On Wed, May 19, 2021 at 5:06 PM Jason Ekstrand jason@jlekstrand.net wrote:
Once we no longer rely on error propagation, I think there's a lot we can rip out.
I honestly did not find that much ... what did you uncover? -Daniel
--Jason
On Wed, May 19, 2021 at 5:15 AM Daniel Vetter daniel.vetter@ffwll.ch wrote:
From: Jason Ekstrand jason@jlekstrand.net
This reverts commit 9e31c1fe45d555a948ff66f1f0e3fe1f83ca63f7. Ever since that commit, we've been having issues where a hang in one client can propagate to another. In particular, a hang in an app can propagate to the X server which causes the whole desktop to lock up.
Error propagation along fences sound like a good idea, but as your bug shows, surprising consequences, since propagating errors across security boundaries is not a good thing.
What we do have is track the hangs on the ctx, and report information to userspace using RESET_STATS. That's how arb_robustness works. Also, if my understanding is still correct, the EIO from execbuf is when your context is banned (because not recoverable or too many hangs). And in all these cases it's up to userspace to figure out what is all impacted and should be reported to the application, that's not on the kernel to guess and automatically propagate.
What's more, we're also building more features on top of ctx error reporting with RESET_STATS ioctl: Encrypted buffers use the same, and the userspace fence wait also relies on that mechanism. So it is the path going forward for reporting gpu hangs and resets to userspace.
So all together that's why I think we should just bury this idea again as not quite the direction we want to go to, hence why I think the revert is the right option here.Signed-off-by: Jason Ekstrand jason.ekstrand@intel.com
v2: Augment commit message. Also restore Jason's sob that I accidentally lost.
Signed-off-by: Jason Ekstrand jason.ekstrand@intel.com (v1) Reported-by: Marcin Slusarz marcin.slusarz@intel.com Cc: stable@vger.kernel.org # v5.6+ Cc: Jason Ekstrand jason.ekstrand@intel.com Cc: Marcin Slusarz marcin.slusarz@intel.com Cc: Jon Bloomfield jon.bloomfield@intel.com Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3080 Fixes: 9e31c1fe45d5 ("drm/i915: Propagate errors on awaiting already signaled fences") Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch
drivers/gpu/drm/i915/i915_request.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index 970d8f4986bb..b796197c0772 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -1426,10 +1426,8 @@ i915_request_await_execution(struct i915_request *rq,
do { fence = *child++;
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {i915_sw_fence_set_error_once(&rq->submit, fence->error);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) continue;
} if (fence->context == rq->fence.context) continue;@@ -1527,10 +1525,8 @@ i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence)
do { fence = *child++;
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {i915_sw_fence_set_error_once(&rq->submit, fence->error);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) continue;
} /* * Requests on the same timeline are explicitly ordered, along-- 2.31.0