linux-kernel - Re: [BUG] gpu: drm: amd: amdgpu: possible ABBA deadlock in amdgpu_set_power_dpm_force_performance_level() and amdgpu_debugfs_process_reg

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Message-ID: <963eab5f-f333-456e-784c-0d2c81b849da@gmail.com>
Date:   Thu, 9 Dec 2021 11:34:38 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     alexander.deucher@....com, christian.koenig@....com,
        Xinhui.Pan@....com, airlied@...ux.ie, daniel@...ll.ch,
        Hawking.Zhang@....com, Felix.Kuehling@....com, ray.huang@....com,
        lee.jones@...aro.org
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] gpu: drm: amd: amdgpu: possible ABBA deadlock in
 amdgpu_set_power_dpm_force_performance_level() and
 amdgpu_debugfs_process_reg_op()

Hello,

Could you please provide the feedback to my previous report?
Thanks a lot :)


Best wishes,
Jia-Ju Bai

On 2021/9/15 17:39, Jia-Ju Bai wrote:
> Hello,
>
> My static analysis tool reports a possible ABBA deadlock in the amdgpu 
> driver in Linux 5.10:
>
> amdgpu_debugfs_process_reg_op()
>   mutex_lock(&adev->grbm_idx_mutex); --> Line 250 (Lock A)
>   mutex_lock(&adev->pm.mutex); --> Line 259 (Lock B)
>
> amdgpu_set_power_dpm_force_performance_level()
>   mutex_lock(&adev->pm.mutex); --> Line 381 (Lock B)
>     pp_dpm_force_performance_level() --> function pointer via 
> "amdgpu_dpm_force_performance_level()"
>       pp_dpm_en_umd_pstate()
>         amdgpu_device_ip_set_clockgating_state()
>           gfx_v7_0_set_clockgating_state() --> function pointer via 
> "funcs->set_clockgating_state()"
>             gfx_v7_0_enable_mgcg()
>               mutex_lock(&adev->grbm_idx_mutex); --> Line 3646 (Lock A)
>               mutex_lock(&adev->grbm_idx_mutex); --> Line 3697 (Lock A)
>
> When amdgpu_debugfs_process_reg_op() and 
> amdgpu_set_power_dpm_force_performance_level() are concurrently 
> executed, the deadlock can occur.
>
> I am not quite sure whether this possible deadlock is real and how to 
> fix it if it is real.
> Any feedback would be appreciated, thanks :)
>
> Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
>
>
> Best wishes,
> Jia-Ju Bai