2016-04-11 09:00:24

by Sergey Senozhatsky

[permalink] [raw]
Subject: [-next] BUG_ON in scsi_target_destroy()

Hello,

commit 7b106f2de6938c31ce5e9c86bc70ad3904666b96
Author: Johannes Thumshirn <[email protected]>
Date: Tue Apr 5 11:50:44 2016 +0200

scsi: Add intermediate STARGET_REMOVE state to scsi_target_state


BUG_ON()s (next-20160411) each time I remove a usb flash

[ 49.561600] [<ffffffffa0087f42>] scsi_target_destroy+0x5a/0xcb [scsi_mod]
[ 49.561607] [<ffffffffa0089099>] scsi_target_reap+0x4a/0x4f [scsi_mod]
[ 49.561613] [<ffffffffa008b453>] __scsi_remove_device+0xc3/0xd0 [scsi_mod]
[ 49.561619] [<ffffffffa0089d7b>] scsi_forget_host+0x52/0x63 [scsi_mod]
[ 49.561623] [<ffffffffa0080dbc>] scsi_remove_host+0x8c/0x102 [scsi_mod]
[ 49.561627] [<ffffffffa015c447>] usb_stor_disconnect+0x6b/0xab [usb_storage]
[ 49.561634] [<ffffffffa0013f73>] usb_unbind_interface+0x77/0x1ca [usbcore]
[ 49.561636] [<ffffffff813ae064>] __device_release_driver+0x9d/0x121
[ 49.561638] [<ffffffff813ae10b>] device_release_driver+0x23/0x30
[ 49.561639] [<ffffffff813ad2d1>] bus_remove_device+0xfb/0x10e
[ 49.561641] [<ffffffff813aac05>] device_del+0x164/0x1e6
[ 49.561648] [<ffffffffa0011b09>] ? remove_intf_ep_devs+0x3b/0x48 [usbcore]
[ 49.561655] [<ffffffffa001200e>] usb_disable_device+0x84/0x1a5 [usbcore]
[ 49.561661] [<ffffffffa000ac7b>] usb_disconnect+0x94/0x19f [usbcore]
[ 49.561667] [<ffffffffa000c2ab>] hub_event+0x5c1/0xdea [usbcore]
[ 49.561670] [<ffffffff810530b1>] process_one_work+0x1dc/0x37f
[ 49.561672] [<ffffffff81053dc5>] worker_thread+0x282/0x36d
[ 49.561673] [<ffffffff81053b43>] ? rescuer_thread+0x2ae/0x2ae
[ 49.561675] [<ffffffff810580a8>] kthread+0xd2/0xda
[ 49.561678] [<ffffffff814bbf92>] ret_from_fork+0x22/0x40
[ 49.561679] [<ffffffff81057fd6>] ? kthread_worker_fn+0x13e/0x13e

-ss


2016-04-13 08:41:57

by Johannes Thumshirn

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

Hi Sergey, Xiong,

Can you try below patch?

