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

From: mansur@codeaurora.org
To: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, vgarodia@codeaurora.org
Subject: Re: [PATCH v2 2/3] venus: core: cancel pending work items in workqueue
Date: Thu, 17 Sep 2020 07:23:16 +0530	[thread overview]
Message-ID: <51eeedbe7e84ce67e8d5b3f9fd3a7a2e@codeaurora.org> (raw)
In-Reply-To: <a96d7cce-2781-e3d6-6238-8fec411511a1@linaro.org>

On 2020-09-11 15:52, Stanimir Varbanov wrote:
> 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
> 
Yes, this patch is not needed any more. rebased and posted new version
https://lore.kernel.org/patchwork/project/lkml/list/?series=463091

>>  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@codeaurora.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);
>>