Am 13.12.18 um 13:21 schrieb Chris Wilson:
> Quoting Koenig, Christian (2018-12-13 12:11:10)
>> Am 13.12.18 um 12:37 schrieb Chris Wilson:
>>> Quoting Chunming Zhou (2018-12-11 10:34:45)
>>>> From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
>>>>
>>>> Implement finding the right timeline point in drm_syncobj_find_fence.
>>>>
>>>> v2: return -EINVAL when the point is not submitted yet.
>>>> v3: fix reference counting bug, add flags handling as well
>>>>
>>>> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
>>>> ---
>>>> drivers/gpu/drm/drm_syncobj.c | 43 ++++++++++++++++++++++++++++++++---
>>>> 1 file changed, 40 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
>>>> index 76ce13dafc4d..d964b348ecba 100644
>>>> --- a/drivers/gpu/drm/drm_syncobj.c
>>>> +++ b/drivers/gpu/drm/drm_syncobj.c
>>>> @@ -231,16 +231,53 @@ int drm_syncobj_find_fence(struct drm_file *file_private,
>>>> struct dma_fence **fence)
>>>> {
>>>> struct drm_syncobj *syncobj = drm_syncobj_find(file_private, handle);
>>>> - int ret = 0;
>>>> + struct syncobj_wait_entry wait;
>>>> + int ret;
>>>>
>>>> if (!syncobj)
>>>> return -ENOENT;
>>>>
>>>> *fence = drm_syncobj_fence_get(syncobj);
>>>> - if (!*fence) {
>>>> + drm_syncobj_put(syncobj);
>>>> +
>>>> + if (*fence) {
>>>> + ret = dma_fence_chain_find_seqno(fence, point);
>>>> + if (!ret)
>>>> + return 0;
>>>> + dma_fence_put(*fence);
>>>> + } else {
>>>> ret = -EINVAL;
>>>> }
>>>> - drm_syncobj_put(syncobj);
>>>> +
>>>> + if (!(flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT))
>>>> + return ret;
>>>> +
>>>> + memset(&wait, 0, sizeof(wait));
>>>> + wait.task = current;
>>>> + wait.point = point;
>>>> + drm_syncobj_fence_add_wait(syncobj, &wait);
>>>> +
>>>> + do {
>>>> + set_current_state(TASK_INTERRUPTIBLE);
>>>> + if (wait.fence) {
>>>> + ret = 0;
>>>> + break;
>>>> + }
>>>> +
>>>> + if (signal_pending(current)) {
>>>> + ret = -ERESTARTSYS;
>>>> + break;
>>>> + }
>>>> +
>>>> + schedule();
>>>> + } while (1);
>>> I've previously used a dma_fence_proxy so that we could do nonblocking
>>> waits on future submits. That would be preferrable (a requirement for
>>> our stupid BKL-driven code).
>> That is exactly what I would definitely NAK.
>>
>> I would rather say we should come up with a wait_multiple_events() macro
>> and completely nuke the custom implementation of this in:
>> 1. dma_fence_default_wait and dma_fence_wait_any_timeout
>> 2. the radeon fence implementation
>> 3. the nouveau fence implementation
>> 4. the syncobj code
>>
>> Cause all of them do exactly the same. The dma_fence implementation
>> unfortunately came up with a custom event handling mechanism instead of
>> extending the core Linux wait_event() system.
> I don't want a blocking wait at all.
Ok I wasn't clear enough :) That is exactly what I would NAK!
The wait must be blocking or otherwise you would allow wait-before-signal.
Christian.
> -Chris
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