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Re: [lkp-robot] [scsi, block] 0dba1314d4: WARNING:at_fs/sysfs/dir.c:#sysfs_warn_dup

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Dan Williams

unread,
Feb 4, 2017, 3:40:04 PM2/4/17
to
On Fri, Feb 3, 2017 at 11:09 PM, kernel test robot
<xiaol...@intel.com> wrote:
>
> FYI, we noticed the following commit:
>
> commit: 0dba1314d4f81115dce711292ec7981d17231064 ("scsi, block: fix duplicate bdi name registration crashes")
> https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-4.11/next
>
> in testcase: boot
>
> on test machine: qemu-system-i386 -enable-kvm -cpu Haswell,+smep,+smap -m 360M
>
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>
>
> +----------------------------------------------+------------+------------+
> | | efa7c9f97e | 0dba1314d4 |
> +----------------------------------------------+------------+------------+
> | boot_successes | 0 | 0 |
> | boot_failures | 6 | 6 |
> | WARNING:at_include/linux/kref.h:#kobject_get | 6 | 6 |
> | BUG:workqueue_lockup-pool | 2 | |
> | WARNING:at_fs/sysfs/dir.c:#sysfs_warn_dup | 0 | 6 |
> +----------------------------------------------+------------+------------+
>
>
>
> [ 8.820258] ------------[ cut here ]------------
> [ 8.821188] WARNING: CPU: 0 PID: 1 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x58/0x70
> [ 8.822994] sysfs: cannot create duplicate filename '/class/scsi_disk/0:0:0:0'
> [ 8.824567] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 4.10.0-rc5-00097-g0dba131 #1
> [ 8.826275] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
> [ 8.828156] Call Trace:
> [ 8.828851] dump_stack+0x79/0xa4
> [ 8.829628] __warn+0xd2/0xf0
> [ 8.830372] ? sysfs_warn_dup+0x58/0x70
> [ 8.831211] warn_slowpath_fmt+0x36/0x40
> [ 8.832054] sysfs_warn_dup+0x58/0x70
> [ 8.832865] sysfs_do_create_link_sd+0x9e/0xb0
> [ 8.833844] sysfs_create_link+0x20/0x40
> [ 8.834714] device_add+0x218/0x610
> [ 8.835511] ? kvasprintf_const+0x49/0x60
> [ 8.836352] ? kobject_set_name_vargs+0x62/0x80
> [ 8.837253] sd_probe+0x31a/0x390
> [ 8.838027] ? _raw_spin_unlock+0x1d/0x30
> [ 8.838884] driver_probe_device+0x190/0x4a0
> [ 8.839751] __device_attach_driver+0x6f/0x100
> [ 8.840736] ? klist_next+0x6e/0x100
> [ 8.841538] ? __driver_attach+0xf0/0xf0
> [ 8.842383] bus_for_each_drv+0x47/0x80
> [ 8.843226] __device_attach+0xa8/0x120
> [ 8.844062] ? __driver_attach+0xf0/0xf0
> [ 8.844902] device_initial_probe+0xd/0x10
> [ 8.845754] bus_probe_device+0x77/0x80
> [ 8.846593] device_add+0x320/0x610
> [ 8.847387] scsi_sysfs_add_sdev+0x85/0x2b0
> [ 8.848246] ? scsi_attach_vpd+0x1f9/0x210
> [ 8.849103] scsi_probe_and_add_lun+0xd44/0xe70
> [ 8.850021] __scsi_scan_target+0xd8/0x690
> [ 8.850918] ? __pm_runtime_resume+0x37/0x80
> [ 8.852124] scsi_scan_channel+0x8f/0xb0
> [ 8.852977] scsi_scan_host_selected+0x100/0x180
> [ 8.853885] do_scsi_scan_host+0x8a/0x90
> [ 8.854733] scsi_scan_host+0x15a/0x1a0
> [ 8.855562] sdebug_driver_probe+0x14f/0x3d0
> [ 8.856435] ? _raw_spin_unlock+0x1d/0x30
> [ 8.857270] ? devices_kset_move_last+0x71/0xc0
> [ 8.858170] ? sysfs_create_link+0x20/0x40
> [ 8.859057] driver_probe_device+0xd4/0x4a0
> [ 8.859924] __device_attach_driver+0x6f/0x100
> [ 8.860814] ? klist_next+0x6e/0x100
> [ 8.861619] ? __driver_attach+0xf0/0xf0
> [ 8.862470] bus_for_each_drv+0x47/0x80
> [ 8.863298] __device_attach+0xa8/0x120
> [ 8.864131] ? __driver_attach+0xf0/0xf0
> [ 8.864975] device_initial_probe+0xd/0x10
> [ 8.865831] bus_probe_device+0x77/0x80
> [ 8.866704] device_add+0x320/0x610
> [ 8.867497] ? pm_runtime_init+0xea/0xf0
> [ 8.868326] device_register+0x12/0x20
> [ 8.869146] sdebug_add_adapter+0xda/0x1e0
> [ 8.870002] ? driver_register+0x83/0xe0
> [ 8.870847] scsi_debug_init+0x5a0/0x6eb
> [ 8.871686] ? kobject_uevent+0xa/0x10
> [ 8.872507] ? driver_register+0x83/0xe0
> [ 8.873336] ? scsi_register_driver+0xf/0x20
> [ 8.874218] ? init_ch_module+0x9d/0x9d
> [ 8.875088] do_one_initcall+0x7b/0x132
> [ 8.875918] ? kernel_init_freeable+0xe7/0x188
> [ 8.876807] kernel_init_freeable+0x10a/0x188
> [ 8.877690] ? rest_init+0xb0/0xb0
> [ 8.878482] kernel_init+0xb/0x100
> [ 8.879262] ? schedule_tail+0xc/0x70
> [ 8.880076] ? rest_init+0xb0/0xb0
> [ 8.880861] ret_from_fork+0x21/0x2c
> [ 8.881688] ---[ end trace 62a20110376b9cdf ]---
>
>
> To reproduce:
>
> git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git
> cd lkp-tests
> bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email

