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

From: Shreeya Patel
Date: Thu Aug 17 2023 - 07:38:14 EST


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@xxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
[2] -https://lore.kernel.org/lkml/YowHNo4sBjr9ijZr@dev-arch.thelio-3990X/
[3] -https://lore.kernel.org/lkml/Yo3WvGnNk3LvLb7R@xxxxxxxxxxxxx/
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/

Thanks,
Shreeya Patel


confused,

greg k-h