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Subject: RE: Re: [syzbot] INFO: rcu detected stall in tx
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From:   Guido Kiener <Guido.Kiener@rohde-schwarz.com>
To:     Dmitry Vyukov <dvyukov@google.com>,
        syzbot <syzbot+e2eae5639e7203360018@syzkaller.appspotmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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Thread-Topic: Re: [syzbot] INFO: rcu detected stall in tx /cr/
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Date:   Mon, 19 Apr 2021 20:56:19 +0000
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Hi all,

The error is in usbtmc_interrupt(struct urb *urb) since five years. The status code EPROTO is not handled correctly.
It's not a showstopper, but we should fix it and check the status code according to usbtmc_read_bulk_cb() or
usb_skeleton.c.
@Dave: Do you have time? Otherwise I can do it.
@Greg: Is it urgent?

- Guido

-----Original Message-----
From: Dmitry 
Sent: Monday, April 19, 2021 9:27 AM
Subject: Re: [syzbot] INFO: rcu detected stall in tx

On Mon, Apr 19, 2021 at 9:19 AM syzbot
<syzbot+e2eae5639e7203360018@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    50987bec Merge tag 'trace-v5.12-rc7' of git://git.kernel.o..
> git tree:       upstream
> console output: 
> https://syzkaller.appspot.com/x/log.txt?x=1065c5fcd00000
> kernel config:  
> https://syzkaller.appspot.com/x/.config?x=398c4d0fe6f66e68
> dashboard link: 
> https://syzkaller.appspot.com/bug?extid=e2eae5639e7203360018
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e2eae5639e7203360018@syzkaller.appspotmail.com
>
> usbtmc 5-1:0.0: unknown status received: -71 usbtmc 3-1:0.0: unknown 
> status received: -71 usbtmc 5-1:0.0: unknown status received: -71

The log shows an infinite stream of these before the stall, so I assume it's an infinite loop in usbtmc.
+usbtmc maintainers

[  370.171634][    C0] usbtmc 6-1:0.0: unknown status received: -71
[  370.177799][    C1] usbtmc 3-1:0.0: unknown status received: -71
[  370.183912][    C0] usbtmc 4-1:0.0: unknown status received: -71
[  370.190076][    C1] usbtmc 5-1:0.0: unknown status received: -71
[  370.196194][    C0] usbtmc 2-1:0.0: unknown status received: -71
[  370.202387][    C1] usbtmc 3-1:0.0: unknown status received: -71
[  370.208460][    C0] usbtmc 6-1:0.0: unknown status received: -71
[  370.214615][    C1] usbtmc 5-1:0.0: unknown status received: -71
[  370.220736][    C0] usbtmc 4-1:0.0: unknown status received: -71
[  370.226902][    C1] usbtmc 3-1:0.0: unknown status received: -71
[  370.233005][    C0] usbtmc 2-1:0.0: unknown status received: -71
[  370.239168][    C1] usbtmc 5-1:0.0: unknown status received: -71
[  370.245271][    C0] usbtmc 6-1:0.0: unknown status received: -71
[  370.251426][    C1] usbtmc 3-1:0.0: unknown status received: -71
[  370.257552][    C0] usbtmc 4-1:0.0: unknown status received: -71
[  370.263715][    C1] usbtmc 5-1:0.0: unknown status received: -71
[  370.269819][    C0] usbtmc 2-1:0.0: unknown status received: -71
[  370.275974][    C1] usbtmc 3-1:0.0: unknown status received: -71
[  370.282100][    C0] usbtmc 6-1:0.0: unknown status received: -71
[  370.288262][    C1] usbtmc 5-1:0.0: unknown status received: -71
[  370.294399][    C0] usbtmc 4-1:0.0: unknown status received: -71


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