Re: [Intel-gfx] [PATCH 13/26] drm/i915: use the new iterator in i915_gem_busy_ioctl

From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
	linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org,
	linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org
Cc: daniel@ffwll.ch
Subject: Re: [Intel-gfx] [PATCH 13/26] drm/i915: use the new iterator in i915_gem_busy_ioctl
Date: Mon, 20 Sep 2021 12:13:41 +0200	[thread overview]
Message-ID: <368e8495-f4de-cbb2-3584-e022a5937885@gmail.com> (raw)
In-Reply-To: <6fbaca09-ec51-c44e-708c-334ef8be8595@linux.intel.com>

Am 20.09.21 um 10:45 schrieb Tvrtko Ursulin:
>
> On 17/09/2021 13:35, Christian König wrote:
>> This makes the function much simpler since the complex
>> retry logic is now handled else where.
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/gpu/drm/i915/gem/i915_gem_busy.c | 32 ++++++++----------------
>>   1 file changed, 11 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c 
>> b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
>> index 6234e17259c1..b1cb7ba688da 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
>> @@ -82,8 +82,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void 
>> *data,
>>   {
>>       struct drm_i915_gem_busy *args = data;
>>       struct drm_i915_gem_object *obj;
>> -    struct dma_resv_list *list;
>> -    unsigned int seq;
>> +    struct dma_resv_iter cursor;
>> +    struct dma_fence *fence;
>>       int err;
>>         err = -ENOENT;
>> @@ -109,27 +109,17 @@ i915_gem_busy_ioctl(struct drm_device *dev, 
>> void *data,
>>        * to report the overall busyness. This is what the wait-ioctl 
>> does.
>>        *
>>        */
>> -retry:
>> -    seq = raw_read_seqcount(&obj->base.resv->seq);
>> -
>> -    /* Translate the exclusive fence to the READ *and* WRITE engine */
>> -    args->busy = 
>> busy_check_writer(dma_resv_excl_fence(obj->base.resv));
>> -
>> -    /* Translate shared fences to READ set of engines */
>> -    list = dma_resv_shared_list(obj->base.resv);
>> -    if (list) {
>> -        unsigned int shared_count = list->shared_count, i;
>> -
>> -        for (i = 0; i < shared_count; ++i) {
>> -            struct dma_fence *fence =
>> -                rcu_dereference(list->shared[i]);
>> -
>> +    args->busy = false;
>> +    dma_resv_iter_begin(&cursor, obj->base.resv, true);
>> +    dma_resv_for_each_fence_unlocked(&cursor, fence) {
>
> You did not agree with my suggestion to reset args->busy on restart 
> and so preserve current behaviour?

No, I want to keep the restart behavior internally to the dma_resv 
object and as far as I can see it should not make a difference here.

Regards,
Christian.

>
> Regards,
>
> Tvrtko
>
>> +        if (dma_resv_iter_is_exclusive(&cursor))
>> +            /* Translate the exclusive fence to the READ *and* WRITE 
>> engine */
>> +            args->busy = busy_check_writer(fence);
>> +        else
>> +            /* Translate shared fences to READ set of engines */
>>               args->busy |= busy_check_reader(fence);
>> -        }
>>       }
>> -
>> -    if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
>> -        goto retry;
>> +    dma_resv_iter_end(&cursor);
>>         err = 0;
>>   out:
>>