[Letux-kernel] [Gta04-owner] New LetuxOS Kernels

[Andreas Kemnade]

Hi,

On Tue, 19 Jun 2018 20:07:23 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> [technical discussions should go to the proper mailing lists]
> 
> Hi Andreas,
> 
> > Am 19.06.2018 um 19:46 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> > 
> > Hi,
> >   
> >> Am 19.06.2018 um 19:22 schrieb Andreas Kemnade <andreas at kemnade.info>:
> >> 
> >> On Tue, 19 Jun 2018 11:38:26 +0200
> >> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> >>   
> >>> Hi,
> >>> we did hunt a while for a big bug in the kernel.
> >>> It was a little flaky and random but the main
> >>> symptom was a kernel NULL pointer panic in
> >>> strcmp().
> >>> 
> >>> The result was that the GTA04 (and also the Pyra)
> >>> did not continue to boot properly. Sometimes it
> >>> came to a login: but then several drivers were
> >>> missing.
> >>> 
> >>> After hunting down the bug it was not a device
> >>> driver but a race and dangling pointer problem
> >>> in the pincontrol subsystem.
> >>> 
> >>> Now we got some patches from the maintainer and
> >>> the problem seems to have disappeared.
> >>> 
> >>> Well, has it or hasn't is?  
> >> 
> >> compiled dca26f608a765008b869991bf29fa241769599fb + my compile fix
> >> 
> >> result: strcmp problem again.
> >> [    7.335571] [<c074abc0>] (strcmp) from [<c04266bc>] (pinctrl_generic_add_group+0x50/0xc4)
> >> [    7.344116] [<c04266bc>] (pinctrl_generic_add_group) from [<c042b920>] (pcs_dt_node_to_map+0x484/0x820)
> >> [    7.353912] [<c042b920>] (pcs_dt_node_to_map) from [<c04298f4>] (pinctrl_dt_to_map+0x220/0x2bc)
> >> [    7.363006] [<c04298f4>] (pinctrl_dt_to_map) from [<c04269c4>] (create_pinctrl+0x5c/0x318)  
> > 
> > Hm...
> > 
> > I did a quick boot - and on first boot I also got a strcmp(NULL).
> > From the SD card which I had used for extensive testing yesterday.
> > 
> > What the hell is going on here?  
> 
> Maybe it is still a bug to devm_kzalloc something and store in the radix
> tree and leave it there, even if the driver is detached?
> 
> Then we still try to access this memory region by scanning the tree.
> 
> For test purposes we could replace the devm_kzalloc by kzalloc. This
> whould leak a little memory, but my hope is that the problem disappears.
> 
> Do you have a repeatable (at least >some%) scenario to reproduce the
> bug?

unfortunately not, maybe we should pass init=/modprobe-mess.sh to
kernel commandline, and create a worst case modprobe scenario there.
So we can control probing order more.

Regards,
Andreas
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