Re: [PATCH v4 4/4] thermal: core: Add notifications call in the framework

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi Daniel,

On 15.07.2020 01:20, Daniel Lezcano wrote:
> On 13/07/2020 22:32, Daniel Lezcano wrote:
>> On 13/07/2020 11:31, Marek Szyprowski wrote:
>>> On 07.07.2020 11:15, Marek Szyprowski wrote:
>>>> On 06.07.2020 15:46, Daniel Lezcano wrote:
>>>>> On 06/07/2020 15:17, Marek Szyprowski wrote:
>>>>>> On 06.07.2020 12:55, Daniel Lezcano wrote:
>>>>>>> The generic netlink protocol is implemented but the different
>>>>>>> notification functions are not yet connected to the core code.
>>>>>>>
>>>>>>> These changes add the notification calls in the different
>>>>>>> corresponding places.
>>>>>>>
>>>>>>> Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
>>>>>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
>>>>>> This patch landed in today's linux-next 20200706 as commit 5df786e46560
>>>>>> ("thermal: core: Add notifications call in the framework"). Sadly it
>>>>>> breaks booting various Samsung Exynos based boards. Here is an example
>>>>>> log from Odroid U3 board:
>>>>>>
>>>>>> Unable to handle kernel NULL pointer dereference at virtual address
>>>>>> 00000010
>>>>>> pgd = (ptrval)
>>>>>> [00000010] *pgd=00000000
>>>>>> Internal error: Oops: 5 [#1] PREEMPT SMP ARM
>>>>>> Modules linked in:
>>>>>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.8.0-rc3-00015-g5df786e46560
>>>>>> #1146
>>>>>> Hardware name: Samsung Exynos (Flattened Device Tree)
>>>>>> PC is at kmem_cache_alloc+0x13c/0x418
>>>>>> LR is at kmem_cache_alloc+0x48/0x418
>>>>>> pc : [<c02b5cac>]    lr : [<c02b5bb8>]    psr: 20000053
>>>>>> ...
>>>>>> Flags: nzCv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment none
>>>>>> Control: 10c5387d  Table: 4000404a  DAC: 00000051
>>>>>> Process swapper/0 (pid: 1, stack limit = 0x(ptrval))
>>>>>> Stack: (0xee8f1cf8 to 0xee8f2000)
>>>>>> ...
>>>>>> [<c02b5cac>] (kmem_cache_alloc) from [<c08cd170>]
>>>>>> (__alloc_skb+0x5c/0x170)
>>>>>> [<c08cd170>] (__alloc_skb) from [<c07ec19c>]
>>>>>> (thermal_genl_send_event+0x24/0x174)
>>>>>> [<c07ec19c>] (thermal_genl_send_event) from [<c07ec648>]
>>>>>> (thermal_notify_tz_create+0x58/0x74)
>>>>>> [<c07ec648>] (thermal_notify_tz_create) from [<c07e9058>]
>>>>>> (thermal_zone_device_register+0x358/0x650)
>>>>>> [<c07e9058>] (thermal_zone_device_register) from [<c1028d34>]
>>>>>> (of_parse_thermal_zones+0x304/0x7a4)
>>>>>> [<c1028d34>] (of_parse_thermal_zones) from [<c1028964>]
>>>>>> (thermal_init+0xdc/0x154)
>>>>>> [<c1028964>] (thermal_init) from [<c0102378>]
>>>>>> (do_one_initcall+0x8c/0x424)
>>>>>> [<c0102378>] (do_one_initcall) from [<c1001158>]
>>>>>> (kernel_init_freeable+0x190/0x204)
>>>>>> [<c1001158>] (kernel_init_freeable) from [<c0ab85f4>]
>>>>>> (kernel_init+0x8/0x118)
>>>>>> [<c0ab85f4>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20)
>>>>>>
>>>>>> Reverting it on top of linux-next fixes the boot issue. I will
>>>>>> investigate it further soon.
>>>>> Thanks for reporting this.
>>>>>
>>>>> Can you send the addr2line result and code it points to ?
>>>> addr2line of c02b5cac (kmem_cache_alloc+0x13c/0x418) points to
>>>> mm/slub.c +2839, but I'm not sure if we can trust it. imho it looks
>>>> like some trashed memory somewhere, but I don't have time right now to
>>>> analyze it further now...
>>> Just one more thing I've noticed. The crash happens only if the kernel
>>> is compiled with old GCC (tested with arm-linux-gnueabi-gcc (Linaro GCC
>>> 4.9-2017.01) 4.9.4). If I compile kernel with newed GCC (like
>>> arm-linux-gnueabi-gcc (Linaro GCC 6.4-2017.11) 6.4.1 20171012), it works
>>> fine...
>>>
>>> This happens also with Linux next-20200710, which again got this commit.
>> So I finally succeed to reproduce on an ARM64 with a recent compiler,
>> earlycon, and the option CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
>
> Finally, narrowed down the issue.
>
>   - genetlink initialization is done at subsys initcall.
>   - thermal netlink init is done at core initcall
>   - netlink is done at core initcall
>
> By changing the order:
>
>   - netlink and genetlink at core initcall
>   - thermal init at postcore initcall
>
> That fixes the problem.
I confirm that such change fixes the issue! Feel free to add:

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

to the final patch.

> The genetlink initcall order is from 2005 and
> IMO it makes sense to come right after the netlink initialization.
>
> It is acceptable to have the thermal init at the postcore initcall. It
> is very recently we moved from fs_initcall to core_initcall.
>
> Thanks to Arnd who give me a direction to look at.
Best regards

-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland