Re: [Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
On 22/04/16 23:57, John Harrison wrote: On 21/04/2016 14:04, John Harrison wrote: On 19/04/2016 13:35, Dave Gordon wrote: On 13/04/16 15:21, John Harrison wrote: On 13/04/2016 10:57, Daniel Vetter wrote: On Tue, Apr 12, 2016 at 09:03:09PM +0100, Chris Wilson wrote: Conceptually, each request is a record of a hardware transaction - we build up a list of pending commands and then either commit them to hardware, or cancel them. However, whilst building up the list of pending commands, we may modify state outside of the request and make references to the pending request. If we do so and then cancel that request, external objects then point to the deleted request leading to both graphical and memory corruption. The easiest example is to consider object/VMA tracking. When we mark an object as active in a request, we store a pointer to this, the most recent request, in the object. Then we want to free that object, we wait for the most recent request to be idle before proceeding (otherwise the hardware will write to pages now owned by the system, or we will attempt to read from those pages before the hardware is finished writing). If the request was cancelled instead, that wait completes immediately. As a result, all requests must be committed and not cancelled if the external state is unknown. All that remains of i915_gem_request_cancel() users are just a couple of extremely unlikely allocation failures, so remove the API entirely. A consequence of committing all incomplete requests is that we generate excess breadcrumbs and fill the ring much more often with dummy work. We have completely undone the outstanding_last_seqno optimisation. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907 Signed-off-by: Chris Wilson Cc: Daniel Vetter Cc: Tvrtko Ursulin Cc: sta...@vger.kernel.org Cc: John Harrison I'd like John's ack on this on too, but patch itself looks sound. Fast r-b since we've discussed this a while ago already ... I think this is going to cause a problem with the scheduler. You are effectively saying that the execbuf call cannot fail beyond the point of allocating a request. If it gets that far then it must go all the way and submit the request to the hardware. With a scheduler, that means adding it to the scheduler's queues and tracking it all the way through the system to completion. If nothing else, that sounds like a lot of extra overhead for no actual work. Or worse if the failure is at a point where the request cannot be sent further through the system because it was something critical that failed then you are really stuffed. I'm not sure what the other option would be though, short of being able to undo the last read/write object tracking updates. With the chained-ownership code we have in the scheduler, it becomes perfectly possible to undo the last-read/write tracking changes. I'd much rather see any failure during submission rewound and undone, so we can just return -EAGAIN at any point and let someone retry if required. This just looks like a hack to work around not having a properly transactional model of request submission :( .Dave. I was thinking if it would be possible to delay the tracking updates until later in the execbuf process. I.e. only do it after all potential failure points. That would be a much simpler change than putting in chained ownership. However, it seems that the patch has already been merged despite this discussion and Daniel Vetter wanting an ack first? Is that correct? John. Dave Gordon and myself had a look at the option of delaying the object tracking until beyond the point of last possible failure in the execbuf call path. As far as we can tell, it already is. The object tracking update occurs in i915_gem_execbuffer_move_to_active(). That function cannot return a failure code and is immediately followed (in both LRC and legacy mode) by a call to i915_gem_execbuffer_retire_commands() which is what flushes out the request to the hardware. So it would appear that this patch has no effect on object tracking within the execbuf code path. If a request cancellation code path was taken then the tracking would not have been updated and so the request is irrelevant as it has no references to it. If the tracking was updated and the request is being referenced then the request was also guaranteed to have been submitted and not cancelled. Either we are missing something major somewhere or this patch cannot fix the stated bug in the stated manner? I have tried running the failing test myself but when I try to run the particular gem_concurrent_blit subtest it tells me that it requires more 'objects' and/or RAM than I have available. What does one need in order to run the test? The bug report also does not say whether it is a guaranteed failure every time or a sporadic, once in X many runs kind of failure? Thanks, John. Maybe it's not a cancelled request at all, but a race where submission HAS been successful, and the object tracking HAS be
Re: [Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
