linux-kernel - Re: [PATCH v2] ARM: OMAP2+: Fix device node reference counts

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Date:   Wed, 1 Mar 2017 10:04:39 -0800
From:   Tony Lindgren <tony@...mide.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Paul Walmsley <paul@...an.com>,
        Russell King <linux@...linux.org.uk>,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Qi Hou <qi.hou@...driver.com>,
        Peter Rosin <peda@...ntia.se>, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v2] ARM: OMAP2+: Fix device node reference counts

* Guenter Roeck <linux@...ck-us.net> [170228 11:55]:
> After commit 'of: fix of_node leak caused in of_find_node_opts_by_path',
> the following error may be reported when running omap images.
> 
> OF: ERROR: Bad of_node_put() on /ocp@...00000
> CPU: 0 PID: 0 Comm: swapper Not tainted 4.10.0-rc7-next-20170210 #1
> Hardware name: Generic OMAP3-GP (Flattened Device Tree)
> [<c0310604>] (unwind_backtrace) from [<c030bbf4>] (show_stack+0x10/0x14)
> [<c030bbf4>] (show_stack) from [<c05add8c>] (dump_stack+0x98/0xac)
> [<c05add8c>] (dump_stack) from [<c05af1b0>] (kobject_release+0x48/0x7c)
> [<c05af1b0>] (kobject_release)
> 	from [<c0ad1aa4>] (of_find_node_by_name+0x74/0x94)
> [<c0ad1aa4>] (of_find_node_by_name)
> 	from [<c1215bd4>] (omap3xxx_hwmod_is_hs_ip_block_usable+0x24/0x2c)
> [<c1215bd4>] (omap3xxx_hwmod_is_hs_ip_block_usable) from
> [<c1215d5c>] (omap3xxx_hwmod_init+0x180/0x274)
> [<c1215d5c>] (omap3xxx_hwmod_init)
> 	from [<c120faa8>] (omap3_init_early+0xa0/0x11c)
> [<c120faa8>] (omap3_init_early)
> 	from [<c120fb2c>] (omap3430_init_early+0x8/0x30)
> [<c120fb2c>] (omap3430_init_early)
> 	from [<c1204710>] (setup_arch+0xc04/0xc34)
> [<c1204710>] (setup_arch) from [<c1200948>] (start_kernel+0x68/0x38c)
> [<c1200948>] (start_kernel) from [<8020807c>] (0x8020807c)
> 
> of_find_node_by_name() drops the reference to the passed device node.
> Use of_get_child_by_name() instead. Also, release references to
> device nodes obtained with of_find_node_by_name() and
> of_get_child_by_name() after they are no longer needed.
> 
> While at it, clean up the code and change the return type of
> omap3xxx_hwmod_is_hs_ip_block_usable() to bool to match its use
> and the return type of of_device_is_available().
> 
> Cc: Qi Hou <qi.hou@...driver.com>
> Cc: Peter Rosin <peda@...ntia.se>
> Cc: Rob Herring <robh@...nel.org>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
> v2: Change subject ('Grab reference to device nodes where needed'
>     didn't really cover all the changes made)
>     Use of_get_child_by_name() instead of of_find_node_by_name()
>     Drop references to device nodes as needed
>     Change return type of omap3xxx_hwmod_is_hs_ip_block_usable()
>     to bool

OK so now we have a commit id for it and should have:

Fixes: 0549bde0fcb1 ("of: fix of_node leak caused in
of_find_node_opts_by_path")

What about other leaky users of of_find_node_by_name() and
of_get_child_by_name()?

We have those in:

control.c
display.c
omap_device.c
omap_hwmod.c

So probably it really should be two fixes, one for the regression
causing the error. Then another one for fixing the leaky np use.

Sorry for going back and forth here, I guess I did not full understand
the second part of the change in your earlier version of the patch
when you asked if it should be two patches.

Regards,

Tony