linux-kernel - Re: [PATCH] ASoC: simple-card: Fix refcount underflow

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Date:   Mon, 18 Feb 2019 08:52:26 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Daniel Baluta" <daniel.baluta@....com>
Cc:     "kuninori.morimoto.gx@...esas.com" <kuninori.morimoto.gx@...esas.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "vicencb@...il.com" <vicencb@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "dl-linux-imx" <linux-imx@....com>,
        "S.j. Wang" <shengjiu.wang@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: simple-card: Fix refcount underflow

On Mon, 18 Feb 2019 08:06:19 +0100,
Daniel Baluta wrote:
> 
> On Mon, 2019-02-18 at 10:37 +0900, Kuninori Morimoto wrote:
> > Hi Daniel, Mark, again
> > 
> > > > of_get_child_by_name() takes a reference we'll need to drop
> > > > later so when we substitute in top we need to take a reference
> > > > as well as just assigning.
> > > > 
> > > > Without this patch we hit the following error:
> > > > 
> > > > [    1.246852] OF: ERROR: Bad of_node_put() on /sound-wm8524
> > > > [    1.262261] Hardware name: NXP i.MX8MQ EVK (DT)
> > > > [    1.266807] Workqueue: events deferred_probe_work_func
> > > > [    1.271950] Call trace:
> > > > [    1.274406]  dump_backtrace+0x0/0x158
> > > > [    1.278074]  show_stack+0x14/0x20
> > > > [    1.281396]  dump_stack+0xa8/0xcc
> > > > [    1.284717]  of_node_release+0xb0/0xc8
> > > > [    1.288474]  kobject_put+0x74/0xf0
> > > > [    1.291879]  of_node_put+0x14/0x28
> > > > [    1.295286]  __of_get_next_child+0x44/0x70
> > > > [    1.299387]  of_get_next_child+0x3c/0x60
> > > > [    1.303315]  simple_for_each_link+0x1dc/0x230
> > > > [    1.307676]  simple_probe+0x80/0x540
> > > > [    1.311256]  platform_drv_probe+0x50/0xa0
> > > > 
> > > > This patch is based on an earlier version posted by Kuninori
> > > > Morimoto
> > > > and commit message includes explanations from Mark Brown.
> > > > 
> > > > 
> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fpatch%2F10814255%2F&amp;data=02%7C01%7Cdaniel.baluta%40nxp.com%7Ced1b7adc66a546c1bb4608d69541aaf8%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636860506617983174&amp;sdata=hTsurDLdtLAtTw0a5v%2FrSsleSawAP2yiVPl87%2BHCzTI%3D&amp;reserved=0
> > > > 
> > > > Reported-by: Vicente Bergas <vicencb@...il.com>
> > > > Signed-off-by: Daniel Baluta <daniel.baluta@....com>
> > > > ---
> > > 
> > > I'm not sure which one is correct in this case
> > > 
> > > Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
> > > 
> > > or
> > > 
> > > Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
> > 
> > And we want to add
> > 
> > Fixes: commit da215354eb55c ("ASoC: simple-card: merge simple-scu-
> > card")
> > 
> 
> Thanks! I thought about adding this but the current patch will not
> cleanly apply because of:
> 
> 2d01a84605a55c ("ASoC: simple-card: reduce naming prefix")

Yeah, it's a bit tricky because of the code change at this time.

At best, send two patches, once for 5.0 and once for 5.1, and let Mark
apply both of them and do the empty merge from 5.0 to 5.1, or let him
resolve the merge conflict by applying manually the 5.1 patch.


thanks,

Takashi