These reproduction steps don't work for me. I also notice that 0day
is picking up on a later error, the real error is that we register to
scsi devices with the same name:

Dan Williams

unread,
Feb 4, 2017, 3:40:04 PM2/4/17
to
...hit send without the log showing two "0:0:0:0" devices being
registered at the same time.


[ 7.872969] scsi 0:0:0:0: Direct-Access Linux scsi_debug
0186 PQ: 0 ANSI: 7
[ 7.905516] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39
MB/8.00 MiB)
[ 7.935502] sd 0:0:0:0: [sda] Write Protect is off
[ 7.936460] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 7.975491] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, supports DPO and FUA
[ 8.395505] sd 0:0:0:0: [sda] Attached SCSI disk
[ 8.397174] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 8.398364] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 8.435526] sd 0:0:0:0: [sdb] 16384 512-byte logical blocks: (8.39
MB/8.00 MiB)
[ 8.455497] sd 0:0:0:0: [sdb] Write Protect is off
[ 8.456461] sd 0:0:0:0: [sdb] Mode Sense: 73 00 10 08
[ 8.495492] sd 0:0:0:0: [sdb] Write cache: enabled, read cache:
enabled, supports DPO and FUA
[ 8.555658] kobject (c9cad6a4): tried to init an initialized
object, something is seriously wrong.
[ 8.557439] CPU: 0 PID: 102 Comm: kworker/u2:1 Not tainted
4.10.0-rc5-00097-g0dba131 #1
[ 8.559082] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
[ 8.560960] Workqueue: events_unbound async_run_entry_fn
[ 8.561946] Call Trace:
[ 8.562635] dump_stack+0x79/0xa4
[ 8.563411] kobject_init+0x75/0x90
[ 8.564202] blk_mq_register_dev+0x2a/0x120
[ 8.565076] blk_register_queue+0x7b/0x130
[ 8.565939] device_add_disk+0x1e3/0x480
[ 8.566783] sd_probe_async+0xf1/0x1c0
[ 8.567597] ? __lock_acquire+0x43b/0x940
[ 8.568508] async_run_entry_fn+0x30/0x190
[ 8.569356] ? process_one_work+0x12f/0x430
[ 8.570220] process_one_work+0x1aa/0x430
[ 8.571068] ? process_one_work+0x12f/0x430
[ 8.571933] worker_thread+0x1dd/0x470
[ 8.572755] kthread+0xd4/0x100
[ 8.573509] ? process_one_work+0x430/0x430
[ 8.574373] ? __kthread_create_on_node+0x180/0x180
[ 8.575305] ret_from_fork+0x21/0x2c

James Bottomley

unread,
Feb 4, 2017, 4:10:05 PM2/4/17
to
OK, but just trying to shoot the messenger isn't at all helpful in this
case. We use the 0day test suite as one of our primary bulwarks
against submission bugs and it clearly identified your commit as the
first bad one. Thus either we need your code fixed or we need the test
fixed; can you work with the 0day people to root cause this? Jan can
probably help, just in case it's a patch interaction problem.

Thanks,

James

Dan Williams

unread,
Feb 4, 2017, 4:10:05 PM2/4/17
to
RIght, I'm not shooting the messenger just pointing out that the real
error occurs a few lines up in the log and it took me a while to
notice.

Back to wrestling with the reproduction instructions...

Christoph Hellwig

unread,
Feb 5, 2017, 4:20:05 AM2/5/17
to
Dan,

can you please quote your emails? I can't find any content inbetween
all these quotes.

Dan Williams

unread,
Feb 6, 2017, 12:20:06 AM2/6/17
to
Sorry, I'm using gmail, but I'll switch to attaching the logs.

So with help from Xiaolong I was able to reproduce this, and it does
not appear to be a regression. We simply change the failure output of
an existing bug. Attached is a log of the same test on v4.10-rc7 (i.e.
without the recent block/scsi fixes), and it shows sda being
registered twice.

"[ 6.647077] kobject (d5078ca4): tried to init an initialized
object, something is seriously wrong."

The change that "scsi, block: fix duplicate bdi name registration
crashes" makes is to properly try to register sdb since the sda devt
is still alive. However that's not a fix because we've managed to call
blk_register_queue() twice on the same queue.
4.10-rc7.log

James Bottomley

unread,
Feb 6, 2017, 7:20:07 PM2/6/17
to
OK, time to involve others: linux-scsi and linux-block cc'd and I've
inserted the log below.

