0x39/0x70
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffffa0308f66>] ? make_request+0x306/0xc6c [raid456]
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81122283>] ? mempool_alloc+0x63/0x140
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c767a>] do_direct_IO+0x7ca/0xfa0
		[<ffffffff811c8196>] __blockdev_direct_IO_newtrunc+0x346/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2717 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000004     0  2717   2654 0x00000080
		ffff880439e97698 0000000000000082 ffff880439e97628 ffffffff81058d53
		ffff880439e97648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff88043b0adab8 ffff880439e97fd8 000000000000fbc8 ffff88043b0adab8
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8e50>] __blockdev_direct_IO_newtrunc+0x1000/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2718 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000005     0  2718   2654 0x00000080
		ffff88043bc13698 0000000000000082 ffff88043bc13628 ffffffff81058d53
		ffff88043bc13648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff88043b0ad058 ffff88043bc13fd8 000000000000fbc8 ffff88043b0ad058
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8e50>] __blockdev_direct_IO_newtrunc+0x1000/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2719 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000001     0  2719   2654 0x00000080
		ffff880439ebb698 0000000000000082 ffff880439ebb628 ffffffff81058d53
		ffff880439ebb648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff88043b0ac5f8 ffff880439ebbfd8 000000000000fbc8 ffff88043b0ac5f8
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8acd>] __blockdev_direct_IO_newtrunc+0xc7d/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2720 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000008     0  2720   2654 0x00000080
		ffff88043b8cf698 0000000000000082 ffff88043b8cf628 ffffffff81058d53
		ffff88043b8cf648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff880439e89af8 ffff88043b8cffd8 000000000000fbc8 ffff880439e89af8
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8acd>] __blockdev_direct_IO_newtrunc+0xc7d/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2721 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000000     0  2721   2654 0x00000080
		ffff88043b047698 0000000000000082 ffff88043b047628 ffffffff81058d53
		ffff88043b047648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff880439e89098 ffff88043b047fd8 000000000000fbc8 ffff880439e89098
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8acd>] __blockdev_direct_IO_newtrunc+0xc7d/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2722 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000000     0  2722   2654 0x00000080
		ffff880439ea3698 0000000000000082 ffff880439ea3628 ffffffff81058d53
		ffff880439ea3648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff880439e88638 ffff880439ea3fd8 000000000000fbc8 ffff880439e88638
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8acd>] __blockdev_direct_IO_newtrunc+0xc7d/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2723 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000006     0  2723   2654 0x00000080
		ffff88043bf5f698 0000000000000082 ffff88043bf5f628 ffffffff81058d53
		ffff88043bf5f648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff88043a183ab8 ffff88043bf5ffd8 000000000000fbc8 ffff88043a183ab8
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8acd>] __blockdev_direct_IO_newtrunc+0xc7d/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2724 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 000000000000000b     0  2724   2654 0x00000080
		ffff88043be05698 0000000000000082 ffff88043be05628 ffffffff81058d53
		ffff88043be05648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff88043a183058 ffff88043be05fd8 000000000000fbc8 ffff88043a183058
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8acd>] __blockdev_direct_IO_newtrunc+0xc7d/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
		INFO: task fio:2725 blocked for more than 120 seconds.