On 21/04/2016 14:04, John Harrison wrote: On 19/04/2016 13:35, Dave Gordon wrote: On 13/04/16 15:21, John Harrison wrote: On 13/04/2016 10:57, Daniel Vetter wrote: On Tue, Apr 12, 2016 at 09:03:09PM +0100, Chris Wilson wrote: Conceptually, each request is a record of a hardware transaction - we build up a list of pending commands and then either commit them to hardware, or cancel them. However, whilst building up the list of pending commands, we may modify state outside of the request and make references to the pending request. If we do so and then cancel that request, external objects then point to the deleted request leading to both graphical and memory corruption. The easiest example is to consider object/VMA tracking. When we mark an object as active in a request, we store a pointer to this, the most recent request, in the object. Then we want to free that object, we wait for the most recent request to be idle before proceeding (otherwise the hardware will write to pages now owned by the system, or we will attempt to read from those pages before the hardware is finished writing). If the request was cancelled instead, that wait completes immediately. As a result, all requests must be committed and not cancelled if the external state is unknown. All that remains of i915_gem_request_cancel() users are just a couple of extremely unlikely allocation failures, so remove the API entirely. A consequence of committing all incomplete requests is that we generate excess breadcrumbs and fill the ring much more often with dummy work. We have completely undone the outstanding_last_seqno optimisation. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907 Signed-off-by: Chris Wilson Cc: Daniel Vetter Cc: Tvrtko Ursulin Cc: sta...@vger.kernel.org Cc: John Harrison I'd like John's ack on this on too, but patch itself looks sound. Fast r-b since we've discussed this a while ago already ... I think this is going to cause a problem with the scheduler. You are effectively saying that the execbuf call cannot fail beyond the point of allocating a request. If it gets that far then it must go all the way and submit the request to the hardware. With a scheduler, that means adding it to the scheduler's queues and tracking it all the way through the system to completion. If nothing else, that sounds like a lot of extra overhead for no actual work. Or worse if the failure is at a point where the request cannot be sent further through the system because it was something critical that failed then you are really stuffed. I'm not sure what the other option would be though, short of being able to undo the last read/write object tracking updates. With the chained-ownership code we have in the scheduler, it becomes perfectly possible to undo the last-read/write tracking changes. I'd much rather see any failure during submission rewound and undone, so we can just return -EAGAIN at any point and let someone retry if required. This just looks like a hack to work around not having a properly transactional model of request submission :( .Dave. I was thinking if it would be possible to delay the tracking updates until later in the execbuf process. I.e. only do it after all potential failure points. That would be a much simpler change than putting in chained ownership. However, it seems that the patch has already been merged despite this discussion and Daniel Vetter wanting an ack first? Is that correct? John. Dave Gordon and myself had a look at the option of delaying the object tracking until beyond the point of last possible failure in the execbuf call path. As far as we can tell, it already is. The object tracking update occurs in i915_gem_execbuffer_move_to_active(). That function cannot return a failure code and is immediately followed (in both LRC and legacy mode) by a call to i915_gem_execbuffer_retire_commands() which is what flushes out the request to the hardware. So it would appear that this patch has no effect on object tracking within the execbuf code path. If a request cancellation code path was taken then the tracking would not have been updated and so the request is irrelevant as it has no references to it. If the tracking was updated and the request is being referenced then the request was also guaranteed to have been submitted and not cancelled. Either we are missing something major somewhere or this patch cannot fix the stated bug in the stated manner? I have tried running the failing test myself but when I try to run the particular gem_concurrent_blit subtest it tells me that it requires more 'objects' and/or RAM than I have available. What does one need in order to run the test? The bug report also does not say whether it is a guaranteed failure every time or a sporadic, once in X many runs kind of failure? Thanks, John. ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https:/
Re: [Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
On 19/04/2016 13:35, Dave Gordon wrote: On 13/04/16 15:21, John Harrison wrote: On 13/04/2016 10:57, Daniel Vetter wrote: On Tue, Apr 12, 2016 at 09:03:09PM +0100, Chris Wilson wrote: Conceptually, each request is a record of a hardware transaction - we build up a list of pending commands and then either commit them to hardware, or cancel them. However, whilst building up the list of pending commands, we may modify state outside of the request and make references to the pending request. If we do so and then cancel that request, external objects then point to the deleted request leading to both graphical and memory corruption. The easiest example is to consider object/VMA tracking. When we mark an object as active in a request, we store a pointer to this, the most recent request, in the object. Then we want to free that object, we wait for the most recent request to be idle before proceeding (otherwise the hardware will write to pages now owned by the system, or we will attempt to read from those pages before the hardware is finished writing). If the request was cancelled instead, that wait completes immediately. As a result, all requests must be committed and not cancelled if the external state is unknown. All that remains of i915_gem_request_cancel() users are just a couple of extremely unlikely allocation failures, so remove the API entirely. A consequence of committing all incomplete requests is that we generate excess breadcrumbs and fill the ring much more often with dummy work. We have completely undone the outstanding_last_seqno optimisation. