[alsa-devel] [PATCH] device property: Fix usecount for of_graph_get_port_parent()

[Kuninori Morimoto]

Hi

> 8< ------
> From tony Mon Sep 17 00:00:00 2001
> From: Tony Lindgren <tony at atomide.com>
> Date: Thu, 27 Jul 2017 01:30:16 -0700
> Subject: [PATCHv2] device property: Fix usecount for
>  of_graph_get_port_parent()
> 
> Fix inconsistent use of of_graph_get_port_parent() where
> asoc_simple_card_parse_graph_dai() does of_node_get() before
> calling it while other callers do not. We can fix this by
> not trashing the node passed to of_graph_get_port_parent().
> 
> Let's also make sure the callers have correct refcounts and remove
> related incorrect of_node_put() calls for of_for_each_phandle
> as that's done by of_phandle_iterator_next() except when
> we break out of the loop early.
> 
> Let's fix both issues with a single patch to avoid kobject
> refcounts getting messed up more if two patches are merged
> separately.
> 
> Otherwise strange issues can happen caused by memory corruption
> caused by too many kobject_del() calls such as:
> 
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:747
> ...
> (___might_sleep)
> (__mutex_lock)
> (mutex_lock_nested)
> (kernfs_remove)
> (kobject_del)
> (kobject_put)
> (of_get_next_parent)
> (of_graph_get_port_parent)
> (asoc_simple_card_parse_graph_dai [snd_soc_simple_card_utils])
> (asoc_graph_card_probe [snd_soc_audio_graph_card])
> 
> Fixes: 0ef472a973eb ("of_graph: add of_graph_get_port_parent()")
> Fixes: 2692c1c63c29 ("ASoC: add audio-graph-card support")
> Fixes: 1689333f8311 ("ASoC: simple-card-utils: add asoc_simple_card_parse_graph_dai()")
> Cc: Mark Brown <broonie at kernel.org>
> Cc: Takashi Iwai <tiwai at suse.com>
> Cc: Kuninori Morimoto <kuninori.morimoto.gx at renesas.com>
> Cc: alsa-devel at alsa-project.org
> Signed-off-by: Tony Lindgren <tony at atomide.com>
> ---

This fixes audio-graph-scu-card (+ Renesas Salvator-X board) side issue, too

Tested-by: Kuninori Morimoto <kuninori.morimoto.gx at renesas.com>

Best regards
---
Kuninori Morimoto