linux-kernel - Re: [PATCH 5.15 000/159] 5.15.116-rc1 review

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Message-ID: <1e9e0ce4-dc47-81d6-e3a5-681d4a9ba9b0@roeck-us.net>
Date:   Sun, 11 Jun 2023 08:14:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Pavel Machek <pavel@...x.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, patches@...ts.linux.dev,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org, shuah@...nel.org, patches@...nelci.org,
        lkft-triage@...ts.linaro.org, jonathanh@...dia.com,
        f.fainelli@...il.com, sudipm.mukherjee@...il.com,
        srw@...dewatkins.net, rwarsow@....de,
        Thomas Gleixner <tglx@...utronix.de>,
        Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH 5.15 000/159] 5.15.116-rc1 review

On 6/10/23 14:14, Guenter Roeck wrote:
> Hi,
> 
> On 6/10/23 12:23, Pavel Machek wrote:
>> Hi!
>>
>>>> Build results:
>>>>     total: 155 pass: 155 fail: 0
>>>> Qemu test results:
>>>>     total: 499 pass: 498 fail: 1
>>>> Failed tests:
>>>>     arm:kudo-bmc:multi_v7_defconfig:npcm:usb0.1:nuvoton-npcm730-kudo:rootfs
>>>>
>>>> The test failure is spurious and not new. I observe it randomly on
>>>> multi_v7_defconfig builds, primarily on npcm platforms. There is no error
>>>> message, just a stalled boot. I have been trying to bisect for a while,
>>>> but I have not been successful so far. No immediate concern; I just wanted
>>>> to mention it in case someone else hits the same or a similar problem.
>>>>
>>>
>>> I managed to revise my bisect script sufficiently enough to get reliable
>>> results. It looks like the culprit is commit 503e554782c9 (" debugobject:
>>> Ensure pool refill (again)"); see bisect log below. Bisect on four
>>> different systems all have the same result. After reverting this patch,
>>> I do not see the problem anymore (again, confirmed on four different
>>> systems). If anyone has an idea how to debug this, please let me know.
>>> I'll be happy to give it a try.
>>
>> You may want to comment out debug_objects_fill_pool() in
>> debug_object_activate or debug_object_assert_init to see which one is
>> causing the failure...
>>
>> CONFIG_PREEMPT_RT is disabled for you, right? (Should 5.15 even have
>> that option?)
>>
> 
> CONFIG_PREEMPT_RT is disabled (it depends on ARCH_SUPPORTS_RT which is not
> enabled by any architecture in v5.15.y).
> 
> The added call in debug_object_activate() triggers the problem.
> Any idea what to do about it or how to debug it further ?
> 

I did some more debugging. The call to debug_object_activate()
from debug_hrtimer_activate() causes the immediate problem, and the
call from debug_timer_activate() causes a second (less likely) problem,
where the stall is seen during reboot.

In other words, the problem is (only) seen if DEBUG_OBJECTS_TIMERS
is enabled.

Guenter