James

---

[ 5.969672] scsi host0: scsi_debug: version 1.86 [20160430]
[ 5.969672] dev_size_mb=8, opts=0x0, submit_queues=1, statistics=0
[ 5.971895] scsi 0:0:0:0: Direct-Access Linux scsi_debug 0186 PQ: 0 ANSI: 7
[ 6.006983] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.026965] sd 0:0:0:0: [sda] Write Protect is off
[ 6.027870] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.066962] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.486962] sd 0:0:0:0: [sda] Attached SCSI disk
[ 6.488377] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 6.489455] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 6.526982] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.546964] sd 0:0:0:0: [sda] Write Protect is off
[ 6.547873] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.586963] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.647077] kobject (d5078ca4): tried to init an initialized object, something is seriously wrong.
[ 6.648723] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.649811] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.651418] Workqueue: events_unbound async_run_entry_fn
[ 6.652347] Call Trace:
[ 6.652987] dump_stack+0x79/0xa4
[ 6.653716] kobject_init+0x75/0x90
[ 6.654452] blk_mq_register_dev+0x2a/0x110
[ 6.655269] blk_register_queue+0x7b/0x130
[ 6.656080] device_add_disk+0x1c6/0x460
[ 6.656866] sd_probe_async+0xf1/0x1c0
[ 6.657634] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.658501] async_run_entry_fn+0x30/0x190
[ 6.659311] ? process_one_work+0x12f/0x430
[ 6.660113] process_one_work+0x1aa/0x430
[ 6.660901] ? process_one_work+0x12f/0x430
[ 6.661716] worker_thread+0x1dd/0x470
[ 6.662479] kthread+0xd4/0x100
[ 6.663175] ? process_one_work+0x430/0x430
[ 6.663984] ? __kthread_create_on_node+0x180/0x180
[ 6.664869] ret_from_fork+0x21/0x2c
[ 6.665638] kobject (ffab51ec): tried to init an initialized object, something is seriously wrong.
[ 6.667290] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.668372] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.669984] Workqueue: events_unbound async_run_entry_fn
[ 6.670909] Call Trace:
[ 6.671540] dump_stack+0x79/0xa4
[ 6.672266] kobject_init+0x75/0x90
[ 6.673011] blk_mq_register_dev+0x4c/0x110
[ 6.673832] blk_register_queue+0x7b/0x130
[ 6.674633] device_add_disk+0x1c6/0x460
[ 6.675413] sd_probe_async+0xf1/0x1c0
[ 6.676191] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.677057] async_run_entry_fn+0x30/0x190
[ 6.677860] ? process_one_work+0x12f/0x430
[ 6.678667] process_one_work+0x1aa/0x430
[ 6.679455] ? process_one_work+0x12f/0x430
[ 6.680269] worker_thread+0x1dd/0x470
[ 6.681036] kthread+0xd4/0x100
[ 6.681737] ? process_one_work+0x430/0x430
[ 6.682540] ? __kthread_create_on_node+0x180/0x180
[ 6.683420] ret_from_fork+0x21/0x2c
[ 6.684207] ------------[ cut here ]------------
[ 6.685067] WARNING: CPU: 0 PID: 99 at ./include/linux/kref.h:46 kobject_get+0x7f/0x90
[ 6.686592] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.687680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.689280] Workqueue: events_unbound async_run_entry_fn
[ 6.690208] Call Trace:
[ 6.690843] dump_stack+0x79/0xa4
[ 6.691563] __warn+0xd2/0xf0
[ 6.692246] ? kobject_get+0x7f/0x90
[ 6.692992] warn_slowpath_null+0x25/0x30
[ 6.693787] kobject_get+0x7f/0x90
[ 6.694505] kobject_add_internal+0x2e/0x360
[ 6.695322] ? kfree_const+0x18/0x20
[ 6.696071] ? kobject_set_name_vargs+0x62/0x80
[ 6.696914] kobject_add+0x35/0x80
[ 6.697642] blk_mq_register_hctx+0x95/0xc0
[ 6.698447] blk_mq_register_dev+0xc9/0x110
[ 6.699255] blk_register_queue+0x7b/0x130
[ 6.700059] device_add_disk+0x1c6/0x460
[ 6.700849] sd_probe_async+0xf1/0x1c0
[ 6.701628] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.702484] async_run_entry_fn+0x30/0x190
[ 6.703284] ? process_one_work+0x12f/0x430
[ 6.704098] process_one_work+0x1aa/0x430
[ 6.704894] ? process_one_work+0x12f/0x430
[ 6.705704] worker_thread+0x1dd/0x470
[ 6.706488] kthread+0xd4/0x100
[ 6.707198] ? process_one_work+0x430/0x430
[ 6.708016] ? __kthread_create_on_node+0x180/0x180
[ 6.708909] ret_from_fork+0x21/0x2c
[ 6.709676] ---[ end trace 1a7726d7c3d3c8d0 ]---
[ 5.969672] scsi host0: scsi_debug: version 1.86 [20160430]
[ 5.969672] dev_size_mb=8, opts=0x0, submit_queues=1, statistics=0
[ 5.971895] scsi 0:0:0:0: Direct-Access Linux scsi_debug 0186 PQ: 0 ANSI: 7
[ 6.006983] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.026965] sd 0:0:0:0: [sda] Write Protect is off
[ 6.027870] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.066962] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.486962] sd 0:0:0:0: [sda] Attached SCSI disk
[ 6.488377] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 6.489455] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 6.526982] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.546964] sd 0:0:0:0: [sda] Write Protect is off
