linux-kernel - Re: [PATCH v2] s5p-mfc: Don't try to put pm->clock if lookup failed

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Message-ID: <20160503101509.GB3956@kozik-lap>
Date:	Tue, 3 May 2016 12:15:09 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Javier Martinez Canillas <javier@....samsung.com>
Cc:	linux-kernel@...r.kernel.org,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Kamil Debski <k.debski@...sung.com>,
	Jeongtae Park <jtp.park@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [PATCH v2] s5p-mfc: Don't try to put pm->clock if lookup failed

On Mon, May 02, 2016 at 03:14:22PM -0400, Javier Martinez Canillas wrote:
> Failing to get the struct s5p_mfc_pm .clock is a non-fatal error so the
> clock field can have a errno pointer value. But s5p_mfc_final_pm() only
> checks if .clock is not NULL before attempting to unprepare and put it.
> 
> This leads to the following warning in clk_put() due s5p_mfc_final_pm():
> 
> WARNING: CPU: 3 PID: 1023 at drivers/clk/clk.c:2814 s5p_mfc_final_pm+0x48/0x74 [s5p_mfc]
> CPU: 3 PID: 1023 Comm: rmmod Tainted: G        W       4.6.0-rc6-next-20160502-00005-g5a15a49106bc #9
> Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [<c010e1bc>] (unwind_backtrace) from [<c010af28>] (show_stack+0x10/0x14)
> [<c010af28>] (show_stack) from [<c032485c>] (dump_stack+0x88/0x9c)
> [<c032485c>] (dump_stack) from [<c011b8e8>] (__warn+0xe8/0x100)
> [<c011b8e8>] (__warn) from [<c011b9b0>] (warn_slowpath_null+0x20/0x28)
> [<c011b9b0>] (warn_slowpath_null) from [<bf16004c>] (s5p_mfc_final_pm+0x48/0x74 [s5p_mfc])
> [<bf16004c>] (s5p_mfc_final_pm [s5p_mfc]) from [<bf157414>] (s5p_mfc_remove+0x8c/0x94 [s5p_mfc])
> [<bf157414>] (s5p_mfc_remove [s5p_mfc]) from [<c03fe1f8>] (platform_drv_remove+0x24/0x3c)
> [<c03fe1f8>] (platform_drv_remove) from [<c03fcc70>] (__device_release_driver+0x84/0x110)
> [<c03fcc70>] (__device_release_driver) from [<c03fcdd8>] (driver_detach+0xac/0xb0)
> [<c03fcdd8>] (driver_detach) from [<c03fbff8>] (bus_remove_driver+0x4c/0xa0)
> [<c03fbff8>] (bus_remove_driver) from [<c01886a8>] (SyS_delete_module+0x174/0x1b8)
> [<c01886a8>] (SyS_delete_module) from [<c01078c0>] (ret_fast_syscall+0x0/0x3c)
> 
> Assign the pointer to NULL in case of a lookup failure to fix the issue.
> 
> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
> 
> ---
> 
> Changes in v2:
> - Set the clock pointer to NULL instead of checking for !IS_ERR_OR_NULL().
>   Suggested by Arnd Bergmann.
> 
>  drivers/media/platform/s5p-mfc/s5p_mfc_pm.c | 1 +
>  1 file changed, 1 insertion(+)

This is a fix for bug, so for statistics:
Fixes: d19f405a5a8d ("[media] s5p-mfc: Fix selective sclk_mfc init")

... and although not fatal, but annoying so I think this deserves:
Cc: <stable@...r.kernel.org>

Anyway:
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

Best regards,
Krzysztof