Re: [PATCH 2/5] drm/xe: Add ref counting for xe_file

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Jul 08, 2024 at 04:26:00PM -0700, Umesh Nerlige Ramappa wrote:
> On Mon, Jul 08, 2024 at 05:52:00PM -0500, Lucas De Marchi wrote:
> > On Mon, Jul 08, 2024 at 01:21:00PM GMT, Umesh Nerlige Ramappa wrote:
> > > Add ref counting for xe_file.
> > > 
> > > Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> > > ---
> > > drivers/gpu/drm/xe/xe_device.c       |  7 +++++--
> > > drivers/gpu/drm/xe/xe_device.h       | 12 ++++++++++++
> > > drivers/gpu/drm/xe/xe_device_types.h |  3 +++
> > > 3 files changed, 20 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> > > index babb697652d5..e6eacf1bcce0 100644
> > > --- a/drivers/gpu/drm/xe/xe_device.c
> > > +++ b/drivers/gpu/drm/xe/xe_device.c
> > > @@ -87,11 +87,14 @@ static int xe_file_open(struct drm_device *dev, struct drm_file *file)
> > > 	spin_unlock(&xe->clients.lock);
> > > 
> > > 	file->driver_priv = xef;
> > > +	kref_init(&xef->refcount);
> > > +
> > > 	return 0;
> > > }
> > > 
> > > -static void xe_file_destroy(struct xe_file *xef)
> > > +void xe_file_destroy(struct kref *ref)
> > 
> > why do you export this?  I don't think anybody should be calling
> > xe_file_destroy() directly and this function being executed should only
> > be the outcome of kref being 0. Also, if it's exported, it shouldn't
> > really have struct kref as argument, but rather a struct xe_file
> > 
> > 
> > > {
> > > +	struct xe_file *xef = container_of(ref, struct xe_file, refcount);
> > > 	struct xe_device *xe = xef->xe;
> > > 	struct xe_vm *vm;
> > > 	unsigned long idx;
> > > @@ -130,7 +133,7 @@ static void xe_file_close(struct drm_device *dev, struct drm_file *file)
> > > 		xe_exec_queue_put(q);
> > > 	}
> > > 
> > > -	xe_file_destroy(xef);
> > > +	xe_file_put(xef);
> > > }
> > > 
> > > static const struct drm_ioctl_desc xe_ioctls[] = {
> > > diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
> > > index bb07f5669dbb..2a8b370b1fda 100644
> > > --- a/drivers/gpu/drm/xe/xe_device.h
> > > +++ b/drivers/gpu/drm/xe/xe_device.h
> > > @@ -169,5 +169,17 @@ static inline bool xe_device_wedged(struct xe_device *xe)
> > > }
> > > 
> > > void xe_device_declare_wedged(struct xe_device *xe);
> > > +void xe_file_destroy(struct kref *ref);
> > > +
> > > +static inline struct xe_file *xe_file_get(struct xe_file *xef)
> > > +{
> > > +	kref_get(&xef->refcount);
> > > +	return xef;
> > > +}
> > > +
> > > +static inline void xe_file_put(struct xe_file *xef)
> > 
> > I think if you just make this non-inline, passing file_destroy and
> > leave it in the same place, it should work.
> 
> the put is called from xe_exec_queue.c and xe_vm.c also, so passing the
> destroy may not work.
> 
> Based on the patterns below, xe_file_put/xe_file_get will need to be moved
> to xe_device.c and then exported. It looks cleaner, hoping that'w what you
> mean.
> 
> In xe_device.h:
> 
> void xe_file_put(struct xe_file *xef);
> struct xe_file *xe_file_get(struct xe_file *xef);
> 

My opinion is the way you have it is correct.

Most of Xe is coded this way...

mbrost@lstrano-desk:xe$ grep _get\( *.h | grep inline
xe_bo.h:static inline struct xe_bo *xe_bo_get(struct xe_bo *bo)
xe_device.h:static inline struct xe_file *xe_file_get(struct xe_file *xef)
xe_exec_queue.h:static inline struct xe_exec_queue *xe_exec_queue_get(struct xe_exec_queue *q)
xe_lrc.h:static inline struct xe_lrc *xe_lrc_get(struct xe_lrc *lrc)
xe_sched_job.h:static inline struct xe_sched_job *xe_sched_job_get(struct xe_sched_job *job)
xe_vm.h:static inline struct xe_vm *xe_vm_get(struct xe_vm *vm)

I'm kinda confused by what Lucas is suggesting.

Matt

> Thanks,
> Umesh
> 
> > 
> > Looking for patterns in the kernel for example, see pinctrl_get(),
> > pinctrl_put() and pinctrl_release().... or clk_get(), clk_put(),
> > __clk_release()
> > 
> > Lucas De Marchi
> > 
> > > +{
> > > +	kref_put(&xef->refcount, xe_file_destroy);
> > > +}
> > > 
> > > #endif
> > > diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
> > > index c37be471d11c..ec2b0fb6afe1 100644
> > > --- a/drivers/gpu/drm/xe/xe_device_types.h
> > > +++ b/drivers/gpu/drm/xe/xe_device_types.h
> > > @@ -566,6 +566,9 @@ struct xe_file {
> > > 
> > > 	/** @client: drm client */
> > > 	struct xe_drm_client *client;
> > > +
> > > +	/** @refcount: ref count of this xe file */
> > > +	struct kref refcount;
> > > };
> > > 
> > > #endif
> > > -- 
> > > 2.38.1
> > >