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

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

On 19/08/23 01:49, Saravana Kannan wrote:
> On Thu, Aug 17, 2023 at 4:13 PM Shreeya Patel
> <shreeya.patel@collabora.com> wrote:
>> 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.
> Ah this is good to know.
>
>> 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.
> How long does the test wait after boot before checking for the
> deferred devices list?
>

AFAIK, script for running the tests is immediately ran after the boot 
process is complete so there is no wait time.

>> I will try to add 9be4cbd09da8 to mainline kernel and see what results I
>> get.
> Now I'm confused. What do you mean by mainline? Are you saying the tip
> of tree of Linus's tree is also hitting this issue?


KernelCI runs tests on different kernel branches and trees, we also have 
this same test running on mainline tree.
Following is the link to the dashboard for it and as you can see, it 
does fail there too.


https://linux.kernelci.org/test/case/id/64dc13d55cb51357a135b209/


> -Saravana
>