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

[mansur]

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@xxxxxxxxxxxxxx>
> > > ---
> > >  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@xxxxxxxxxx>
>
> > > 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;