On Montag, 11. April 2016 18:01:47 CEST Sergey Senozhatsky wrote:
> Hello,
>
> commit 7b106f2de6938c31ce5e9c86bc70ad3904666b96
> Author: Johannes Thumshirn <[email protected]>
> Date: Tue Apr 5 11:50:44 2016 +0200
>
> scsi: Add intermediate STARGET_REMOVE state to scsi_target_state
>
>
> BUG_ON()s (next-20160411) each time I remove a usb flash
>
> [ 49.561600] [<ffffffffa0087f42>] scsi_target_destroy+0x5a/0xcb [scsi_mod]
> [ 49.561607] [<ffffffffa0089099>] scsi_target_reap+0x4a/0x4f [scsi_mod]
> [ 49.561613] [<ffffffffa008b453>] __scsi_remove_device+0xc3/0xd0 [scsi_mod]
> [ 49.561619] [<ffffffffa0089d7b>] scsi_forget_host+0x52/0x63 [scsi_mod]
> [ 49.561623] [<ffffffffa0080dbc>] scsi_remove_host+0x8c/0x102 [scsi_mod]
> [ 49.561627] [<ffffffffa015c447>] usb_stor_disconnect+0x6b/0xab [usb_storage]
> [ 49.561634] [<ffffffffa0013f73>] usb_unbind_interface+0x77/0x1ca [usbcore]
> [ 49.561636] [<ffffffff813ae064>] __device_release_driver+0x9d/0x121
> [ 49.561638] [<ffffffff813ae10b>] device_release_driver+0x23/0x30
> [ 49.561639] [<ffffffff813ad2d1>] bus_remove_device+0xfb/0x10e
> [ 49.561641] [<ffffffff813aac05>] device_del+0x164/0x1e6
> [ 49.561648] [<ffffffffa0011b09>] ? remove_intf_ep_devs+0x3b/0x48 [usbcore]
> [ 49.561655] [<ffffffffa001200e>] usb_disable_device+0x84/0x1a5 [usbcore]
> [ 49.561661] [<ffffffffa000ac7b>] usb_disconnect+0x94/0x19f [usbcore]
> [ 49.561667] [<ffffffffa000c2ab>] hub_event+0x5c1/0xdea [usbcore]
> [ 49.561670] [<ffffffff810530b1>] process_one_work+0x1dc/0x37f
> [ 49.561672] [<ffffffff81053dc5>] worker_thread+0x282/0x36d
> [ 49.561673] [<ffffffff81053b43>] ? rescuer_thread+0x2ae/0x2ae
> [ 49.561675] [<ffffffff810580a8>] kthread+0xd2/0xda
> [ 49.561678] [<ffffffff814bbf92>] ret_from_fork+0x22/0x40
> [ 49.561679] [<ffffffff81057fd6>] ? kthread_worker_fn+0x13e/0x13e
>
> -ss
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 0734927..0c00928 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1276,6 +1276,7 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
void __scsi_remove_device(struct scsi_device *sdev)
{
struct device *dev = &sdev->sdev_gendev;
+ struct scsi_target *starget;

/*
* This cleanup path is not reentrant and while it is impossible
@@ -1315,7 +1316,9 @@ void __scsi_remove_device(struct scsi_device *sdev)
* remoed sysfs visibility from the device, so make the target
* invisible if this was the last device underneath it.
*/
- scsi_target_reap(scsi_target(sdev));
+ starget = scsi_target(sdev);
+ starget->state = STARGET_REMOVE;
+ scsi_target_reap(starget);

put_device(dev);
}



--
Johannes Thumshirn Storage
[email protected] +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: Felix Imend?rffer, Jane Smithard, Graham Norton
HRB 21284 (AG N?rnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

2016-04-13 13:49:25

by Sergey Senozhatsky

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

Hi,

On (04/13/16 10:41), Johannes Thumshirn wrote:
> Hi Sergey, Xiong,
>
> Can you try below patch?

it panics my system.
first it warn_on-s in lib/kobject.c:244

then NULL dereferences
do_scan_async
__scsi_remove_device
scsi_target_reap
device_del
dpm_sysfs_remove
sysfs_unmerge_group
kernfs_find_and_get_ns
kernfs_find_ns

-ss

2016-04-13 14:00:00

by Johannes Thumshirn

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

On Mittwoch, 13. April 2016 23:47:04 CEST Sergey Senozhatsky wrote:
> Hi,
>
> On (04/13/16 10:41), Johannes Thumshirn wrote:
> > Hi Sergey, Xiong,
> >
> > Can you try below patch?
>
> it panics my system.
> first it warn_on-s in lib/kobject.c:244
>
> then NULL dereferences
> do_scan_async
> __scsi_remove_device
> scsi_target_reap
> device_del
> dpm_sysfs_remove
> sysfs_unmerge_group
> kernfs_find_and_get_ns
> kernfs_find_ns
>
> -ss
>

Thanks for the update, I'll have a look into the callchain

--
Johannes Thumshirn Storage
[email protected] +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: Felix Imend?rffer, Jane Smithard, Graham Norton
HRB 21284 (AG N?rnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