[ 6.547873] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.586963] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.647077] kobject (d5078ca4): tried to init an initialized object, something is seriously wrong.
[ 6.648723] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.649811] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.651418] Workqueue: events_unbound async_run_entry_fn
[ 6.652347] Call Trace:
[ 6.652987] dump_stack+0x79/0xa4
[ 6.653716] kobject_init+0x75/0x90
[ 6.654452] blk_mq_register_dev+0x2a/0x110
[ 6.655269] blk_register_queue+0x7b/0x130
[ 6.656080] device_add_disk+0x1c6/0x460
[ 6.656866] sd_probe_async+0xf1/0x1c0
[ 6.657634] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.658501] async_run_entry_fn+0x30/0x190
[ 6.659311] ? process_one_work+0x12f/0x430
[ 6.660113] process_one_work+0x1aa/0x430
[ 6.660901] ? process_one_work+0x12f/0x430
[ 6.661716] worker_thread+0x1dd/0x470
[ 6.662479] kthread+0xd4/0x100
[ 6.663175] ? process_one_work+0x430/0x430
[ 6.663984] ? __kthread_create_on_node+0x180/0x180
[ 6.664869] ret_from_fork+0x21/0x2c
[ 6.665638] kobject (ffab51ec): tried to init an initialized object, something is seriously wrong.
[ 6.667290] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.668372] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.669984] Workqueue: events_unbound async_run_entry_fn
[ 6.670909] Call Trace:
[ 6.671540] dump_stack+0x79/0xa4
[ 6.672266] kobject_init+0x75/0x90
[ 6.673011] blk_mq_register_dev+0x4c/0x110
[ 6.673832] blk_register_queue+0x7b/0x130
[ 6.674633] device_add_disk+0x1c6/0x460
[ 6.675413] sd_probe_async+0xf1/0x1c0
[ 6.676191] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.677057] async_run_entry_fn+0x30/0x190
[ 6.677860] ? process_one_work+0x12f/0x430
[ 6.678667] process_one_work+0x1aa/0x430
[ 6.679455] ? process_one_work+0x12f/0x430
[ 6.680269] worker_thread+0x1dd/0x470
[ 6.681036] kthread+0xd4/0x100
[ 6.681737] ? process_one_work+0x430/0x430
[ 6.682540] ? __kthread_create_on_node+0x180/0x180
[ 6.683420] ret_from_fork+0x21/0x2c
[ 6.684207] ------------[ cut here ]------------
[ 6.685067] WARNING: CPU: 0 PID: 99 at ./include/linux/kref.h:46 kobject_get+0x7f/0x90
[ 6.686592] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.687680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.689280] Workqueue: events_unbound async_run_entry_fn
[ 6.690208] Call Trace:
[ 6.690843] dump_stack+0x79/0xa4
[ 6.691563] __warn+0xd2/0xf0
[ 6.692246] ? kobject_get+0x7f/0x90
[ 6.692992] warn_slowpath_null+0x25/0x30
[ 6.693787] kobject_get+0x7f/0x90
[ 6.694505] kobject_add_internal+0x2e/0x360
[ 6.695322] ? kfree_const+0x18/0x20
[ 6.696071] ? kobject_set_name_vargs+0x62/0x80
[ 6.696914] kobject_add+0x35/0x80
[ 6.697642] blk_mq_register_hctx+0x95/0xc0
[ 6.698447] blk_mq_register_dev+0xc9/0x110
[ 6.699255] blk_register_queue+0x7b/0x130
[ 6.700059] device_add_disk+0x1c6/0x460
[ 6.700849] sd_probe_async+0xf1/0x1c0
[ 6.701628] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.702484] async_run_entry_fn+0x30/0x190
[ 6.703284] ? process_one_work+0x12f/0x430
[ 6.704098] process_one_work+0x1aa/0x430
[ 6.704894] ? process_one_work+0x12f/0x430
[ 6.705704] worker_thread+0x1dd/0x470
[ 6.706488] kthread+0xd4/0x100
[ 6.707198] ? process_one_work+0x430/0x430
[ 6.708016] ? __kthread_create_on_node+0x180/0x180
[ 6.708909] ret_from_fork+0x21/0x2c
[ 6.709676] ---[ end trace 1a7726d7c3d3c8d0 ]---
[ 5.969672] scsi host0: scsi_debug: version 1.86 [20160430]
[ 5.969672] dev_size_mb=8, opts=0x0, submit_queues=1, statistics=0
[ 5.971895] scsi 0:0:0:0: Direct-Access Linux scsi_debug 0186 PQ: 0 ANSI: 7
[ 6.006983] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.026965] sd 0:0:0:0: [sda] Write Protect is off
[ 6.027870] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.066962] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.486962] sd 0:0:0:0: [sda] Attached SCSI disk
[ 6.488377] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 6.489455] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 6.526982] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.546964] sd 0:0:0:0: [sda] Write Protect is off
[ 6.547873] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.586963] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.647077] kobject (d5078ca4): tried to init an initialized object, something is seriously wrong.
[ 6.648723] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.649811] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.651418] Workqueue: events_unbound async_run_entry_fn
[ 6.652347] Call Trace:
[ 6.652987] dump_stack+0x79/0xa4
[ 6.653716] kobject_init+0x75/0x90
[ 6.654452] blk_mq_register_dev+0x2a/0x110
[ 6.655269] blk_register_queue+0x7b/0x130
[ 6.656080] device_add_disk+0x1c6/0x460
[ 6.656866] sd_probe_async+0xf1/0x1c0
[ 6.657634] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.658501] async_run_entry_fn+0x30/0x190
[ 6.659311] ? process_one_work+0x12f/0x430
[ 6.660113] process_one_work+0x1aa/0x430
[ 6.660901] ? process_one_work+0x12f/0x430
[ 6.661716] worker_thread+0x1dd/0x470
