[Intel-gfx] [PATCH 1/2] drm/i915/perf: Register sysctl path globally

[Tvrtko Ursulin]

On 11/12/2019 16:07, Venkata Sandeep Dhanalakota wrote:
> We do not require to register the sysctl paths per instance,
> so making registration global.
> 
> Cc: Sudeep Dutt <sudeep.dutt at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_perf.c       | 10 ++++++++--
>   drivers/gpu/drm/i915/i915_perf_types.h |  1 -
>   2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 8d2e37949f46..426d04214a5d 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -387,6 +387,8 @@ struct i915_oa_config_bo {
>   	struct i915_vma *vma;
>   };
>   
> +static struct ctl_table_header *sysctl_header;
> +
>   static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer);
>   
>   void i915_oa_config_release(struct kref *ref)
> @@ -4345,7 +4347,8 @@ void i915_perf_init(struct drm_i915_private *i915)
>   
>   		oa_sample_rate_hard_limit = 1000 *
>   			(RUNTIME_INFO(i915)->cs_timestamp_frequency_khz / 2);
> -		perf->sysctl_header = register_sysctl_table(dev_root);
> +		if (!sysctl_header)
> +			sysctl_header = register_sysctl_table(dev_root);
>   
>   		mutex_init(&perf->metrics_lock);
>   		idr_init(&perf->metrics_idr);
> @@ -4395,7 +4398,10 @@ void i915_perf_fini(struct drm_i915_private *i915)
>   	idr_for_each(&perf->metrics_idr, destroy_config, perf);
>   	idr_destroy(&perf->metrics_idr);
>   
> -	unregister_sysctl_table(perf->sysctl_header);
> +	if (sysctl_header) {
> +		unregister_sysctl_table(sysctl_header);
> +		sysctl_header = NULL;
> +	}

I am not sure if this could be racy with manual unbind from sysfs. Does 
PCI core serialize for us?

Regards,

Tvrtko

>   
>   	memset(&perf->ops, 0, sizeof(perf->ops));
>   	perf->i915 = NULL;
> diff --git a/drivers/gpu/drm/i915/i915_perf_types.h b/drivers/gpu/drm/i915/i915_perf_types.h
> index 74ddc20a0d37..45e581455f5d 100644
> --- a/drivers/gpu/drm/i915/i915_perf_types.h
> +++ b/drivers/gpu/drm/i915/i915_perf_types.h
> @@ -380,7 +380,6 @@ struct i915_perf {
>   	struct drm_i915_private *i915;
>   
>   	struct kobject *metrics_kobj;
> -	struct ctl_table_header *sysctl_header;
>   
>   	/*
>   	 * Lock associated with adding/modifying/removing OA configs
>