2016-04-13 15:14:53

by James Bottomley

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

On Wed, 2016-04-13 at 10:41 +0200, Johannes Thumshirn wrote:
> Hi Sergey, Xiong,
>
> Can you try below patch?
>
> On Montag, 11. April 2016 18:01:47 CEST Sergey Senozhatsky wrote:
> > Hello,
> >
> > commit 7b106f2de6938c31ce5e9c86bc70ad3904666b96
> > Author: Johannes Thumshirn <[email protected]>
> > Date: Tue Apr 5 11:50:44 2016 +0200
> >
> > scsi: Add intermediate STARGET_REMOVE state to
> > scsi_target_state
> >
> >
> > BUG_ON()s (next-20160411) each time I remove a usb flash
> >
> > [ 49.561600] [<ffffffffa0087f42>] scsi_target_destroy+0x5a/0xcb
> > [scsi_mod]
> > [ 49.561607] [<ffffffffa0089099>] scsi_target_reap+0x4a/0x4f
> > [scsi_mod]
> > [ 49.561613] [<ffffffffa008b453>] __scsi_remove_device+0xc3/0xd0
> > [scsi_mod]
> > [ 49.561619] [<ffffffffa0089d7b>] scsi_forget_host+0x52/0x63
> > [scsi_mod]
> > [ 49.561623] [<ffffffffa0080dbc>] scsi_remove_host+0x8c/0x102
> > [scsi_mod]
> > [ 49.561627] [<ffffffffa015c447>] usb_stor_disconnect+0x6b/0xab
> > [usb_storage]
> > [ 49.561634] [<ffffffffa0013f73>]
> > usb_unbind_interface+0x77/0x1ca [usbcore]
> > [ 49.561636] [<ffffffff813ae064>]
> > __device_release_driver+0x9d/0x121
> > [ 49.561638] [<ffffffff813ae10b>]
> > device_release_driver+0x23/0x30
> > [ 49.561639] [<ffffffff813ad2d1>] bus_remove_device+0xfb/0x10e
> > [ 49.561641] [<ffffffff813aac05>] device_del+0x164/0x1e6
> > [ 49.561648] [<ffffffffa0011b09>] ?
> > remove_intf_ep_devs+0x3b/0x48 [usbcore]
> > [ 49.561655] [<ffffffffa001200e>] usb_disable_device+0x84/0x1a5
> > [usbcore]
> > [ 49.561661] [<ffffffffa000ac7b>] usb_disconnect+0x94/0x19f
> > [usbcore]
> > [ 49.561667] [<ffffffffa000c2ab>] hub_event+0x5c1/0xdea
> > [usbcore]
> > [ 49.561670] [<ffffffff810530b1>] process_one_work+0x1dc/0x37f
> > [ 49.561672] [<ffffffff81053dc5>] worker_thread+0x282/0x36d
> > [ 49.561673] [<ffffffff81053b43>] ? rescuer_thread+0x2ae/0x2ae
> > [ 49.561675] [<ffffffff810580a8>] kthread+0xd2/0xda
> > [ 49.561678] [<ffffffff814bbf92>] ret_from_fork+0x22/0x40
> > [ 49.561679] [<ffffffff81057fd6>] ?
> > kthread_worker_fn+0x13e/0x13e
> >
> > -ss
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux
> > -scsi" in
> > the body of a message to [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 0734927..0c00928 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1276,6 +1276,7 @@ int scsi_sysfs_add_sdev(struct scsi_device
> *sdev)
> void __scsi_remove_device(struct scsi_device *sdev)
> {
> struct device *dev = &sdev->sdev_gendev;
> + struct scsi_target *starget;
>
> /*
> * This cleanup path is not reentrant and while it is
> impossible
> @@ -1315,7 +1316,9 @@ void __scsi_remove_device(struct scsi_device
> *sdev)
> * remoed sysfs visibility from the device, so make the
> target
> * invisible if this was the last device underneath it.
> */
> - scsi_target_reap(scsi_target(sdev));
> + starget = scsi_target(sdev);
> + starget->state = STARGET_REMOVE;
> + scsi_target_reap(starget);

How about good grief no! A device with multiple targets will get it's
lists screwed with this

The STARGET_REMOVE state you added only applies to the case we're
trying to kill a target. In the natural operation case, which is what
everyone else is running into, we will try to remove a running target
when it has no more scsi devices left on it. So the correct patch
should be to make the BUG_ON see this:

James

---

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 27df7e7..e0a78f5 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -319,8 +319,7 @@ static void scsi_target_destroy(struct scsi_target *starget)
struct Scsi_Host *shost = dev_to_shost(dev->parent);
unsigned long flags;

