Op 05-10-2021 om 13:37 schreef Christian König:
> Simplifying the code a bit.
>
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_wait.c | 51 +++++-------------------
> 1 file changed, 9 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_wait.c b/drivers/gpu/drm/i915/gem/i915_gem_wait.c
> index f909aaa09d9c..a13193db1dba 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_wait.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_wait.c
> @@ -37,55 +37,22 @@ i915_gem_object_wait_reservation(struct dma_resv *resv,
> unsigned int flags,
> long timeout)
> {
> - struct dma_fence *excl;
> - bool prune_fences = false;
> -
> - if (flags & I915_WAIT_ALL) {
> - struct dma_fence **shared;
> - unsigned int count, i;
> - int ret;
> + struct dma_resv_iter cursor;
> + struct dma_fence *fence;
>
> - ret = dma_resv_get_fences(resv, &excl, &count, &shared);
> - if (ret)
> - return ret;
> -
> - for (i = 0; i < count; i++) {
> - timeout = i915_gem_object_wait_fence(shared[i],
> - flags, timeout);
> - if (timeout < 0)
> - break;
> -
> - dma_fence_put(shared[i]);
> - }
> -
> - for (; i < count; i++)
> - dma_fence_put(shared[i]);
> - kfree(shared);
> -
> - /*
> - * If both shared fences and an exclusive fence exist,
> - * then by construction the shared fences must be later
> - * than the exclusive fence. If we successfully wait for
> - * all the shared fences, we know that the exclusive fence
> - * must all be signaled. If all the shared fences are
> - * signaled, we can prune the array and recover the
> - * floating references on the fences/requests.
> - */
> - prune_fences = count && timeout >= 0;
> - } else {
> - excl = dma_resv_get_excl_unlocked(resv);
> + dma_resv_iter_begin(&cursor, resv, flags & I915_WAIT_ALL);
> + dma_resv_for_each_fence_unlocked(&cursor, fence) {
> + timeout = i915_gem_object_wait_fence(fence, flags, timeout);
> + if (timeout < 0)
> + break;
> }
> -
> - if (excl && timeout >= 0)
> - timeout = i915_gem_object_wait_fence(excl, flags, timeout);
> -
> - dma_fence_put(excl);
> + dma_resv_iter_end(&cursor);
>
> /*
> * Opportunistically prune the fences iff we know they have *all* been
> * signaled.
> */
> - if (prune_fences)
> + if (timeout > 0)
> dma_resv_prune(resv);
>
> return timeout;
When replying to tvrtko about correctness of the conversion, I just now noticed a logic bug here, the same logic bug also affects dma_resv_wait_timeout.
long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr,
unsigned long timeout)
{
long ret = timeout ? timeout : 1;
struct dma_resv_iter cursor;
struct dma_fence *fence;
dma_resv_iter_begin(&cursor, obj, wait_all);
dma_resv_for_each_fence_unlocked(&cursor, fence) {
ret = dma_fence_wait_timeout(fence, intr, ret);
if (ret <= 0) {
dma_resv_iter_end(&cursor);
return ret;
}
}
dma_resv_iter_end(&cursor);
return ret;
}
It fails to handle the case correctly when timeout = 0, I think the original code probably did.
dma_fence_wait_timeout should be called with timeout = 0 explicitly.
Fixed code for inner loop:
ret = dma_fence_wait_timeout(fence, intr, timeout);
if (ret <= 0) break;
if (timeout) timeout = ret;
This bug also affects i915_gem_object_wait_reservation, so the whole series might need to be
respinned, or at least checked, if more wait conversions are affected.
~Maarten