[ 6.662479] kthread+0xd4/0x100
[ 6.663175] ? process_one_work+0x430/0x430
[ 6.663984] ? __kthread_create_on_node+0x180/0x180
[ 6.664869] ret_from_fork+0x21/0x2c
[ 6.665638] kobject (ffab51ec): tried to init an initialized object, something is seriously wrong.
[ 6.667290] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.668372] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.669984] Workqueue: events_unbound async_run_entry_fn
[ 6.670909] Call Trace:
[ 6.671540] dump_stack+0x79/0xa4
[ 6.672266] kobject_init+0x75/0x90
[ 6.673011] blk_mq_register_dev+0x4c/0x110
[ 6.673832] blk_register_queue+0x7b/0x130
[ 6.674633] device_add_disk+0x1c6/0x460
[ 6.675413] sd_probe_async+0xf1/0x1c0
[ 6.676191] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.677057] async_run_entry_fn+0x30/0x190
[ 6.677860] ? process_one_work+0x12f/0x430
[ 6.678667] process_one_work+0x1aa/0x430
[ 6.679455] ? process_one_work+0x12f/0x430
[ 6.680269] worker_thread+0x1dd/0x470
[ 6.681036] kthread+0xd4/0x100
[ 6.681737] ? process_one_work+0x430/0x430
[ 6.682540] ? __kthread_create_on_node+0x180/0x180
[ 6.683420] ret_from_fork+0x21/0x2c
[ 6.684207] ------------[ cut here ]------------
[ 6.685067] WARNING: CPU: 0 PID: 99 at ./include/linux/kref.h:46 kobject_get+0x7f/0x90
[ 6.686592] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.687680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.689280] Workqueue: events_unbound async_run_entry_fn
[ 6.690208] Call Trace:
[ 6.690843] dump_stack+0x79/0xa4
[ 6.691563] __warn+0xd2/0xf0
[ 6.692246] ? kobject_get+0x7f/0x90
[ 6.692992] warn_slowpath_null+0x25/0x30
[ 6.693787] kobject_get+0x7f/0x90
[ 6.694505] kobject_add_internal+0x2e/0x360
[ 6.695322] ? kfree_const+0x18/0x20
[ 6.696071] ? kobject_set_name_vargs+0x62/0x80
[ 6.696914] kobject_add+0x35/0x80
[ 6.697642] blk_mq_register_hctx+0x95/0xc0
[ 6.698447] blk_mq_register_dev+0xc9/0x110
[ 6.699255] blk_register_queue+0x7b/0x130
[ 6.700059] device_add_disk+0x1c6/0x460
[ 6.700849] sd_probe_async+0xf1/0x1c0
[ 6.701628] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.702484] async_run_entry_fn+0x30/0x190
[ 6.703284] ? process_one_work+0x12f/0x430
[ 6.704098] process_one_work+0x1aa/0x430
[ 6.704894] ? process_one_work+0x12f/0x430
[ 6.705704] worker_thread+0x1dd/0x470
[ 6.706488] kthread+0xd4/0x100
[ 6.707198] ? process_one_work+0x430/0x430
[ 6.708016] ? __kthread_create_on_node+0x180/0x180
[ 6.708909] ret_from_fork+0x21/0x2c
[ 6.709676] ---[ end trace 1a7726d7c3d3c8d0 ]---
[ 5.969672] scsi host0: scsi_debug: version 1.86 [20160430]
[ 5.969672] dev_size_mb=8, opts=0x0, submit_queues=1, statistics=0
[ 5.971895] scsi 0:0:0:0: Direct-Access Linux scsi_debug 0186 PQ: 0 ANSI: 7
[ 6.006983] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.026965] sd 0:0:0:0: [sda] Write Protect is off
[ 6.027870] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.066962] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.486962] sd 0:0:0:0: [sda] Attached SCSI disk
[ 6.488377] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 6.489455] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 6.526982] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.546964] sd 0:0:0:0: [sda] Write Protect is off
[ 6.547873] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.586963] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.647077] kobject (d5078ca4): tried to init an initialized object, something is seriously wrong.
[ 6.648723] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.649811] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.651418] Workqueue: events_unbound async_run_entry_fn
[ 6.652347] Call Trace:
[ 6.652987] dump_stack+0x79/0xa4
[ 6.653716] kobject_init+0x75/0x90
[ 6.654452] blk_mq_register_dev+0x2a/0x110
[ 6.655269] blk_register_queue+0x7b/0x130
[ 6.656080] device_add_disk+0x1c6/0x460
[ 6.656866] sd_probe_async+0xf1/0x1c0
[ 6.657634] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.658501] async_run_entry_fn+0x30/0x190
[ 6.659311] ? process_one_work+0x12f/0x430
[ 6.660113] process_one_work+0x1aa/0x430
[ 6.660901] ? process_one_work+0x12f/0x430
[ 6.661716] worker_thread+0x1dd/0x470
[ 6.662479] kthread+0xd4/0x100
[ 6.663175] ? process_one_work+0x430/0x430
[ 6.663984] ? __kthread_create_on_node+0x180/0x180
[ 6.664869] ret_from_fork+0x21/0x2c
[ 6.665638] kobject (ffab51ec): tried to init an initialized object, something is seriously wrong.
[ 6.667290] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.668372] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.669984] Workqueue: events_unbound async_run_entry_fn
[ 6.670909] Call Trace:
[ 6.671540] dump_stack+0x79/0xa4
[ 6.672266] kobject_init+0x75/0x90
[ 6.673011] blk_mq_register_dev+0x4c/0x110
[ 6.673832] blk_register_queue+0x7b/0x130
[ 6.674633] device_add_disk+0x1c6/0x460
[ 6.675413] sd_probe_async+0xf1/0x1c0
[ 6.676191] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.677057] async_run_entry_fn+0x30/0x190
[ 6.677860] ? process_one_work+0x12f/0x430
