Re: [PATCH v4 2/7] Input: use input_device_enabled()

[Marek Szyprowski]

Hi Andrzej,

On 07.12.2020 16:50, Andrzej Pietrasiewicz wrote:
> Hi Marek,
>
> W dniu 07.12.2020 o 14:32, Marek Szyprowski pisze:
>> Hi Andrzej,
>>
>> On 08.06.2020 13:22, Andrzej Pietrasiewicz wrote:
>>> Use the newly added helper in relevant input drivers.
>>>
>>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>
>>
>> This patch landed recently in linux-next as commit d69f0a43c677 ("Input:
>> use input_device_enabled()"). Sadly it causes following warning during
>> system suspend/resume cycle on ARM 32bit Samsung Exynos5250-based Snow
>> Chromebook with kernel compiled from exynos_defconfig:
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 1777 at drivers/input/input.c:2230
>> input_device_enabled+0x68/0x6c
>> Modules linked in: cmac bnep mwifiex_sdio mwifiex sha256_generic
>> libsha256 sha256_arm cfg80211 btmrvl_sdio btmrvl bluetooth s5p_mfc
>> exynos_gsc v4l2_mem2mem videob
>> CPU: 0 PID: 1777 Comm: rtcwake Not tainted
>> 5.10.0-rc6-next-20201207-00001-g49a0dc04c46d-dirty #9902
>> Hardware name: Samsung Exynos (Flattened Device Tree)
>> [<c0111718>] (unwind_backtrace) from [<c010d050>] (show_stack+0x10/0x14)
>> [<c010d050>] (show_stack) from [<c0b32810>] (dump_stack+0xb4/0xd4)
>> [<c0b32810>] (dump_stack) from [<c0126e24>] (__warn+0xd8/0x11c)
>> [<c0126e24>] (__warn) from [<c0126f18>] (warn_slowpath_fmt+0xb0/0xb8)
>> [<c0126f18>] (warn_slowpath_fmt) from [<c07fa2fc>]
>> (input_device_enabled+0x68/0x6c)
>> [<c07fa2fc>] (input_device_enabled) from [<c080a0f8>]
>
> Apparently you are hitting this line of code in drivers/input/input.c:
>
> lockdep_assert_held(&dev->mutex);
>
> Inspecting input device's "users" member should happen under dev's lock.
>
This check and warning has been introduced by this patch. I assume that 
the suspend/resume paths are correct, but it looks that they were not 
tested with this patch thus it has not been noticed that they are not 
called under the input's lock. This needs a fix. Dmitry: how would you 
like to handle this issue?

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