Bas Nieuwenhuizen
fa97061a82
To facilitate cross-process timeline semaphores we have to deal with the fact that the syncobj signal operation might be submitted a small finite time after the wait operation. For that we start using DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT during the wait operation so we properly wait instead of returning an error. Furthermore, to make this effective for syncobjs that get reused we actually have to reset them after the wait. Otherwise the wait before submit would get the previous fence instead of waiting for the new thing to submit. The obvious choice, resetting the syncobj after the CS submission has 2 issues though: 1) If the same semaphore is used for wait and signal we can't reset it. This is solvable by only resetting the semaphores that are not in the signal list. 2) The submitted work might be complete before we get to resetting the syncobj. If there is a cycle of submissions that signals it again and finishes before we get to the reset we are screwed. Solution: Copy the fence into a new syncobj and reset the old syncobj before submission. Yes I know it is more syscalls :( At least I reduced the alloc/free overhead by keeping a cache of temporary syncobjs. This also introduces a syncobj_reset_count as we don't want to reset syncobjs that are part of an emulated timeline semaphore. (yes, if the kernel supports timeline syncobjs we should use those instead, but those still need to be implemented and if we depend on them in this patch ordering dependencies get hard ...) Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5600>
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