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907 Signed-off-by: Chris Wilson Cc: Daniel Vetter Cc: Tvrtko Ursulin Cc: sta...@vger.kernel.org Cc: John Harrison I'd like John's ack on this on too, but patch itself looks sound. Fast r-b since we've discussed this a while ago already ... I think this is going to cause a problem with the scheduler. You are effectively saying that the execbuf call cannot fail beyond the point of allocating a request. If it gets that far then it must go all the way and submit the request to the hardware. With a scheduler, that means adding it to the scheduler's queues and tracking it all the way through the system to completion. If nothing else, that sounds like a lot of extra overhead for no actual work. Or worse if the failure is at a point where the request cannot be sent further through the system because it was something critical that failed then you are really stuffed. I'm not sure what the other option would be though, short of being able to undo the last read/write object tracking updates. With the chained-ownership code we have in the scheduler, it becomes perfectly possible to undo the last-read/write tracking changes. I'd much rather see any failure during submission rewound and undone, so we can just return -EAGAIN at any point and let someone retry if required. This just looks like a hack to work around not having a properly transactional model of request submission :( .Dave. I was thinking if it would be possible to delay the tracking updates until later in the execbuf process. I.e. only do it after all potential failure points. That would be a much simpler change than putting in chained ownership. However, it seems that the patch has already been merged despite this discussion and Daniel Vetter wanting an ack first? Is that correct? John. ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
On 13/04/16 15:21, John Harrison wrote: On 13/04/2016 10:57, Daniel Vetter wrote: On Tue, Apr 12, 2016 at 09:03:09PM +0100, Chris Wilson wrote: Conceptually, each request is a record of a hardware transaction - we build up a list of pending commands and then either commit them to hardware, or cancel them. However, whilst building up the list of pending commands, we may modify state outside of the request and make references to the pending request. If we do so and then cancel that request, external objects then point to the deleted request leading to both graphical and memory corruption. The easiest example is to consider object/VMA tracking. When we mark an object as active in a request, we store a pointer to this, the most recent request, in the object. Then we want to free that object, we wait for the most recent request to be idle before proceeding (otherwise the hardware will write to pages now owned by the system, or we will attempt to read from those pages before the hardware is finished writing). If the request was cancelled instead, that wait completes immediately. As a result, all requests must be committed and not cancelled if the external state is unknown. All that remains of i915_gem_request_cancel() users are just a couple of extremely unlikely allocation failures, so remove the API entirely. A consequence of committing all incomplete requests is that we generate excess breadcrumbs and fill the ring much more often with dummy work. We have completely undone the outstanding_last_seqno optimisation. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907 Signed-off-by: Chris Wilson Cc: Daniel Vetter Cc: Tvrtko Ursulin Cc: sta...@vger.kernel.org Cc: John Harrison I'd like John's ack on this on too, but patch itself looks sound. Fast r-b since we've discussed this a while ago already ... I think this is going to cause a problem with the scheduler. You are effectively saying that the execbuf call cannot fail beyond the point of allocating a request. If it gets that far then it must go all the way and submit the request to the hardware. With a scheduler, that means adding it to the scheduler's queues and tracking it all the way through the system to completion. If nothing else, that sounds like a lot of extra overhead for no actual work. Or worse if the failure is at a point where the request cannot be sent further through the system because it was something critical that failed then you are really stuffed. I'm not sure what the other option would be though, short of being able to undo the last read/write object tracking updates. With the chained-ownership code we have in the scheduler, it becomes perfectly possible to undo the last-read/write tracking changes. I'd much rather see any failure during submission rewound and undone, so we can just return -EAGAIN at any point and let someone retry if required. This just looks like a hack to work around not having a properly transactional model of request submission :( .Dave. ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
On Wed, 13 Apr 2016, Daniel Vetter wrote:
> On Tue, Apr 12, 2016 at 09:03:09PM +0100, Chris Wilson wrote:
>> Conceptually, each request is a record of a hardware transaction - we
>> build up a list of pending commands and then either commit them to
>> hardware, or cancel them. However, whilst building up the list of
>> pending commands, we may modify state outside of the request and make
>> references to the pending request. If we do so and then cancel that
>> request, external objects then point to the deleted request leading to
>> both graphical and memory corruption.