- BUG_ON(starget->state != STARGET_REMOVE &&
- starget->state != STARGET_CREATED);
+ BUG_ON(starget->state == STARGET_DEL);
starget->state = STARGET_DEL;
transport_destroy_device(dev);
spin_lock_irqsave(shost->host_lock, flags);

2016-04-14 02:06:26

by Sergey Senozhatsky

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

Hello,

On (04/13/16 08:14), James Bottomley wrote:
[..]
> How about good grief no! A device with multiple targets will get it's
> lists screwed with this
>
> The STARGET_REMOVE state you added only applies to the case we're
> trying to kill a target. In the natural operation case, which is what
> everyone else is running into, we will try to remove a running target
> when it has no more scsi devices left on it. So the correct patch
> should be to make the BUG_ON see this:

works for me.
Reported-and-tested-by: Sergey Senozhatsky <[email protected]>

-ss

> James
>
> ---
>
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 27df7e7..e0a78f5 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -319,8 +319,7 @@ static void scsi_target_destroy(struct scsi_target *starget)
> struct Scsi_Host *shost = dev_to_shost(dev->parent);
> unsigned long flags;
>
> - BUG_ON(starget->state != STARGET_REMOVE &&
> - starget->state != STARGET_CREATED);
> + BUG_ON(starget->state == STARGET_DEL);
> starget->state = STARGET_DEL;
> transport_destroy_device(dev);
> spin_lock_irqsave(shost->host_lock, flags);
>

2016-04-15 04:31:27

by Murphy Zhou

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

Hi,

On Wed, Apr 13, 2016 at 4:41 PM, Johannes Thumshirn <[email protected]> wrote:
> Hi Sergey, Xiong,
>
> Can you try below patch?

This survives modprobe -r scsi_debug.

>
> On Montag, 11. April 2016 18:01:47 CEST Sergey Senozhatsky wrote:
>> Hello,
>>
>> commit 7b106f2de6938c31ce5e9c86bc70ad3904666b96
>> Author: Johannes Thumshirn <[email protected]>
>> Date: Tue Apr 5 11:50:44 2016 +0200
>>
>> scsi: Add intermediate STARGET_REMOVE state to scsi_target_state
>>
>>
>> BUG_ON()s (next-20160411) each time I remove a usb flash
>>
>> [ 49.561600] [<ffffffffa0087f42>] scsi_target_destroy+0x5a/0xcb [scsi_mod]
>> [ 49.561607] [<ffffffffa0089099>] scsi_target_reap+0x4a/0x4f [scsi_mod]
>> [ 49.561613] [<ffffffffa008b453>] __scsi_remove_device+0xc3/0xd0 [scsi_mod]
>> [ 49.561619] [<ffffffffa0089d7b>] scsi_forget_host+0x52/0x63 [scsi_mod]
>> [ 49.561623] [<ffffffffa0080dbc>] scsi_remove_host+0x8c/0x102 [scsi_mod]
>> [ 49.561627] [<ffffffffa015c447>] usb_stor_disconnect+0x6b/0xab [usb_storage]
>> [ 49.561634] [<ffffffffa0013f73>] usb_unbind_interface+0x77/0x1ca [usbcore]
>> [ 49.561636] [<ffffffff813ae064>] __device_release_driver+0x9d/0x121
>> [ 49.561638] [<ffffffff813ae10b>] device_release_driver+0x23/0x30
>> [ 49.561639] [<ffffffff813ad2d1>] bus_remove_device+0xfb/0x10e
>> [ 49.561641] [<ffffffff813aac05>] device_del+0x164/0x1e6
>> [ 49.561648] [<ffffffffa0011b09>] ? remove_intf_ep_devs+0x3b/0x48 [usbcore]
>> [ 49.561655] [<ffffffffa001200e>] usb_disable_device+0x84/0x1a5 [usbcore]
>> [ 49.561661] [<ffffffffa000ac7b>] usb_disconnect+0x94/0x19f [usbcore]
>> [ 49.561667] [<ffffffffa000c2ab>] hub_event+0x5c1/0xdea [usbcore]
>> [ 49.561670] [<ffffffff810530b1>] process_one_work+0x1dc/0x37f
>> [ 49.561672] [<ffffffff81053dc5>] worker_thread+0x282/0x36d
>> [ 49.561673] [<ffffffff81053b43>] ? rescuer_thread+0x2ae/0x2ae
>> [ 49.561675] [<ffffffff810580a8>] kthread+0xd2/0xda
>> [ 49.561678] [<ffffffff814bbf92>] ret_from_fork+0x22/0x40
>> [ 49.561679] [<ffffffff81057fd6>] ? kthread_worker_fn+0x13e/0x13e
>>
>> -ss
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
>> the body of a message to [email protected]
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 0734927..0c00928 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1276,6 +1276,7 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
> void __scsi_remove_device(struct scsi_device *sdev)
> {
> struct device *dev = &sdev->sdev_gendev;
> + struct scsi_target *starget;
>
> /*
> * This cleanup path is not reentrant and while it is impossible
> @@ -1315,7 +1316,9 @@ void __scsi_remove_device(struct scsi_device *sdev)
> * remoed sysfs visibility from the device, so make the target
> * invisible if this was the last device underneath it.
> */
> - scsi_target_reap(scsi_target(sdev));
> + starget = scsi_target(sdev);
> + starget->state = STARGET_REMOVE;
> + scsi_target_reap(starget);

