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

mansur
2020-08-25T01:43:52Z

On 2020-08-21 16:29, Stanimir Varbanov wrote:
> 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@codeaurora.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@linaro.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.
>
yes, you can drop. I have validated these patches on top of your
recovery patch
series. I will push V2 with dependency on "venus - recovery from
frimware crash"
series
(https://lore.kernel.org/patchwork/project/lkml/list/?series=455962)

>>
>> 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;
>>>
>>