Re: [-next] BUG_ON in scsi_target_destroy()

[Xiong Zhou <jencce.kernel@gmail.com>]

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
>> > --
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>> > -scsi" in
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>> >
>>
>> 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.