>>
>> The easiest example is to consider object/VMA tracking. When we mark an
>> object as active in a request, we store a pointer to this, the most
>> recent request, in the object. Then we want to free that object, we wait
>> for the most recent request to be idle before proceeding (otherwise the
>> hardware will write to pages now owned by the system, or we will attempt
>> to read from those pages before the hardware is finished writing). If
>> the request was cancelled instead, that wait completes immediately. As a
>> result, all requests must be committed and not cancelled if the external
>> state is unknown.
>>
>> All that remains of i915_gem_request_cancel() users are just a couple of
>> extremely unlikely allocation failures, so remove the API entirely.
>>
>> A consequence of committing all incomplete requests is that we generate
>> excess breadcrumbs and fill the ring much more often with dummy work. We
>> have completely undone the outstanding_last_seqno optimisation.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907
>> Signed-off-by: Chris Wilson
>> Cc: Daniel Vetter
>> Cc: Tvrtko Ursulin
>> Cc: sta...@vger.kernel.org
>
> Cc: John Harrison
>
> I'd like John's ack on this on too, but patch itself looks sound. Fast r-b
> since we've discussed this a while ago already ...
>
> Reviewed-by: Daniel Vetter
FYI, this (*) does not cherry-pick cleanly to drm-intel-fixes.
BR,
Jani.
(*) Well, not exactly *this* but rather
https://patchwork.freedesktop.org/patch/80961/ which was not posted on
the list so I can't reply to it.
>> ---
>> drivers/gpu/drm/i915/i915_drv.h| 2 --
>> drivers/gpu/drm/i915/i915_gem.c| 50
>> --
>> drivers/gpu/drm/i915/i915_gem_execbuffer.c | 15 +++--
>> drivers/gpu/drm/i915/intel_display.c | 2 +-
>> drivers/gpu/drm/i915/intel_lrc.c | 4 +--
>> drivers/gpu/drm/i915/intel_overlay.c | 8 ++---
>> 6 files changed, 30 insertions(+), 51 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h
>> b/drivers/gpu/drm/i915/i915_drv.h
>> index 061ecc43d935..de84dd7be971 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -2331,7 +2331,6 @@ struct drm_i915_gem_request {
>> struct drm_i915_gem_request * __must_check
>> i915_gem_request_alloc(struct intel_engine_cs *engine,
>> struct intel_context *ctx);
>> -void i915_gem_request_cancel(struct drm_i915_gem_request *req);
>> void i915_gem_request_free(struct kref *req_ref);
>> int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
>> struct drm_file *file);
>> @@ -2883,7 +2882,6 @@ int i915_gem_sw_finish_ioctl(struct drm_device *dev,
>> void *data,
>> struct drm_file *file_priv);
>> void i915_gem_execbuffer_move_to_active(struct list_head *vmas,
>> struct drm_i915_gem_request *req);
>> -void i915_gem_execbuffer_retire_commands(struct i915_execbuffer_params
>> *params);
>> int i915_gem_ringbuffer_submission(struct i915_execbuffer_params *params,
>> struct drm_i915_gem_execbuffer2 *args,
>> struct list_head *vmas);
>> diff --git a/drivers/gpu/drm/i915/i915_gem.c
>> b/drivers/gpu/drm/i915/i915_gem.c
>> index b6879d43dd74..c6f09e7839ea 100644
>> --- a/drivers/gpu/drm/i915/i915_gem.c
>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>> @@ -2785,7 +2785,8 @@ __i915_gem_request_alloc(struct intel_engine_cs
>> *engine,
>> * fully prepared. Thus it can be cleaned up using the proper
>> * free code.
