linux-kernel - Re: UART/TTY console deadlock

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Message-ID: <CAHQZ30BEe4uPJ=7TZWAd5XtjKjFcjcfhr8GMaR6GKmEMrcTVqQ@mail.gmail.com>
Date:   Tue, 14 Jul 2020 10:16:07 -0600
From:   Raul Rangel <rrangel@...gle.com>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "S, Shirish" <Shirish.S@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        John Ogness <john.ogness@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: UART/TTY console deadlock

Hey everyone,
So it looks like this was a red herring. We were getting spurious
interrupts which I suspect caused the console code to get called in
some critical section. Once we fixed the spurious interrupts we no
longer see the issue. Sorry for the noise.

Thanks,
Raul

On Thu, Jul 9, 2020 at 7:22 AM Sergey Senozhatsky
<sergey.senozhatsky@...il.com> wrote:
>
> On (20/07/08 11:52), Petr Mladek wrote:
> >
> > I still believe that this is a false positive.
>
> I've no problems with that. The thing that I'm trying to improve here is the
> fact that from lockdep's point of view there are no false positives. lockdep
> reports the problem and then waves good bye. It disables itself. There might
> be some real suspend locking problems on some particular setups, but it's
> hard to tell, because console startup blows up the lockdep first.
>
>         -ss