linux-kernel - Re: [PATCH] ARM: Fix null die() string for unhandled data and prefetch abort cases

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Message-ID: <20190725215540.GM1330@shell.armlinux.org.uk>
Date:   Thu, 25 Jul 2019 22:55:40 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     "George G. Davis" <george_davis@...tor.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Allison Randal <allison@...utok.net>,
        Souptick Joarder <jrdr.linux@...il.com>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: Fix null die() string for unhandled data and
 prefetch abort cases

On Thu, Jul 25, 2019 at 05:37:54PM -0400, George G. Davis wrote:
> Hello Russell,
> 
> Thanks for your prompt reply!
> 
> On Sat, Jul 20, 2019 at 01:30:23PM +0100, Russell King - ARM Linux admin wrote:
> > On Fri, Jul 19, 2019 at 10:32:55PM -0400, George G. Davis wrote:
> > > When an unhandled data or prefetch abort occurs, the die() string
> > > is empty resulting in backtrace messages similar to the following:
> > > 
> > > 	Internal error: : 1 [#1] PREEMPT SMP ARM
> > > 
> > > Replace the null string with the name of the abort handler in order
> > > to provide more meaningful hints as to the cause of the fault.
> > 
> > NAK.
> > 
> > We already print the cause of the abort earlier in the dump, and we've
> > also added a "cut here" marker to help people include all the necessary
> > information when reporting a problem.
> 
> For what it's worth, I often receive crash dumps which lack the pr_alert
> messages and only include the pr_emerg messages which this change would at
> least provide extra hints, since the "Internal error" as at EMERG level
> wereas the initial messages are only at ALERT level. It's subtle but for
> cases where the end user has set loglevel such that they only see EMERG
> messages, the change is helpful, to me at least.
> 
> > It's unfortunate that we have the additional colon in the oops dump,
> 
> Agreed, it's rather unfortunate that the string is NULL in these cases.
> 
> > but repeating the information that we've printed on one of the previous
> > two lines is really not necessary.
> 
> It depends on the loglevel the user has set. So perhaps it's not such a
> bad thing to repeat the information?

Or maybe we should arrange for consistent usage of the log levels?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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