>> */
>> -i915_gem_request_cancel(req);
>> +intel_ring_reserved_space_cancel(req->ringbuf);
>> +i915_gem_request_unreference(req);
>> return ret;
>> }
>>
>> @@ -2822,13 +2823,6 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
>> return err ? ERR_PTR(err) : req;
>> }
>>
>> -void i915_gem_request_cancel(struct drm_i915_gem_request *req)
>> -{
>> -intel_ring_reserved_space_cancel(req->ringbuf);
>> -
>> -i915_gem_request_unreference(req);
>> -}
>> -
>> struct drm_i915_gem_request *
>> i915_gem_find_active_request(struct intel_engine_cs *engine)
>> {
>> @@ -3438,12 +3432,9 @@ int i915_gpu_idle(struct drm_device *dev)
>>
Re: [Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
On 13/04/2016 10:57, Daniel Vetter wrote:
On Tue, Apr 12, 2016 at 09:03:09PM +0100, Chris Wilson wrote:
Conceptually, each request is a record of a hardware transaction - we
build up a list of pending commands and then either commit them to
hardware, or cancel them. However, whilst building up the list of
pending commands, we may modify state outside of the request and make
references to the pending request. If we do so and then cancel that
request, external objects then point to the deleted request leading to
both graphical and memory corruption.
The easiest example is to consider object/VMA tracking. When we mark an
object as active in a request, we store a pointer to this, the most
recent request, in the object. Then we want to free that object, we wait
for the most recent request to be idle before proceeding (otherwise the
hardware will write to pages now owned by the system, or we will attempt
to read from those pages before the hardware is finished writing). If
the request was cancelled instead, that wait completes immediately. As a
result, all requests must be committed and not cancelled if the external
state is unknown.
All that remains of i915_gem_request_cancel() users are just a couple of
extremely unlikely allocation failures, so remove the API entirely.
A consequence of committing all incomplete requests is that we generate
excess breadcrumbs and fill the ring much more often with dummy work. We
have completely undone the outstanding_last_seqno optimisation.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907
Signed-off-by: Chris Wilson
Cc: Daniel Vetter
Cc: Tvrtko Ursulin
Cc: sta...@vger.kernel.org
Cc: John Harrison
I'd like John's ack on this on too, but patch itself looks sound. Fast r-b
since we've discussed this a while ago already ...
I think this is going to cause a problem with the scheduler. You are
effectively saying that the execbuf call cannot fail beyond the point of
allocating a request. If it gets that far then it must go all the way
and submit the request to the hardware. With a scheduler, that means
adding it to the scheduler's queues and tracking it all the way through
the system to completion. If nothing else, that sounds like a lot of
extra overhead for no actual work. Or worse if the failure is at a point
where the request cannot be sent further through the system because it
was something critical that failed then you are really stuffed.
I'm not sure what the other option would be though, short of being able
to undo the last read/write object tracking updates.
Reviewed-by: Daniel Vetter
---
drivers/gpu/drm/i915/i915_drv.h| 2 --
drivers/gpu/drm/i915/i915_gem.c| 50 --
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 15 +++--
drivers/gpu/drm/i915/intel_display.c | 2 +-
drivers/gpu/drm/i915/intel_lrc.c | 4 +--
drivers/gpu/drm/i915/intel_overlay.c | 8 ++---
6 files changed, 30 insertions(+), 51 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 061ecc43d935..de84dd7be971 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2331,7 +2331,6 @@ struct drm_i915_gem_request {
struct drm_i915_gem_request * __must_check
i915_gem_request_alloc(struct intel_engine_cs *engine,
struct intel_context *ctx);
-void i915_gem_request_cancel(struct drm_i915_gem_request *req);
void i915_gem_request_free(struct kref *req_ref);
int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
struct drm_file *file);
@@ -2883,7 +2882,6 @@ int i915_gem_sw_finish_ioctl(struct drm_device *dev, void
*data,
struct drm_file *file_priv);
void i915_gem_execbuffer_move_to_active(struct list_head *vmas,
struct drm_i915_gem_request *req);
-void i915_gem_execbuffer_retire_commands(struct i915_execbuffer_params
*params);
int i915_gem_ringbuffer_submission(struct i915_execbuffer_params *params,
struct drm_i915_gem_execbuffer2 *args,
struct list_head *vmas);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b6879d43dd74..c6f09e7839ea 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2785,7 +2785,8 @@ __i915_gem_request_alloc(struct intel_engine_cs *engine,
* fully prepared. Thus it can be cleaned up using the proper
* free code.
