linux-kernel - Re: [PATCH v2 2/3] venus: core: cancel pending work items in workqueue

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Message-ID: <a96d7cce-2781-e3d6-6238-8fec411511a1@linaro.org>
Date:   Fri, 11 Sep 2020 13:22:10 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Mansur Alisha Shaik <mansur@...eaurora.org>,
        linux-media@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        vgarodia@...eaurora.org
Subject: Re: [PATCH v2 2/3] venus: core: cancel pending work items in
 workqueue

Hi,

On 9/10/20 3:44 PM, Mansur Alisha Shaik wrote:
> In concurrency usecase and reboot scenario we are
> observing race condition and seeing NULL pointer
> dereference crash. In shutdown path and system
> recovery path we are destroying the same mutex
> hence seeing crash.
> 
> This case is handled by mutex protection and
> cancel delayed work items in work queue.
> 
> Below is the call trace for the crash
> Call trace:
>  venus_remove+0xdc/0xec [venus_core]
>  venus_core_shutdown+0x1c/0x34 [venus_core]
>  platform_drv_shutdown+0x28/0x34
>  device_shutdown+0x154/0x1fc
>  kernel_restart_prepare+0x40/0x4c
>  kernel_restart+0x1c/0x64
> 
> Call trace:
>  mutex_lock+0x34/0x60
>  venus_hfi_destroy+0x28/0x98 [venus_core]
>  hfi_destroy+0x1c/0x28 [venus_core]

I queued up [1] and after it this cannot happen anymore because
hfi_destroy() is not called by venus_sys_error_handler().

So I guess this patch is not needed anymore.

[1] https://www.spinics.net/lists/linux-arm-msm/msg70092.html

>  venus_sys_error_handler+0x60/0x14c [venus_core]
>  process_one_work+0x210/0x3d0
>  worker_thread+0x248/0x3f4
>  kthread+0x11c/0x12c
>  ret_from_fork+0x10/0x18
> 
> Signed-off-by: Mansur Alisha Shaik <mansur@...eaurora.org>
> ---
>  drivers/media/platform/qcom/venus/core.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
> index c5af428..69aa199 100644
> --- a/drivers/media/platform/qcom/venus/core.c
> +++ b/drivers/media/platform/qcom/venus/core.c
> @@ -323,6 +323,8 @@ static int venus_remove(struct platform_device *pdev)
>  	struct device *dev = core->dev;
>  	int ret;
>  
> +	cancel_delayed_work_sync(&core->work);
> +
>  	ret = pm_runtime_get_sync(dev);
>  	WARN_ON(ret < 0);
>  
> @@ -340,7 +342,9 @@ static int venus_remove(struct platform_device *pdev)
>  	if (pm_ops->core_put)
>  		pm_ops->core_put(dev);
>  
> +	mutex_lock(&core->lock);
>  	hfi_destroy(core);
> +	mutex_unlock(&core->lock);
>  
>  	icc_put(core->video_path);
>  	icc_put(core->cpucfg_path);
> 

-- 
regards,
Stan