linux-kernel - Re: [PATCH] x86/debug: Handle warnings before the notifier chain

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Message-ID: <87o9qyy4hb.fsf@ashishki-desk.ger.corp.intel.com>
Date:   Tue, 29 Aug 2017 14:53:52 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Richard Weinberger <richard.weinberger@...il.com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Jason Wessel <jason.wessel@...driver.com>
Subject: Re: [PATCH] x86/debug: Handle warnings before the notifier chain

Peter Zijlstra <peterz@...radead.org> writes:

> On Mon, Jul 24, 2017 at 01:04:28PM +0300, Alexander Shishkin wrote:
>> Commit
>> 
>>   9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
>> 
>> turned warnings into UD0, but the fixup code only runs after the
>> notify_die() chain. This is a problem, in particular, with kgdb,
>> which kicks in as if it was a BUG().
>> 
>> Fix this by running the fixup code before the notifier chain in
>> the invalid op handler path.
>
> So arguable it might be nice to have kgdb trap on a WARN, but it
> treating it as a BUG is obviously undesirable.
>
> Jason, what would you want kgdb to do here?

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