*/
- i915_gem_request_cancel(req);
+ intel_ring_reserved_space_cancel(req->ringbuf);
+ i915_gem_request_unreference(req);
return ret;
}
@@ -2822,13 +2823,6 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
return err ? ERR_PTR(err) : req;
}
-void i915_gem_req
Re: [Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
On Tue, Apr 12, 2016 at 09:03:09PM +0100, Chris Wilson wrote:
> Conceptually, each request is a record of a hardware transaction - we
> build up a list of pending commands and then either commit them to
> hardware, or cancel them. However, whilst building up the list of
> pending commands, we may modify state outside of the request and make
> references to the pending request. If we do so and then cancel that
> request, external objects then point to the deleted request leading to
> both graphical and memory corruption.
>
> The easiest example is to consider object/VMA tracking. When we mark an
> object as active in a request, we store a pointer to this, the most
> recent request, in the object. Then we want to free that object, we wait
> for the most recent request to be idle before proceeding (otherwise the
> hardware will write to pages now owned by the system, or we will attempt
> to read from those pages before the hardware is finished writing). If
> the request was cancelled instead, that wait completes immediately. As a
> result, all requests must be committed and not cancelled if the external
> state is unknown.
>
> All that remains of i915_gem_request_cancel() users are just a couple of
> extremely unlikely allocation failures, so remove the API entirely.
>
> A consequence of committing all incomplete requests is that we generate
> excess breadcrumbs and fill the ring much more often with dummy work. We
> have completely undone the outstanding_last_seqno optimisation.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907
> Signed-off-by: Chris Wilson
> Cc: Daniel Vetter
> Cc: Tvrtko Ursulin
> Cc: sta...@vger.kernel.org
Cc: John Harrison
I'd like John's ack on this on too, but patch itself looks sound. Fast r-b
since we've discussed this a while ago already ...
Reviewed-by: Daniel Vetter
> ---
> drivers/gpu/drm/i915/i915_drv.h| 2 --
> drivers/gpu/drm/i915/i915_gem.c| 50
> --
> drivers/gpu/drm/i915/i915_gem_execbuffer.c | 15 +++--
> drivers/gpu/drm/i915/intel_display.c | 2 +-
> drivers/gpu/drm/i915/intel_lrc.c | 4 +--
> drivers/gpu/drm/i915/intel_overlay.c | 8 ++---
> 6 files changed, 30 insertions(+), 51 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 061ecc43d935..de84dd7be971 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2331,7 +2331,6 @@ struct drm_i915_gem_request {
> struct drm_i915_gem_request * __must_check
> i915_gem_request_alloc(struct intel_engine_cs *engine,
> struct intel_context *ctx);
> -void i915_gem_request_cancel(struct drm_i915_gem_request *req);
> void i915_gem_request_free(struct kref *req_ref);
> int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
> struct drm_file *file);
> @@ -2883,7 +2882,6 @@ int i915_gem_sw_finish_ioctl(struct drm_device *dev,
> void *data,
>struct drm_file *file_priv);
> void i915_gem_execbuffer_move_to_active(struct list_head *vmas,
> struct drm_i915_gem_request *req);
> -void i915_gem_execbuffer_retire_commands(struct i915_execbuffer_params
> *params);
> int i915_gem_ringbuffer_submission(struct i915_execbuffer_params *params,
> struct drm_i915_gem_execbuffer2 *args,
> struct list_head *vmas);
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index b6879d43dd74..c6f09e7839ea 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2785,7 +2785,8 @@ __i915_gem_request_alloc(struct intel_engine_cs *engine,
>* fully prepared. Thus it can be cleaned up using the proper
>* free code.
>*/
> - i915_gem_request_cancel(req);
> + intel_ring_reserved_space_cancel(req->ringbuf);
> + i915_gem_request_unreference(req);
> return ret;
> }
>
> @@ -2822,13 +2823,6 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
> return err ? ERR_PTR(err) : req;
> }
>
> -void i915_gem_request_cancel(struct drm_i915_gem_request *req)
> -{
> - intel_ring_reserved_space_cancel(req->ringbuf);
> -
> - i915_gem_request_unreference(req);
> -}
> -
> struct drm_i915_gem_request *
> i915_gem_find_active_request(struct intel_engine_cs *engine)
> {
> @@ -3438,12 +3432,9 @@ int i915_gpu_idle(struct drm_device *dev)
> return PTR_ERR(req);
>
> ret = i915_switch_context(req);
> - if (ret) {
> - i915_gem_request_cancel(req);
> - return ret;
> - }
> -
> i915_add_request_no_flush(req);
> + if (re
[Intel-gfx] [CI-ping 15/15] drm/i915: Late request cancellations are harmful
Conceptually, each request is a record of a hardware transaction - we
build up a list of pending commands and then either commit them to
hardware, or cancel them. However, whilst building up the list of
pending commands, we may modify state outside of the request and make
references to the pending request. If we do so and then cancel that
request, external objects then point to the deleted request leading to
both graphical and memory corruption.
