Re: [PATCH] drm/i915: Preallocate request before access of the ring

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 29 Jun 2015, Dave Gordon <david.s.gordon@intel.com> wrote:
> On 29/06/15 12:39, Jani Nikula wrote:
>> On Wed, 06 May 2015, Daniel Vetter <daniel@ffwll.ch> wrote:
>>> On Thu, Apr 30, 2015 at 01:54:41PM +0100, Dave Gordon wrote:
>>>> On 29/04/15 17:10, yu.dai@intel.com wrote:
>>>>> From: Alex Dai <yu.dai@intel.com>
>>>>>
>>>>> This is to avoid bad IO access caused by writing NOOP to wrap the
>>>>> ring buffer whilst ring is unpinned.
>>>>>
>>>>> Signed-off-by: Alex Dai <yu.dai@intel.com>
>>>>> ---
>>>>>  drivers/gpu/drm/i915/intel_lrc.c | 6 +++---
>>>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>>>>> index 732fd63..3e8fcfd 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>>>>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>>>>> @@ -803,12 +803,12 @@ static int intel_logical_ring_begin(struct intel_ringbuffer *ringbuf,
>>>>>  	if (ret)
>>>>>  		return ret;
>>>>>  
>>>>> -	ret = logical_ring_prepare(ringbuf, ctx, num_dwords * sizeof(uint32_t));
>>>>> +	/* Preallocate the olr before touching the ring */
>>>>> +	ret = i915_gem_request_alloc(ring, ctx);
>>>>>  	if (ret)
>>>>>  		return ret;
>>>>>  
>>>>> -	/* Preallocate the olr before touching the ring */
>>>>> -	ret = i915_gem_request_alloc(ring, ctx);
>>>>> +	ret = logical_ring_prepare(ringbuf, ctx, num_dwords * sizeof(uint32_t));
>>>>>  	if (ret)
>>>>>  		return ret;
>>>>
>>>> Reviewed-by: Dave Gordon <david.s.gordon@intel.com>
>>>> with input also from John Harrison <john.c.harrison@intel.com>, who
>>>> would like to point out that this will be superceded by the Anti-OLR
>>>> patches already posted. (In that model, the request will be allocated
>>>> much earlier, and passed around explicitly rather than dangling from the
>>>> context).
>>>
>>> Do we need this for execlist in general, i.e. cc: stable? Where's the bug
>>> report/igt testcase?
>>>
>>> For serious-looking bugs please add more details like that to the commit
>>> message, otherwise maintainers have no idea where to apply a patch.
>> 
>> And due to no reply, the maintainers have forgotten about patches like
>> this. Dropping from my fixes queue.
>> 
>> BR,
>> Jani.
>
> This became obsolete with the merge of John Harrison's patchset
> 	"Remove the outstanding_lazy_request"

Thanks.

BR,
Jani.


>
> .Dave.

-- 
Jani Nikula, Intel Open Source Technology Center
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