[ 6.678667] process_one_work+0x1aa/0x430
[ 6.679455] ? process_one_work+0x12f/0x430
[ 6.680269] worker_thread+0x1dd/0x470
[ 6.681036] kthread+0xd4/0x100
[ 6.681737] ? process_one_work+0x430/0x430
[ 6.682540] ? __kthread_create_on_node+0x180/0x180
[ 6.683420] ret_from_fork+0x21/0x2c
[ 6.684207] ------------[ cut here ]------------
[ 6.685067] WARNING: CPU: 0 PID: 99 at ./include/linux/kref.h:46 kobject_get+0x7f/0x90
[ 6.686592] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.687680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.689280] Workqueue: events_unbound async_run_entry_fn
[ 6.690208] Call Trace:
[ 6.690843] dump_stack+0x79/0xa4
[ 6.691563] __warn+0xd2/0xf0
[ 6.692246] ? kobject_get+0x7f/0x90
[ 6.692992] warn_slowpath_null+0x25/0x30
[ 6.693787] kobject_get+0x7f/0x90
[ 6.694505] kobject_add_internal+0x2e/0x360
[ 6.695322] ? kfree_const+0x18/0x20
[ 6.696071] ? kobject_set_name_vargs+0x62/0x80
[ 6.696914] kobject_add+0x35/0x80
[ 6.697642] blk_mq_register_hctx+0x95/0xc0
[ 6.698447] blk_mq_register_dev+0xc9/0x110
[ 6.699255] blk_register_queue+0x7b/0x130
[ 6.700059] device_add_disk+0x1c6/0x460
[ 6.700849] sd_probe_async+0xf1/0x1c0
[ 6.701628] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.702484] async_run_entry_fn+0x30/0x190
[ 6.703284] ? process_one_work+0x12f/0x430
[ 6.704098] process_one_work+0x1aa/0x430
[ 6.704894] ? process_one_work+0x12f/0x430
[ 6.705704] worker_thread+0x1dd/0x470
[ 6.706488] kthread+0xd4/0x100
[ 6.707198] ? process_one_work+0x430/0x430
[ 6.708016] ? __kthread_create_on_node+0x180/0x180
[ 6.708909] ret_from_fork+0x21/0x2c
[ 6.709676] ---[ end trace 1a7726d7c3d3c8d0 ]---
[ 5.969672] scsi host0: scsi_debug: version 1.86 [20160430]
[ 5.969672] dev_size_mb=8, opts=0x0, submit_queues=1, statistics=0
[ 5.971895] scsi 0:0:0:0: Direct-Access Linux scsi_debug 0186 PQ: 0 ANSI: 7
[ 6.006983] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.026965] sd 0:0:0:0: [sda] Write Protect is off
[ 6.027870] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.066962] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.486962] sd 0:0:0:0: [sda] Attached SCSI disk
[ 6.488377] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 6.489455] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 6.526982] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.546964] sd 0:0:0:0: [sda] Write Protect is off
[ 6.547873] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.586963] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.647077] kobject (d5078ca4): tried to init an initialized object, something is seriously wrong.
[ 6.648723] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.649811] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.651418] Workqueue: events_unbound async_run_entry_fn
[ 6.652347] Call Trace:
[ 6.652987] dump_stack+0x79/0xa4
[ 6.653716] kobject_init+0x75/0x90
[ 6.654452] blk_mq_register_dev+0x2a/0x110
[ 6.655269] blk_register_queue+0x7b/0x130
[ 6.656080] device_add_disk+0x1c6/0x460
[ 6.656866] sd_probe_async+0xf1/0x1c0
[ 6.657634] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.658501] async_run_entry_fn+0x30/0x190
[ 6.659311] ? process_one_work+0x12f/0x430
[ 6.660113] process_one_work+0x1aa/0x430
[ 6.660901] ? process_one_work+0x12f/0x430
[ 6.661716] worker_thread+0x1dd/0x470
[ 6.662479] kthread+0xd4/0x100
[ 6.663175] ? process_one_work+0x430/0x430
[ 6.663984] ? __kthread_create_on_node+0x180/0x180
[ 6.664869] ret_from_fork+0x21/0x2c
[ 6.665638] kobject (ffab51ec): tried to init an initialized object, something is seriously wrong.
[ 6.667290] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.668372] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.669984] Workqueue: events_unbound async_run_entry_fn
[ 6.670909] Call Trace:
[ 6.671540] dump_stack+0x79/0xa4
[ 6.672266] kobject_init+0x75/0x90
[ 6.673011] blk_mq_register_dev+0x4c/0x110
[ 6.673832] blk_register_queue+0x7b/0x130
[ 6.674633] device_add_disk+0x1c6/0x460
[ 6.675413] sd_probe_async+0xf1/0x1c0
[ 6.676191] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.677057] async_run_entry_fn+0x30/0x190
[ 6.677860] ? process_one_work+0x12f/0x430
[ 6.678667] process_one_work+0x1aa/0x430
[ 6.679455] ? process_one_work+0x12f/0x430
[ 6.680269] worker_thread+0x1dd/0x470
[ 6.681036] kthread+0xd4/0x100
[ 6.681737] ? process_one_work+0x430/0x430
[ 6.682540] ? __kthread_create_on_node+0x180/0x180
[ 6.683420] ret_from_fork+0x21/0x2c
[ 6.684207] ------------[ cut here ]------------
[ 6.685067] WARNING: CPU: 0 PID: 99 at ./include/linux/kref.h:46 kobject_get+0x7f/0x90
[ 6.686592] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.687680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.689280] Workqueue: events_unbound async_run_entry_fn
[ 6.690208] Call Trace:
[ 6.690843] dump_stack+0x79/0xa4
[ 6.691563] __warn+0xd2/0xf0
[ 6.692246] ? kobject_get+0x7f/0x90
[ 6.692992] warn_slowpath_null+0x25/0x30
[ 6.693787] kobject_get+0x7f/0x90
[ 6.694505] kobject_add_internal+0x2e/0x360
