linux-kernel - Re: [ata_scsi_offline_dev] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:238

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Date:   Tue, 7 Nov 2017 07:55:45 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Fengguang Wu <fengguang.wu@...el.com>
Cc:     IDE-ML <linux-ide@...r.kernel.org>, Christoph Hellwig <hch@....de>,
        Tejun Heo <tj@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>
Subject: Re: [ata_scsi_offline_dev] BUG: sleeping function called from invalid
 context at kernel/locking/mutex.c:238

On 11/07/2017 12:12 AM, Linus Torvalds wrote:
> On Mon, Nov 6, 2017 at 2:53 PM, Fengguang Wu <fengguang.wu@...el.com> wrote:
>>
>> The same dmesg happen to contain another libata related bug. Attached again.
>> It's rare and in the error handling path, so unlikely a new regression.
>>
>> [   49.608280] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:238
>> [   49.647821]  mutex_lock+0x20/0x50
>> [   49.651443]  kernfs_find_and_get_ns+0x23/0x60
>> [   49.656104]  sysfs_notify+0x77/0x90
>> [   49.659900]  scsi_device_set_state+0x63/0x150
>> [   49.664559]  ata_scsi_offline_dev+0x1c/0x30 [libata]
>> [   49.669817]  ata_eh_detach_dev+0x3b/0xb0 [libata]
> 
> ata_eh_detach_dev() does
> 
>         spin_lock_irqsave(ap->lock, flags);
> 
> and then does
> 
>         if (ata_scsi_offline_dev(dev)) {
>                 dev->flags |= ATA_DFLAG_DETACHED;
>                 ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG;
>         }
> 
> inside that spinlock. And this code is not new - it has done it since
> 2006 or so.
> 
> But it does seem to be a new regression in 4.14, caused by commit
> 8a97712e5314 ("scsi: make 'state' device attribute pollable"), because
> that's what added the sysfs_notify() call to scsi_device_set_state(),
> which made that spinlock be a problem.
> 
> That commit came in through the SCSI merge this merge window, and it
> seems to still revert cleanly.
> 
> So I do suspect that by now we should just revert that commit. It's
> not clear why that state attribute should be pollable, and the new
> code is clearly very much buggy.
> 
> Hannes, Martin?
> 
Seeing the complexity involved, yes, please revert that.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@...e.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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