[-next] BUG_ON in scsi_target_destroy()

[-next] BUG_ON in scsi_target_destroy()

[Sergey Senozhatsky]

Hello,

commit 7b106f2de6938c31ce5e9c86bc70ad3904666b96
Author: Johannes Thumshirn <jthumshirn@suse.de>
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

Re: [-next] BUG_ON in scsi_target_destroy()

[Johannes Thumshirn]

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 <jthumshirn@suse.de>
> 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 majordomo@vger.kernel.org
> 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
jthumshirn@suse.de                                                             +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

Re: [-next] BUG_ON in scsi_target_destroy()

[Johannes Thumshirn]

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
jthumshirn@suse.de                                                             +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

Re: [-next] BUG_ON in scsi_target_destroy()

[Sergey Senozhatsky]

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

Re: [-next] BUG_ON in scsi_target_destroy()

[James Bottomley]

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 <jthumshirn@suse.de>
> > 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 majordomo@vger.kernel.org
> > 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);

Re: [-next] BUG_ON in scsi_target_destroy()

[Sergey Senozhatsky]

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 <sergey.senozhatsky@gmail.com>

	-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);
> 

Re: [-next] BUG_ON in scsi_target_destroy()

[Xiong Zhou]

Hi,

On Wed, Apr 13, 2016 at 4:41 PM, Johannes Thumshirn <jthumshirn@suse.de> 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 <jthumshirn@suse.de>
>> 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 majordomo@vger.kernel.org
>> 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
> jthumshirn@suse.de                                                             +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
>

Re: [-next] BUG_ON in scsi_target_destroy()

[Xiong Zhou]

Hi,

On Wed, Apr 13, 2016 at 11:14 PM, James Bottomley
<jejb@linux.vnet.ibm.com> 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 <jthumshirn@suse.de>
>> > 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 majordomo@vger.kernel.org
>> > 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 <jthumshirn@suse.de>
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.

Re: [-next] BUG_ON in scsi_target_destroy()

[Martin K. Petersen]

>>>>> "James" == James Bottomley <jejb@linux.vnet.ibm.com> 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