			  Not tainted 2.6.32-431.el6.x86_64 #1
		"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
		fio           D 0000000000000003     0  2725   2654 0x00000080
		ffff88043be07698 0000000000000082 ffff88043be07628 ffffffff81058d53
		ffff88043be07648 ffff880230e49cc0 ffff8802389aa228 ffff88043b2ad1b8
		ffff88043a1825f8 ffff88043be07fd8 000000000000fbc8 ffff88043a1825f8
		Call Trace:
		[<ffffffff81058d53>] ? __wake_up+0x53/0x70
		[<ffffffffa030334b>] ? md_raid5_unplug_device+0x7b/0x100 [raid456]
		[<ffffffffa0304146>] get_active_stripe+0x236/0x830 [raid456]
		[<ffffffff81065df0>] ? default_wake_function+0x0/0x20
		[<ffffffff8109b5ce>] ? prepare_to_wait+0x4e/0x80
		[<ffffffffa0308e15>] make_request+0x1b5/0xc6c [raid456]
		[<ffffffff8109b2a0>] ? autoremove_wake_function+0x0/0x40
		[<ffffffff811220e5>] ? mempool_alloc_slab+0x15/0x20
		[<ffffffff81415b41>] md_make_request+0xe1/0x230
		[<ffffffff811c3fd2>] ? bvec_alloc_bs+0x62/0x110
		[<ffffffff811c32f0>] ? __bio_add_page+0x110/0x230
		[<ffffffff81266c50>] generic_make_request+0x240/0x5a0
		[<ffffffff811c742c>] ? do_direct_IO+0x57c/0xfa0
		[<ffffffff81267020>] submit_bio+0x70/0x120
		[<ffffffff811c8acd>] __blockdev_direct_IO_newtrunc+0xc7d/0x1270
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c9137>] __blockdev_direct_IO+0x77/0xe0
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff811c53b7>] blkdev_direct_IO+0x57/0x60
		[<ffffffff811c4330>] ? blkdev_get_block+0x0/0x20
		[<ffffffff81120552>] generic_file_direct_write+0xc2/0x190
		[<ffffffff81121e71>] __generic_file_aio_write+0x3a1/0x490
		[<ffffffff811d64c0>] ? aio_read_evt+0xa0/0x170
		[<ffffffff811c490c>] blkdev_aio_write+0x3c/0xa0
		[<ffffffff811c48d0>] ? blkdev_aio_write+0x0/0xa0
		[<ffffffff811d4f64>] aio_rw_vect_retry+0x84/0x200
		[<ffffffff811d6924>] aio_run_iocb+0x64/0x170
		[<ffffffff811d7d51>] do_io_submit+0x291/0x920
		[<ffffffff811d83f0>] sys_io_submit+0x10/0x20
		[<ffffffff8100b072>] system_call_fastpath+0x16/0x1b

	[root@root ~]# cat /proc/2690/stack
		[<ffffffff810686da>] __cond_resched+0x2a/0x40
		[<ffffffffa030361c>] ops_run_io+0x2c/0x920 [raid456]
		[<ffffffffa03052cc>] handle_stripe+0x9cc/0x2980 [raid456]
		[<ffffffffa03078a4>] raid5d+0x624/0x850 [raid456]
		[<ffffffff81416f05>] md_thread+0x115/0x150
		[<ffffffff8109aef6>] kthread+0x96/0xa0
		[<ffffffff8100c20a>] child_rip+0xa/0x20
		[<ffffffffffffffff>] 0xffffffffffffffff

	[root@root ~]# cat /proc/2690/stat
		2690 (md0_raid5) R 2 0 0 0 -1 2149613632 0 0 0 0 0 68495 0 0 20 0 1 0 350990 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483391 256 0 0 0 17 2 0 0 6855 0 0
	[root@root ~]# cat /proc/2690/statm
		0 0 0 0 0 0 0
	[root@root ~]# cat /proc/2690/stat
		stat    statm   status
		[root@root ~]# cat /proc/2690/status
		Name:   md0_raid5
		State:  R (running)
		Tgid:   2690
		Pid:    2690
		PPid:   2
		TracerPid:      0
		Uid:    0       0       0       0
		Gid:    0       0       0       0
		Utrace: 0
		FDSize: 64
		Groups:
		Threads:        1
		SigQ:   2/128402
		SigPnd: 0000000000000000
		ShdPnd: 0000000000000000
		SigBlk: 0000000000000000
		SigIgn: fffffffffffffeff
		SigCgt: 0000000000000100
		CapInh: 0000000000000000
		CapPrm: ffffffffffffffff
		CapEff: fffffffffffffeff
		CapBnd: ffffffffffffffff
		Cpus_allowed:   ffffff
		Cpus_allowed_list:      0-23
		Mems_allowed:   00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000003
		Mems_allowed_list:      0-1
		voluntary_ctxt_switches:        5411612
		nonvoluntary_ctxt_switches:     257032