[ 6.695322] ? kfree_const+0x18/0x20
[ 6.696071] ? kobject_set_name_vargs+0x62/0x80
[ 6.696914] kobject_add+0x35/0x80
[ 6.697642] blk_mq_register_hctx+0x95/0xc0
[ 6.698447] blk_mq_register_dev+0xc9/0x110
[ 6.699255] blk_register_queue+0x7b/0x130
[ 6.700059] device_add_disk+0x1c6/0x460
[ 6.700849] sd_probe_async+0xf1/0x1c0
[ 6.701628] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.702484] async_run_entry_fn+0x30/0x190
[ 6.703284] ? process_one_work+0x12f/0x430
[ 6.704098] process_one_work+0x1aa/0x430
[ 6.704894] ? process_one_work+0x12f/0x430
[ 6.705704] worker_thread+0x1dd/0x470
[ 6.706488] kthread+0xd4/0x100
[ 6.707198] ? process_one_work+0x430/0x430
[ 6.708016] ? __kthread_create_on_node+0x180/0x180
[ 6.708909] ret_from_fork+0x21/0x2c
[ 6.709676] ---[ end trace 1a7726d7c3d3c8d0 ]---
csi host0: scsi_debug: version 1.86 [20160430]
[ 5.969672] dev_size_mb=8, opts=0x0, submit_queues=1, statistics=0
[ 5.971895] scsi 0:0:0:0: Direct-Access Linux scsi_debug 0186 PQ: 0 ANSI: 7
[ 6.006983] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.026965] sd 0:0:0:0: [sda] Write Protect is off
[ 6.027870] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.066962] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.486962] sd 0:0:0:0: [sda] Attached SCSI disk
[ 6.488377] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 6.489455] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 6.526982] sd 0:0:0:0: [sda] 16384 512-byte logical blocks: (8.39 MB/8.00 MiB)
[ 6.546964] sd 0:0:0:0: [sda] Write Protect is off
[ 6.547873] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 6.586963] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 6.647077] kobject (d5078ca4): tried to init an initialized object, something is seriously wrong.
[ 6.648723] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.649811] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.651418] Workqueue: events_unbound async_run_entry_fn
[ 6.652347] Call Trace:
[ 6.652987] dump_stack+0x79/0xa4
[ 6.653716] kobject_init+0x75/0x90
[ 6.654452] blk_mq_register_dev+0x2a/0x110
[ 6.655269] blk_register_queue+0x7b/0x130
[ 6.656080] device_add_disk+0x1c6/0x460
[ 6.656866] sd_probe_async+0xf1/0x1c0
[ 6.657634] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.658501] async_run_entry_fn+0x30/0x190
[ 6.659311] ? process_one_work+0x12f/0x430
[ 6.660113] process_one_work+0x1aa/0x430
[ 6.660901] ? process_one_work+0x12f/0x430
[ 6.661716] worker_thread+0x1dd/0x470
[ 6.662479] kthread+0xd4/0x100
[ 6.663175] ? process_one_work+0x430/0x430
[ 6.663984] ? __kthread_create_on_node+0x180/0x180
[ 6.664869] ret_from_fork+0x21/0x2c
[ 6.665638] kobject (ffab51ec): tried to init an initialized object, something is seriously wrong.
[ 6.667290] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.668372] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.669984] Workqueue: events_unbound async_run_entry_fn
[ 6.670909] Call Trace:
[ 6.671540] dump_stack+0x79/0xa4
[ 6.672266] kobject_init+0x75/0x90
[ 6.673011] blk_mq_register_dev+0x4c/0x110
[ 6.673832] blk_register_queue+0x7b/0x130
[ 6.674633] device_add_disk+0x1c6/0x460
[ 6.675413] sd_probe_async+0xf1/0x1c0
[ 6.676191] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.677057] async_run_entry_fn+0x30/0x190
[ 6.677860] ? process_one_work+0x12f/0x430
[ 6.678667] process_one_work+0x1aa/0x430
[ 6.679455] ? process_one_work+0x12f/0x430
[ 6.680269] worker_thread+0x1dd/0x470
[ 6.681036] kthread+0xd4/0x100
[ 6.681737] ? process_one_work+0x430/0x430
[ 6.682540] ? __kthread_create_on_node+0x180/0x180
[ 6.683420] ret_from_fork+0x21/0x2c
[ 6.684207] ------------[ cut here ]------------
[ 6.685067] WARNING: CPU: 0 PID: 99 at ./include/linux/kref.h:46 kobject_get+0x7f/0x90
[ 6.686592] CPU: 0 PID: 99 Comm: kworker/u2:1 Not tainted 4.10.0-rc7 #932
[ 6.687680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
[ 6.689280] Workqueue: events_unbound async_run_entry_fn
[ 6.690208] Call Trace:
[ 6.690843] dump_stack+0x79/0xa4
[ 6.691563] __warn+0xd2/0xf0
[ 6.692246] ? kobject_get+0x7f/0x90
[ 6.692992] warn_slowpath_null+0x25/0x30
[ 6.693787] kobject_get+0x7f/0x90
[ 6.694505] kobject_add_internal+0x2e/0x360
[ 6.695322] ? kfree_const+0x18/0x20
[ 6.696071] ? kobject_set_name_vargs+0x62/0x80
[ 6.696914] kobject_add+0x35/0x80
[ 6.697642] blk_mq_register_hctx+0x95/0xc0
[ 6.698447] blk_mq_register_dev+0xc9/0x110
[ 6.699255] blk_register_queue+0x7b/0x130
[ 6.700059] device_add_disk+0x1c6/0x460
[ 6.700849] sd_probe_async+0xf1/0x1c0
[ 6.701628] ? __lock_acquire.isra.14+0x43b/0x940
[ 6.702484] async_run_entry_fn+0x30/0x190
[ 6.703284] ? process_one_work+0x12f/0x430
[ 6.704098] process_one_work+0x1aa/0x430
[ 6.704894] ? process_one_work+0x12f/0x430
[ 6.705704] worker_thread+0x1dd/0x470
[ 6.706488] kthread+0xd4/0x100
[ 6.707198] ? process_one_work+0x430/0x430
[ 6.708016] ? __kthread_create_on_node+0x180/0x180
[ 6.708909] ret_from_fork+0x21/0x2c
[ 6.709676] ---[ end trace 1a7726d7c3d3c8d0 ]---

