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

Stanimir Varbanov
2020-09-10T10:44:47Z

Hi Mansur,

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]

I thought more on this issue. I think we have to return error from
hfi_session_init() in the case when the driver is in
system-error-handler. Infact all userspace ioctls must end up with error
while we are in recovery state. What do you think?

> 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(-)
>
> 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);
> 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