Yes, scsi_target_reap is alse called from __scsi_remove_device, and ->state is
_RUNNING here.


>
> put_device(dev);
> }
>
>
>
> --
> Johannes Thumshirn Storage
> [email protected] +49 911 74053 689
> SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: Felix Imendörffer, Jane Smithard, Graham Norton
> HRB 21284 (AG Nürnberg)
> Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
>

2016-04-15 05:53:53

by Murphy Zhou

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

Hi,

On Wed, Apr 13, 2016 at 11:14 PM, James Bottomley
<[email protected]> wrote:
> On Wed, 2016-04-13 at 10:41 +0200, Johannes Thumshirn wrote:
>> Hi Sergey, Xiong,
>>
>> Can you try below patch?
>>
>> On Montag, 11. April 2016 18:01:47 CEST Sergey Senozhatsky wrote:
>> > Hello,
>> >
>> > commit 7b106f2de6938c31ce5e9c86bc70ad3904666b96
>> > Author: Johannes Thumshirn <[email protected]>
>> > Date: Tue Apr 5 11:50:44 2016 +0200
>> >
>> > scsi: Add intermediate STARGET_REMOVE state to
>> > scsi_target_state
>> >
>> >
>> > BUG_ON()s (next-20160411) each time I remove a usb flash
>> >
>> > [ 49.561600] [<ffffffffa0087f42>] scsi_target_destroy+0x5a/0xcb
>> > [scsi_mod]
>> > [ 49.561607] [<ffffffffa0089099>] scsi_target_reap+0x4a/0x4f
>> > [scsi_mod]
>> > [ 49.561613] [<ffffffffa008b453>] __scsi_remove_device+0xc3/0xd0
>> > [scsi_mod]
>> > [ 49.561619] [<ffffffffa0089d7b>] scsi_forget_host+0x52/0x63
>> > [scsi_mod]
>> > [ 49.561623] [<ffffffffa0080dbc>] scsi_remove_host+0x8c/0x102
>> > [scsi_mod]
>> > [ 49.561627] [<ffffffffa015c447>] usb_stor_disconnect+0x6b/0xab
>> > [usb_storage]
>> > [ 49.561634] [<ffffffffa0013f73>]
>> > usb_unbind_interface+0x77/0x1ca [usbcore]
>> > [ 49.561636] [<ffffffff813ae064>]
>> > __device_release_driver+0x9d/0x121
>> > [ 49.561638] [<ffffffff813ae10b>]
>> > device_release_driver+0x23/0x30
>> > [ 49.561639] [<ffffffff813ad2d1>] bus_remove_device+0xfb/0x10e
>> > [ 49.561641] [<ffffffff813aac05>] device_del+0x164/0x1e6
>> > [ 49.561648] [<ffffffffa0011b09>] ?
>> > remove_intf_ep_devs+0x3b/0x48 [usbcore]
>> > [ 49.561655] [<ffffffffa001200e>] usb_disable_device+0x84/0x1a5
>> > [usbcore]
>> > [ 49.561661] [<ffffffffa000ac7b>] usb_disconnect+0x94/0x19f
>> > [usbcore]
>> > [ 49.561667] [<ffffffffa000c2ab>] hub_event+0x5c1/0xdea
>> > [usbcore]
>> > [ 49.561670] [<ffffffff810530b1>] process_one_work+0x1dc/0x37f
>> > [ 49.561672] [<ffffffff81053dc5>] worker_thread+0x282/0x36d
>> > [ 49.561673] [<ffffffff81053b43>] ? rescuer_thread+0x2ae/0x2ae
>> > [ 49.561675] [<ffffffff810580a8>] kthread+0xd2/0xda
>> > [ 49.561678] [<ffffffff814bbf92>] ret_from_fork+0x22/0x40
>> > [ 49.561679] [<ffffffff81057fd6>] ?
>> > kthread_worker_fn+0x13e/0x13e
>> >
>> > -ss
>> > --
>> > To unsubscribe from this list: send the line "unsubscribe linux
>> > -scsi" in
>> > the body of a message to [email protected]
>> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>> >
>>
>> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
>> index 0734927..0c00928 100644
>> --- a/drivers/scsi/scsi_sysfs.c
>> +++ b/drivers/scsi/scsi_sysfs.c
