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

[Tvrtko Ursulin]

On 11/12/2019 17:13, Venkata Sandeep Dhanalakota wrote:
> On 19/12/11 04:39, Tvrtko Ursulin wrote:
>>
>> On 11/12/2019 16:31, Tvrtko Ursulin wrote:
>>> 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?
>>
>> Actually with two devices you also need to reference count it since you
>> don't want removal of the first device to remove the node but last.
>>
> Apparently this is not called during module exit, using krefs is
> way go to or have some helper which are called during module init/exit.

What is not called? i915_perf_fini? It better be! :)

Regards,

Tvrtko

> 
> void i915_perf_sysctl_register() {
> 	sysctl_header = register_sysctl_table(dev_root);
> }
> 
> void i915_perf_sysctl_unregister() {
> 	unregister_sysctl_table(sysctl_header);
> }
> 
> 
>>> 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
>>>>
>