linux-kernel - Re: mainline/master boot bisection: v4.20-rc5-79-gabb8d6ecbd8f on jetson-tk1

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Date:   Mon, 10 Dec 2018 18:14:06 +0000
From:   Guillaume Tucker <guillaume.tucker@...labora.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        tomeu.vizoso@...labora.com, Oleg Nesterov <oleg@...hat.com>,
        broonie@...nel.org, matthew.hart@...aro.org, khilman@...libre.com,
        enric.balletbo@...labora.com,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        kernel@...labora.com
Subject: Re: mainline/master boot bisection: v4.20-rc5-79-gabb8d6ecbd8f on
 jetson-tk1

On 10/12/2018 10:53, Ravi Bangoria wrote:
> Hi,
> 
> Can you please provide more details. I don't understand how this patch
> can cause boot failure.

The kernel Oops caused by the nouveau driver was treated as a
boot failure in the BayLibre lab, although it did not necessarily
mean the kernel had failed to boot to a login prompt.  This
configuration has now been changed to stop reporting things like
NULL pointer dereferences as boot failures, the only criteria for
a KernelCI boot test being to be able to get to the login prompt.

Side note: We may start reporting non-fatal errors found in the
kernel log somehow as part of an extended boot test with some
extra checks in the future, but that's a different topic.

> From the log found at
> https://storage.kernelci.org/mainline/master/v4.20-rc5-79-gabb8d6ecbd8f/arm/multi_v7_defconfig+CONFIG_EFI=y+CONFIG_ARM_LPAE=y/lab-baylibre/boot-tegra124-jetson-tk1.html
> 
[...]
> 
> 
> Both PC and LR are pointing to drm_* code. I don't see this anyway related to
> uprobes. Did I miss anything?

So for this particular bisection, there is a known problem in the
nouveau driver, pending this fix to be applied:

  https://patchwork.freedesktop.org/patch/263587/

I haven't investigated how your patch in uprobes.c makes the
issue appear in the nouveau driver but I suspect it's merely
uncovering it.  The patch linked above does fix the actual
problem in the nouveau driver.

>> * This automated bisection report was sent to you on the basis  *
>> * that you may be involved with the breaking commit it has      *
>> * found.  No manual investigation has been done to verify it,   *
>> * and the root cause of the problem may be somewhere else.      *

Seems like this is just what happened in this case.

Guillaume