linux-kernel - Re: Odroid U3 mutex deadlock.

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Date:	Sat, 2 Jan 2016 10:44:32 +0530
From:	Anand Moon <linux.amoon@...il.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Kukjin Kim <kgene@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: Odroid U3 mutex deadlock.

Hi Krzysztof

On 14 December 2015 at 05:15, Krzysztof Kozlowski
<k.kozlowski@...sung.com> wrote:
> On 12.12.2015 13:32, Anand Moon wrote:
>> Hi Krzysztof,
>>
>> I am just observing this deadlock om my Odroid U3.
>
> This is not a deadlock yet, just a report from lockdep. Could be a real
> issue, could be false positive, maybe some locks miss nesting annotations.
>
> Typical information for bug report would be useful, like the exact
> version (it is mentioned in lockdep report but is it really correct?)
> and reproducibility. And of course git-bisect would be nice to have, see:
> Documentation/BUG-HUNTING
>
> Best regards,
> Krzysztof
>
>
Thanks for your inputs. I narrowed down to this commit.
----------------------------------------------------------------------------------
commit ec459c0c77faca53cf161830cb264e51bb1abba6
Author: Marek Szyprowski <m.szyprowski@...sung.com>
Date:   Wed Feb 4 23:44:15 2015 +0900

    ARM: dts: add dependency between TV and LCD0 power domains for exynos4

    TV Mixer needs both TV and LCD0 domains enabled to be fully operational.
    This dependency is modelled by making TV power domains a sub-domain of
    LCD0 power domain.

    Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
    Signed-off-by: Kukjin Kim <kgene@...nel.org>
-------------------------------------------------------------------------------------
After reverting this I am not observing below lockdep warning report.
But after reverting this patch I observer another bug.

Best regards.
-Anand Moon

>> ------------------------------------------------------------------------------------------------------------------
>>
>> [    2.937531] =============================================
>> [    2.938733] [ INFO: possible recursive locking detected ]
>> [    2.944117] 4.4.0-rc4-xu3s #32 Not tainted
>> [    2.948195] ---------------------------------------------
>> [    2.953577] swapper/0/1 is trying to acquire lock:
>> [    2.958351]  (&genpd->lock){+.+...}, at: [<c0361550>]
>> __genpd_poweron+0x64/0x108
>> [    2.965727]
>> [    2.965727] but task is already holding lock:
>> [    2.971543]  (&genpd->lock){+.+...}, at: [<c0361af8>]
>> genpd_dev_pm_attach+0x168/0x1b8
>> [    2.979355]
>> [    2.979355] other info that might help us debug this:
>> [    2.985865]  Possible unsafe locking scenario:
>> [    2.985865]
>> [    2.991768]        CPU0
>> [    2.994198]        ----
>> [    2.996628]   lock(&genpd->lock);
>> [    2.999926]   lock(&genpd->lock);
>> [    3.003225]
>> [    3.003225]  *** DEADLOCK ***
>> [    3.003225]
>> [    3.009128]  May be due to missing lock nesting notation
>> [    3.009128]
>> [    3.015900] 3 locks held by swapper/0/1:
>> [    3.019804]  #0:  (&dev->mutex){......}, at: [<c0350910>]
>> __driver_attach+0x48/0x98
>> [    3.027442]  #1:  (&dev->mutex){......}, at: [<c0350920>]
>> __driver_attach+0x58/0x98
>> [    3.035081]  #2:  (&genpd->lock){+.+...}, at: [<c0361af8>]
>> genpd_dev_pm_attach+0x168/0x1b8
>> [    3.043326]
>> [    3.043326] stack backtrace:
>> [    3.047671] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.0-rc4-xu3s #32
>> [    3.054351] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
>> [    3.060444] [<c0016c98>] (unwind_backtrace) from [<c00139c4>]
>> (show_stack+0x10/0x14)
>> [    3.068163] [<c00139c4>] (show_stack) from [<c0270df0>]
>> (dump_stack+0x84/0xc4)
>> [    3.075367] [<c0270df0>] (dump_stack) from [<c00780b8>]
>> (__lock_acquire+0x1f88/0x215c)
>> [    3.083262] [<c00780b8>] (__lock_acquire) from [<c007886c>]
>> (lock_acquire+0xa4/0xd0)
>> [    3.090990] [<c007886c>] (lock_acquire) from [<c0641f2c>]
>> (mutex_lock_nested+0x70/0x4d4)
>> [    3.099061] [<c0641f2c>] (mutex_lock_nested) from [<c0361550>]
>> (__genpd_poweron+0x64/0x108)
>> [    3.107393] [<c0361550>] (__genpd_poweron) from [<c0361b00>]
>> (genpd_dev_pm_attach+0x170/0x1b8)
>> [    3.115986] [<c0361b00>] (genpd_dev_pm_attach) from [<c03520a8>]
>> (platform_drv_probe+0x2c/0xac)
>> [    3.124667] [<c03520a8>] (platform_drv_probe) from [<c03507d4>]
>> (driver_probe_device+0x208/0x2fc)
>> [    3.133519] [<c03507d4>] (driver_probe_device) from [<c035095c>]
>> (__driver_attach+0x94/0x98)
>> [    3.141939] [<c035095c>] (__driver_attach) from [<c034ec14>]
>> (bus_for_each_dev+0x68/0x9c)
>> [    3.150097] [<c034ec14>] (bus_for_each_dev) from [<c034fec8>]
>> (bus_add_driver+0x1a0/0x218)
>> [    3.158344] [<c034fec8>] (bus_add_driver) from [<c035115c>]
>> (driver_register+0x78/0xf8)
>> [    3.166330] [<c035115c>] (driver_register) from [<c0338488>]
>> (exynos_drm_register_drivers+0x28/0x74)
>> [    3.175441] [<c0338488>] (exynos_drm_register_drivers) from
>> [<c0338594>] (exynos_drm_init+0x6c/0xc4)
>> [    3.184556] [<c0338594>] (exynos_drm_init) from [<c00097f4>]
>> (do_one_initcall+0x90/0x1dc)
>> [    3.192718] [<c00097f4>] (do_one_initcall) from [<c0895e08>]
>> (kernel_init_freeable+0x158/0x1f8)
>> [    3.201396] [<c0895e08>] (kernel_init_freeable) from [<c063ecac>]
>> (kernel_init+0x8/0xe8)
>> [    3.209469] [<c063ecac>] (kernel_init) from [<c000f7d0>]
>> (ret_from_fork+0x14/0x24)
>> [    3.217932] exynos-hdmi 12d00000.hdmi: GPIO lookup for consumer hpd
>> [    3.223293] exynos-hdmi 12d00000.hdmi: using device tree for GPIO lookup
>> [    3.229980] of_get_named_gpiod_flags: can't parse 'hpd-gpios'
>> property of node '/hdmi@...00000[0]'
>> [    3.238945] of_get_named_gpiod_flags: parsed 'hpd-gpio' property of
>> node '/hdmi@...00000[0]' - status (0)
>> [    3.253430] exynos-drm exynos-drm: bound 12c10000.mixer (ops
>> mixer_component_ops)
>> [    3.256216] exynos-drm exynos-drm: bound 12d00000.hdmi (ops
>> hdmi_component_ops)
>> [    3.263245] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
>> [    3.269812] [drm] No driver support for vblank timestamp query.
>> [    3.323251] exynos-drm exynos-drm: fb0:  frame buffer device
>> [    3.341464] [drm] Initialized exynos 1.0.0 20110530 on minor 0
>>
>> -----------------------------------------------------------------------------------------------------------------------
>> -Anand Moon
>>
>>
>
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