Bug 215542

Summary:	rtl8723bs (SDIO) - Access point mode causes a kernel panic
Product:	Drivers	Reporter:	José Ángel Pastrana (japp.debian)
Component:	Staging	Assignee:	drivers_staging (drivers_staging)
Status:	RESOLVED CODE_FIX
Severity:	normal	CC:	fabioaiuto83, jwrdegoede
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	5.15.15	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	kernel panic CONFIG_LOCKDEP=y Patch removing unneeded lock [PATCH] staging: rtl8723bs: Fix access-point mode deadlock Configuration files

Description José Ángel Pastrana 2022-01-28 12:48:46 UTC

Created attachment 300343 [details]
kernel panic

When I use r8723bs (sdio) as access point and a client begins a intensive download or speed test, a kernel panic ocurrs (see attachment). I can reproduce this bug consistently.

Also, I have bisected the kernel source code and happens for first time with the following commit:

commit 54659ca026e586bbb33a7e60daa6443a3ac6b5df
Author: Fabio Aiuto <fabioaiuto83@gmail.com>
Date:   Mon Sep 20 16:55:00 2021 +0200

    staging: rtl8723bs: remove possible deadlock when disconnect (v2)

Comment 1 Hans de Goede 2022-02-17 13:13:08 UTC

Thank you for your bug-report. Can you please enable the kernel's lockdep feature (CONFIG_LOCKDEP=y) and then reproduce with that enabled and collect logs again ?

That should help with figuring out what is going on here.

Comment 2 José Ángel Pastrana 2022-02-20 23:06:38 UTC

Created attachment 300495 [details]
CONFIG_LOCKDEP=y

I uploaded a new attachment: lockdep.txt. Kernel 5.16.7 recompiled with CONFIG_LOCKDEP=y as you suggested.

Comment 3 Fabio Aiuto 2022-02-26 11:31:57 UTC

Created attachment 300510 [details]
Patch removing unneeded lock

Comment 4 Fabio Aiuto 2022-02-26 11:34:11 UTC

Hello Jose Angel,

thanks for filing this. Could you tell me if the patch fixes the issue?
Thanks a lot.

Comment 5 José Ángel Pastrana 2022-03-01 08:20:09 UTC

Thanks Fabio, I have tested your patch and the kernel panic has gone!

I am going to use it daily, this patch is enough fine for me.

Thanks a lot again, Fabio and Hans.

Comment 6 Fabio Aiuto 2022-03-01 08:36:23 UTC

Hello José,

On Tue, Mar 01, 2022 at 08:20:09AM +0000, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=215542
> 
> --- Comment #5 from José Ángel Pastrana (japp.debian@gmail.com) ---
> Thanks Fabio, I have tested your patch and the kernel panic has gone!

good to hear. Please feel free to do some stress tests if you need and
try in STA mode, anyway STA mode should be fine.

> 
> I am going to use it daily, this patch is enough fine for me.
> 
> Thanks a lot again, Fabio and Hans.

Happy to help,

fabio

> 
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Comment 7 Hans de Goede 2022-03-01 21:45:53 UTC

Hi José,

Thank you for reporting and testing this. Unfortunately Fabio's fix only fixes one possible deadlock and further analysis has shown that there are other problematic parts also introduced by the commit your bisect found.

Since that commit another, extra fix for the same locking issue has landed:
commit a7ac783c338b ("staging: rtl8723bs: remove a second possible deadlock")

which should fix the original issue even if the bad commit you found is reverted.

So after some further analysis, I believe it is best to just revert the bad commit.

I'm attaching a patch which does the revert (untested so far) if you can give this a test in access-point mode that would be great. I will run some tests in normal client mode myself tomorrow.

Comment 8 Hans de Goede 2022-03-01 21:46:21 UTC

Created attachment 300516 [details]
[PATCH] staging: rtl8723bs: Fix access-point mode deadlock

Comment 9 José Ángel Pastrana 2022-03-03 07:31:44 UTC

Hi Hans and Fabio,

Fabio, I had no problems with sta mode, but also I was testing both sta and access point mode.

Hans, about your latest patch, it worked pretty well and I didn't find any problem.

Comment 10 Fabio Aiuto 2022-03-03 07:38:31 UTC

Hello José,

good to hear, anyway Hans's patches works better, are cleaner and cover
all known cases, they have just been accepted upstream and soon will be
mainline.

Thank you for your testing.

Please could you share the setup you have for AP mode testing?
(configuration files)

Thanks a lot,

Fabio

Comment 11 José Ángel Pastrana 2022-03-03 10:29:05 UTC

Created attachment 300525 [details]
Configuration files

Hello Fabio,

I use hostapd 2.9 and dnsmasq 2.86. Check out the attachment file: setup-ap.tgz

Comment 12 Fabio Aiuto 2022-03-03 10:36:00 UTC

Thanks!

fabio

Comment 13 José Ángel Pastrana 2022-06-20 05:48:56 UTC

The code fix was merged into the Linux kernel 5.18 several months ago [1] and I have been testing it since it was released until today. As this issue was solved finally, I am closing the bug report now.

Thanks to all

[1] https://github.com/torvalds/linux/commit/8f4347081be32e67b0873827e0138ab0fdaaf450