Dan Williams

unread,
Feb 7, 2017, 12:50:04 AM2/7/17
to
On Mon, Feb 6, 2017 at 8:09 PM, Jens Axboe <ax...@fb.com> wrote:
> So sda is probed twice, and hilarity ensues when we try to register it
> twice. I can't reproduce this, using scsi_debug and with scsi_async
> enabled.
>
> This is running linux-next? What's your .config?
>

The original failure report is here:

http://marc.info/?l=linux-kernel&m=148619222300774&w=2

...but it reproduces on current mainline with the same config. I
haven't spotted what makes scsi_debug behave like this.

James Bottomley

unread,
Feb 8, 2017, 7:10:05 PM2/8/17
to
Looking at the config, it's a static debug with report luns enabled.
Is it as simple as the fact that we probe lun 0 manually to see if the
target exists, but then we don't account for the fact that we already
did this, so if it turns up again in the report lun scan, we'll probe
it again leading to a double add. If that theory is correct, this may
be the fix (compile tested only).

James

---

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 6f7128f..ba4be08 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1441,6 +1441,10 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
for (lunp = &lun_data[1]; lunp <= &lun_data[num_luns]; lunp++) {
lun = scsilun_to_int(lunp);

+ if (lun == 0)
+ /* already scanned LUN 0 */
+ continue;
+
if (lun > sdev->host->max_lun) {
sdev_printk(KERN_WARNING, sdev,
"lun%llu has a LUN larger than"

James Bottomley

unread,
Feb 11, 2017, 11:10:09 AM2/11/17
to
On Mon, 2017-02-06 at 21:09 -0700, Jens Axboe wrote:
> On 02/06/2017 05:14 PM, James Bottomley wrote:
> So sda is probed twice, and hilarity ensues when we try to register
> it twice. I can't reproduce this, using scsi_debug and with
> scsi_async enabled.

Actually, when you look closely, it's not a double add; it's an
add/remove/add. You can see this from

[ 6.488377] sd 0:0:0:0: [sda] Synchronizing SCSI cache

That's from sd_shutdown() as the driver is removing. It looks like
something with the config caused the built in SCSI debug to do this
(not sure why), but since the stack trace is in block, I think the bug
is in the remove path: something didn't release the mq object
correctly.

James
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