linux-kernel - Re: Re: Re: Re: Re: Re: [syzbot] INFO: rcu detected stall in tx

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Message-ID: <20210519180414.GL2549456@dell>
Date:   Wed, 19 May 2021 19:04:14 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Guido Kiener <Guido.Kiener@...de-schwarz.com>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        dave penkler <dpenkler@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot <syzbot+e2eae5639e7203360018@...kaller.appspotmail.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB list <linux-usb@...r.kernel.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "dwmw@...zon.co.uk" <dwmw@...zon.co.uk>,
        "hpa@...or.com" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: Re: Re: Re: Re: Re: [syzbot] INFO: rcu detected stall in tx

On Wed, 19 May 2021, Guido Kiener wrote:

> > On Wed, May 19, 2021 at 10:48:29AM +0200, dave penkler wrote:
> > > On Sat, 8 May 2021 at 16:29, Alan Stern <stern@...land.harvard.edu> wrote:
> > > >
> > > > On Sat, May 08, 2021 at 10:14:41AM +0200, dave penkler wrote:
> > > > > When the host driver detects a protocol error while processing an
> > > > > URB it completes the URB with EPROTO status and marks the endpoint
> > > > > as halted.
> > > >
> > > > Not true.  It does not mark the endpoint as halted, not unless it
> > > > receives a STALL handshake from the device.  A STALL is not a
> > > > protocol error.
> > > >
> > > > > When the class driver resubmits the URB and the if the host driver
> > > > > finds the endpoint still marked as halted it should return EPIPE
> > > > > status on the resubmitted URB
> > > >
> > > > Irrelevant.
> > > Not at all. The point is that when an application is talking to an
> > > instrument over the usbtmc driver, the underlying host controller and
> > > its driver will detect and silence a babbling endpoint.
> > 
> > No, they won't.  That is, they will detect a babble error and return an error status, but
> > they won't silence the endpoint.  What makes you think they will?
> 
> Maybe there is a misunderstanding. I guess that Dave wanted to propose:
> "EPROTO is a link level issue and needs to be handled by the host driver.
> When the host driver detects a protocol error while processing an
> URB it SHOULD complete the URB with EPROTO status and SHOULD mark the endpoint
> as halted."
> Is this a realistic fix for all host drivers?
> 
> -Guido

Guido, would you mind taking a look at your mailer settings please?  I
now have >=7 threads running through my inbox with the same subject.
For some reason your mailer is insisting on creating a new one for
each of your replies.

It's also adding odd "re: re: re: ..." prefixes.

TIA

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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