The easiest example is to consider object/VMA tracking. When we mark an
object as active in a request, we store a pointer to this, the most
recent request, in the object. Then we want to free that object, we wait
for the most recent request to be idle before proceeding (otherwise the
hardware will write to pages now owned by the system, or we will attempt
to read from those pages before the hardware is finished writing). If
the request was cancelled instead, that wait completes immediately. As a
result, all requests must be committed and not cancelled if the external
state is unknown.
All that remains of i915_gem_request_cancel() users are just a couple of
extremely unlikely allocation failures, so remove the API entirely.
A consequence of committing all incomplete requests is that we generate
excess breadcrumbs and fill the ring much more often with dummy work. We
have completely undone the outstanding_last_seqno optimisation.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907
Signed-off-by: Chris Wilson
Cc: Daniel Vetter
Cc: Tvrtko Ursulin
Cc: sta...@vger.kernel.org
---
drivers/gpu/drm/i915/i915_drv.h| 2 --
drivers/gpu/drm/i915/i915_gem.c| 50 --
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 15 +++--
drivers/gpu/drm/i915/intel_display.c | 2 +-
drivers/gpu/drm/i915/intel_lrc.c | 4 +--
drivers/gpu/drm/i915/intel_overlay.c | 8 ++---
6 files changed, 30 insertions(+), 51 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 061ecc43d935..de84dd7be971 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2331,7 +2331,6 @@ struct drm_i915_gem_request {
struct drm_i915_gem_request * __must_check
i915_gem_request_alloc(struct intel_engine_cs *engine,
struct intel_context *ctx);
-void i915_gem_request_cancel(struct drm_i915_gem_request *req);
void i915_gem_request_free(struct kref *req_ref);
int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
struct drm_file *file);
@@ -2883,7 +2882,6 @@ int i915_gem_sw_finish_ioctl(struct drm_device *dev, void
*data,
struct drm_file *file_priv);
void i915_gem_execbuffer_move_to_active(struct list_head *vmas,
struct drm_i915_gem_request *req);
-void i915_gem_execbuffer_retire_commands(struct i915_execbuffer_params
*params);
int i915_gem_ringbuffer_submission(struct i915_execbuffer_params *params,
struct drm_i915_gem_execbuffer2 *args,
struct list_head *vmas);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b6879d43dd74..c6f09e7839ea 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2785,7 +2785,8 @@ __i915_gem_request_alloc(struct intel_engine_cs *engine,
* fully prepared. Thus it can be cleaned up using the proper
* free code.
*/
- i915_gem_request_cancel(req);
+ intel_ring_reserved_space_cancel(req->ringbuf);
+ i915_gem_request_unreference(req);
return ret;
}
@@ -2822,13 +2823,6 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
return err ? ERR_PTR(err) : req;
}
-void i915_gem_request_cancel(struct drm_i915_gem_request *req)
-{
- intel_ring_reserved_space_cancel(req->ringbuf);
-
- i915_gem_request_unreference(req);
-}
-
struct drm_i915_gem_request *
i915_gem_find_active_request(struct intel_engine_cs *engine)
{
@@ -3438,12 +3432,9 @@ int i915_gpu_idle(struct drm_device *dev)
return PTR_ERR(req);
ret = i915_switch_context(req);
- if (ret) {
- i915_gem_request_cancel(req);
- return ret;
- }
-
i915_add_request_no_flush(req);
+ if (ret)
+ return ret;
}
ret = intel_engine_idle(engine);
@@ -4943,34 +4934,33 @@ i915_gem_init_hw(struct drm_device *dev)
req = i915_gem_request_alloc(engine, NULL);
if (IS_ERR(req)) {
ret = PTR_ERR(req);
- i915_gem_cleanup_engines(dev);
-
