[PATCH] ALSA: core: Warn on empty module

[Marek Szyprowski]

On 30.06.2020 14:34, Nicolas Saenz Julienne wrote:
> Hi Marek,
> Thanks for pointing this out!
>
> On Tue, 2020-06-30 at 14:30 +0200, Marek Szyprowski wrote:
>> Hi
>>
>> On 24.06.2020 18:03, Takashi Iwai wrote:
>>> The module argument passed to snd_card_new() must be a valid non-NULL
>>> pointer when the module support is enabled.  Since ASoC driver passes
>>> the argument from each snd_soc_card definition, one may forget to set
>>> the owner field and lead to a NULL module easily.
>>>
>>> For catching such an overlook, add a WARN_ON() in snd_card_new().
>>> Also, put the card->module assignment in the ifdef block for a very
>>> minor optimization.
>>>
>>> Signed-off-by: Takashi Iwai <tiwai at suse.de>
>> I know that this is intended, but I would like to note that this patch
>> reveals the following issue on Raspberry Pi 3B with ARM 32bit kernel
>> compiled from multi_v7_defconfig:
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 1 PID: 210 at sound/core/init.c:207
>> snd_card_new+0x378/0x398 [snd]
>> Modules linked in: vc4(+) snd_soc_core ac97_bus snd_pcm_dmaengine
>> bluetooth snd_pcm snd_timer crc32_arm_ce raspberrypi_hwmon snd soundcore
>> ecdh_generic ecc bcm2835_thermal phy_generic
>> CPU: 1 PID: 210 Comm: systemd-udevd Not tainted
>> 5.8.0-rc1-00027-g81033c6b584b #1087
>> Hardware name: BCM2835
>> [<c03113c0>] (unwind_backtrace) from [<c030bcb4>] (show_stack+0x10/0x14)
>> [<c030bcb4>] (show_stack) from [<c071cef8>] (dump_stack+0xd4/0xe8)
>> [<c071cef8>] (dump_stack) from [<c0345bfc>] (__warn+0xdc/0xf4)
>> [<c0345bfc>] (__warn) from [<c0345cc4>] (warn_slowpath_fmt+0xb0/0xb8)
>> [<c0345cc4>] (warn_slowpath_fmt) from [<bf02ff74>]
>> (snd_card_new+0x378/0x398 [snd])
>> [<bf02ff74>] (snd_card_new [snd]) from [<bf11f0b4>]
>> (snd_soc_bind_card+0x280/0x99c [snd_soc_core])
>> [<bf11f0b4>] (snd_soc_bind_card [snd_soc_core]) from [<bf12f000>]
>> (devm_snd_soc_register_card+0x34/0x6c [snd_soc_core])
>> [<bf12f000>] (devm_snd_soc_register_card [snd_soc_core]) from
>> [<bf165654>] (vc4_hdmi_bind+0x43c/0x5f4 [vc4])
>> [<bf165654>] (vc4_hdmi_bind [vc4]) from [<c09d660c>]
>> (component_bind_all+0xec/0x24c)
>> [<c09d660c>] (component_bind_all) from [<bf15c44c>]
>> (vc4_drm_bind+0xd4/0x174 [vc4])
>> [<bf15c44c>] (vc4_drm_bind [vc4]) from [<c09d6ac0>]
>> (try_to_bring_up_master+0x160/0x1b0)
>> [<c09d6ac0>] (try_to_bring_up_master) from [<c09d6f38>]
>> (component_master_add_with_match+0xd0/0x104)
>> [<c09d6f38>] (component_master_add_with_match) from [<bf15c588>]
>> (vc4_platform_drm_probe+0x9c/0xbc [vc4])
>> [<bf15c588>] (vc4_platform_drm_probe [vc4]) from [<c09df740>]
>> (platform_drv_probe+0x6c/0xa4)
>> [<c09df740>] (platform_drv_probe) from [<c09dd6f0>]
>> (really_probe+0x210/0x350)
>> [<c09dd6f0>] (really_probe) from [<c09dd940>]
>> (driver_probe_device+0x5c/0xb4)
>> [<c09dd940>] (driver_probe_device) from [<c09ddb38>]
>> (device_driver_attach+0x58/0x60)
>> [<c09ddb38>] (device_driver_attach) from [<c09ddbc0>]
>> (__driver_attach+0x80/0xbc)
>> [<c09ddbc0>] (__driver_attach) from [<c09db820>]
>> (bus_for_each_dev+0x68/0xb4)
>> [<c09db820>] (bus_for_each_dev) from [<c09dc9f8>]
>> (bus_add_driver+0x130/0x1e8)
>> [<c09dc9f8>] (bus_add_driver) from [<c09de648>] (driver_register+0x78/0x110)
>> [<c09de648>] (driver_register) from [<c0302038>]
>> (do_one_initcall+0x50/0x220)
>> [<c0302038>] (do_one_initcall) from [<c03db544>] (do_init_module+0x60/0x210)
>> [<c03db544>] (do_init_module) from [<c03da4f8>] (load_module+0x1e34/0x2338)
>> [<c03da4f8>] (load_module) from [<c03dac00>] (sys_finit_module+0xac/0xbc)
>> [<c03dac00>] (sys_finit_module) from [<c03000c0>]
>> (ret_fast_syscall+0x0/0x54)
>> Exception stack(0xeded9fa8 to 0xeded9ff0)
>> ...
>> ---[ end trace 6414689569c2bc08 ]---
>>
>> This warning is not present when booting ARM 64bit kernel, but I suspect
>> that this is due to the differences in the kernel configuration.
> It's because vc4 is not yet supported on RPi4.

This happens on RPi *3B* :)


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