Re: [PATCH 5.17 127/298] driver core: Fix wait_for_device_probe() & deferred_probe_timeout interaction

[Shreeya Patel <shreeya.patel@collabora.com>]

Hi Geert, Saravana,

On 18/08/23 00:03, Saravana Kannan wrote:
> On Thu, Aug 17, 2023 at 4:37 AM Shreeya Patel
> <shreeya.patel@collabora.com> wrote:
>> Hi Greg,
>>
>> On 16/08/23 20:33, Greg Kroah-Hartman wrote:
>>> On Wed, Aug 16, 2023 at 03:09:27PM +0530, Shreeya Patel wrote:
>>>> On 13/06/22 15:40, Greg Kroah-Hartman wrote:
>>>>> From: Saravana Kannan<saravanak@google.com>
>>>>>
>>>>> [ Upstream commit 5ee76c256e928455212ab759c51d198fedbe7523 ]
>>>>>
>>>>> Mounting NFS rootfs was timing out when deferred_probe_timeout was
>>>>> non-zero [1].  This was because ip_auto_config() initcall times out
>>>>> waiting for the network interfaces to show up when
>>>>> deferred_probe_timeout was non-zero. While ip_auto_config() calls
>>>>> wait_for_device_probe() to make sure any currently running deferred
>>>>> probe work or asynchronous probe finishes, that wasn't sufficient to
>>>>> account for devices being deferred until deferred_probe_timeout.
>>>>>
>>>>> Commit 35a672363ab3 ("driver core: Ensure wait_for_device_probe() waits
>>>>> until the deferred_probe_timeout fires") tried to fix that by making
>>>>> sure wait_for_device_probe() waits for deferred_probe_timeout to expire
>>>>> before returning.
>>>>>
>>>>> However, if wait_for_device_probe() is called from the kernel_init()
>>>>> context:
>>>>>
>>>>> - Before deferred_probe_initcall() [2], it causes the boot process to
>>>>>      hang due to a deadlock.
>>>>>
>>>>> - After deferred_probe_initcall() [3], it blocks kernel_init() from
>>>>>      continuing till deferred_probe_timeout expires and beats the point of
>>>>>      deferred_probe_timeout that's trying to wait for userspace to load
>>>>>      modules.
>>>>>
>>>>> Neither of this is good. So revert the changes to
>>>>> wait_for_device_probe().
>>>>>
>>>>> [1] -https://lore.kernel.org/lkml/TYAPR01MB45443DF63B9EF29054F7C41FD8C60@TYAPR01MB4544.jpnprd01.prod.outlook.com/
>>>>> [2] -https://lore.kernel.org/lkml/YowHNo4sBjr9ijZr@dev-arch.thelio-3990X/
>>>>> [3] -https://lore.kernel.org/lkml/Yo3WvGnNk3LvLb7R@linutronix.de/
>>>> Hi Saravana, Greg,
>>>>
>>>>
>>>> KernelCI found this patch causes the baseline.bootrr.deferred-probe-empty test to fail on r8a77960-ulcb,
>>>> see the following details for more information.
>>>>
>>>> KernelCI dashboard link:
>>>> https://linux.kernelci.org/test/plan/id/64d2a6be8c1a8435e535b264/
>>>>
>>>> Error messages from the logs :-
>>>>
>>>> + UUID=11236495_1.5.2.4.5
>>>> + set +x
>>>> + export 'PATH=/opt/bootrr/libexec/bootrr/helpers:/lava-11236495/1/../bin:/sbin:/usr/sbin:/bin:/usr/bin'
>>>> + cd /opt/bootrr/libexec/bootrr
>>>> + sh helpers/bootrr-auto
>>>> e6800000.ethernet
>>>> e6700000.dma-controller
>>>> e7300000.dma-controller
>>>> e7310000.dma-controller
>>>> ec700000.dma-controller
>>>> ec720000.dma-controller
>>>> fea20000.vsp
>>>> feb00000.display
>>>> fea28000.vsp
>>>> fea30000.vsp
>>>> fe9a0000.vsp
>>>> fe9af000.fcp
>>>> fea27000.fcp
>>>> fea2f000.fcp
>>>> fea37000.fcp
>>>> sound
>>>> ee100000.mmc
>>>> ee140000.mmc
>>>> ec500000.sound
>>>> /lava-11236495/1/../bin/lava-test-case
>>>> <8>[   17.476741] <LAVA_SIGNAL_TESTCASE TEST_CASE_ID=deferred-probe-empty RESULT=fail>
>>>>
>>>> Test case failing :-
>>>> Baseline Bootrr deferred-probe-empty test -https://github.com/kernelci/bootrr/blob/main/helpers/bootrr-generic-tests
>>>>
>>>> Regression Reproduced :-
>>>>
>>>> Lava job after reverting the commit 5ee76c256e92
>>>> https://lava.collabora.dev/scheduler/job/11292890
>>>>
>>>>
>>>> Bisection report from KernelCI can be found at the bottom of the email.
>>>>
>>>> Thanks,
>>>> Shreeya Patel
>>>>
>>>> #regzbot introduced: 5ee76c256e92
>>>> #regzbot title: KernelCI: Multiple devices deferring on r8a77960-ulcb
>>>>
>>>> ---------------------------------------------------------------------------------------------------------------------------------------------------
>>>>
>>>> * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * **
>>>> * If you do send a fix, please include this trailer: *
>>>> * Reported-by: "kernelci.org bot" <bot@...> *
>>>> * *
>>>> * Hope this helps! *
>>>> * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
>>>>
>>>> stable-rc/linux-5.10.y bisection: baseline.bootrr.deferred-probe-empty on
>>>> r8a77960-ulcb
>>> You are testing 5.10.y, yet the subject says 5.17?
>>>
>>> Which is it here?
>> Sorry, I accidentally used the lore link for 5.17 while reporting this
>> issue,
>> but this test does fail on all the stable releases from 5.10 onwards.
>>
>> stable 5.15 :-
>> https://linux.kernelci.org/test/case/id/64dd156a5ac58d0cf335b1ea/
>> mainline :-
>> https://linux.kernelci.org/test/case/id/64dc13d55cb51357a135b209/
>>
> Shreeya, can you try the patch Geert suggested and let us know if it
> helps? If not, then I can try to take a closer look.

I tried to test the kernel with 9be4cbd09da8 but it didn't change the 
result.
https://lava.collabora.dev/scheduler/job/11311615

Also, I am not sure if this can change things but just FYI, KernelCI 
adds some kernel parameters when running these tests and one of the 
parameter is deferred_probe_timeout=60.
You can check this in the definition details given in the Lava job. I 
also tried to remove this parameter and rerun the test but again I got 
the same result.

I will try to add 9be4cbd09da8 to mainline kernel and see what results I 
get.


Thanks,
Shreeya Patel

>
> -Saravana
>