>> @@ -1276,6 +1276,7 @@ int scsi_sysfs_add_sdev(struct scsi_device
>> *sdev)
>> void __scsi_remove_device(struct scsi_device *sdev)
>> {
>> struct device *dev = &sdev->sdev_gendev;
>> + struct scsi_target *starget;
>>
>> /*
>> * This cleanup path is not reentrant and while it is
>> impossible
>> @@ -1315,7 +1316,9 @@ void __scsi_remove_device(struct scsi_device
>> *sdev)
>> * remoed sysfs visibility from the device, so make the
>> target
>> * invisible if this was the last device underneath it.
>> */
>> - scsi_target_reap(scsi_target(sdev));
>> + starget = scsi_target(sdev);
>> + starget->state = STARGET_REMOVE;
>> + scsi_target_reap(starget);
>
> How about good grief no! A device with multiple targets will get it's
> lists screwed with this
>
> The STARGET_REMOVE state you added only applies to the case we're
> trying to kill a target. In the natural operation case, which is what
> everyone else is running into, we will try to remove a running target
> when it has no more scsi devices left on it. So the correct patch
> should be to make the BUG_ON see this:
>
> James
>
> ---
>
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 27df7e7..e0a78f5 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -319,8 +319,7 @@ static void scsi_target_destroy(struct scsi_target *starget)
> struct Scsi_Host *shost = dev_to_shost(dev->parent);
> unsigned long flags;
>
> - BUG_ON(starget->state != STARGET_REMOVE &&
> - starget->state != STARGET_CREATED);
> + BUG_ON(starget->state == STARGET_DEL);
> starget->state = STARGET_DEL;
> transport_destroy_device(dev);
> spin_lock_irqsave(shost->host_lock, flags);
>


This will survive modprobe -r scsi_debug ..

Just to make sure, is this _REMOVE state able to do the latter thing what it was
trying to do, in this way ?


commit 7b106f2de6938c31ce5e9c86bc70ad3904666b96
Author: Johannes Thumshirn <[email protected]>
Date: Tue Apr 5 11:50:44 2016 +0200

scsi: Add intermediate STARGET_REMOVE state to scsi_target_state

Add intermediate STARGET_REMOVE state to scsi_target_state to avoid
running into the BUG_ON() in scsi_target_reap(). The STARGET_REMOVE
state is only valid in the path from scsi_remove_target() to
scsi_target_destroy() indicating this target is going to be removed.

This re-fixes the problem introduced in commits bc3f02a795d3 ("[SCSI]
scsi_remove_target: fix softlockup regression on hot remove") and
40998193560d ("scsi: restart list search after unlock in
scsi_remove_target") in a more comprehensive way.

2016-04-15 20:56:30

by Martin K. Petersen

[permalink] [raw]
Subject: Re: [-next] BUG_ON in scsi_target_destroy()

>>>>> "James" == James Bottomley <[email protected]> writes:

James> The STARGET_REMOVE state you added only applies to the case we're
James> trying to kill a target. In the natural operation case, which is
James> what everyone else is running into, we will try to remove a
James> running target when it has no more scsi devices left on it. So
James> the correct patch should be to make the BUG_ON see this:

Commit amended.

--
Martin K. Petersen Oracle Linux Engineering