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

[Dave Gordon <david.s.gordon@intel.com>]

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 would like to point out that this will be superceded by the Anti-OLR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"

.Dave.
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