linux-kernel - Re: [RESEND 1/3] venus: core: handle race condititon for core ops

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Date:   Fri, 21 Aug 2020 13:59:15 +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: [RESEND 1/3] venus: core: handle race condititon for core ops

Hi Mansur,

On 8/10/20 12:50 PM, Stanimir Varbanov wrote:
> Hi Mansur,
> 
> Thanks for the patches!
> 
> On 8/7/20 9:24 AM, Mansur Alisha Shaik wrote:
>> For core ops we are having only write protect but there
>> is no read protect, because of this in multthreading
>> and concurrency, one CPU core is reading without wait
>> which is causing the NULL pointer dereferece crash.
>>
>> one such scenario is as show below, where in one
>> core core->ops becoming NULL and in another core
>> calling core->ops->session_init().
>>
>> CPU: core-7:
>> Call trace:
>>  hfi_session_init+0x180/0x1dc [venus_core]
>>  vdec_queue_setup+0x9c/0x364 [venus_dec]
>>  vb2_core_reqbufs+0x1e4/0x368 [videobuf2_common]
>>  vb2_reqbufs+0x4c/0x64 [videobuf2_v4l2]
>>  v4l2_m2m_reqbufs+0x50/0x84 [v4l2_mem2mem]
>>  v4l2_m2m_ioctl_reqbufs+0x2c/0x38 [v4l2_mem2mem]
>>  v4l_reqbufs+0x4c/0x5c
>> __video_do_ioctl+0x2b0/0x39c
>>
>> CPU: core-0:
>> Call trace:
>>  venus_shutdown+0x98/0xfc [venus_core]
>>  venus_sys_error_handler+0x64/0x148 [venus_core]
>>  process_one_work+0x210/0x3d0
>>  worker_thread+0x248/0x3f4
>>  kthread+0x11c/0x12c
>>
>> Signed-off-by: Mansur Alisha Shaik <mansur@...eaurora.org>
>> ---
>>  drivers/media/platform/qcom/venus/core.c | 2 +-
>>  drivers/media/platform/qcom/venus/hfi.c  | 5 ++++-
>>  2 files changed, 5 insertions(+), 2 deletions(-)

See below comment, otherwise:

Acked-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>

>>
>> diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
>> index 203c653..fe99c83 100644
>> --- a/drivers/media/platform/qcom/venus/core.c
>> +++ b/drivers/media/platform/qcom/venus/core.c
>> @@ -64,8 +64,8 @@ static void venus_sys_error_handler(struct work_struct *work)
>>  	pm_runtime_get_sync(core->dev);
>>  
>>  	hfi_core_deinit(core, true);
>> -	hfi_destroy(core);
>>  	mutex_lock(&core->lock);
>> +	hfi_destroy(core);
> 
> As my recovery fixes [1] touches this part also, could you please apply
> them on top of yours and re-test?

I'll drop above chunk from the patch because it is already taken into
account in my recovery fixes series and queue up the patch for v5.10.

> 
> Otherwise this patch looks good to me.
> 
> [1] https://www.spinics.net/lists/linux-arm-msm/msg70092.html
> 
>>  	venus_shutdown(core);
>>  
>>  	pm_runtime_put_sync(core->dev);
>> diff --git a/drivers/media/platform/qcom/venus/hfi.c b/drivers/media/platform/qcom/venus/hfi.c
>> index a211eb9..2eeb31f 100644
>> --- a/drivers/media/platform/qcom/venus/hfi.c
>> +++ b/drivers/media/platform/qcom/venus/hfi.c
>> @@ -195,7 +195,7 @@ EXPORT_SYMBOL_GPL(hfi_session_create);
>>  int hfi_session_init(struct venus_inst *inst, u32 pixfmt)
>>  {
>>  	struct venus_core *core = inst->core;
>> -	const struct hfi_ops *ops = core->ops;
>> +	const struct hfi_ops *ops;
>>  	int ret;
>>  
>>  	if (inst->state != INST_UNINIT)
>> @@ -204,10 +204,13 @@ int hfi_session_init(struct venus_inst *inst, u32 pixfmt)
>>  	inst->hfi_codec = to_codec_type(pixfmt);
>>  	reinit_completion(&inst->done);
>>  
>> +	mutex_lock(&core->lock);
>> +	ops = core->ops;
>>  	ret = ops->session_init(inst, inst->session_type, inst->hfi_codec);
>>  	if (ret)
>>  		return ret;
>>  
>> +	mutex_unlock(&core->lock);
>>  	ret = wait_session_msg(inst);
>>  	if (ret)
>>  		return ret;
>>
> 

-- 
regards,
Stan