Hello,

While trying to use buildkit through docker build, my dockerd daemon seems to go in a infinite loop and the docker build is hanging.

Version: Docker version 19.03.5, build 633a0ea838
Processes (ps axu | grep docker):

root      5822 96.6  0.9 2460340 290756 ?      Ssl  18:29  45:16 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
tc0      26084  0.2  0.2 1080756 72472 ?       Sl   18:51   0:03 docker build --build-arg ...

While looking into the trace, I found lot of occurence of github.com/docker/docker/vendor/github.com/moby/buildkit/solver.(*cacheManager).filterResults:173
But I'm not a specialist of this kind of trace, so may be I'm not reading it right.

The trace is here: out.gz (remove the .gz if needed).
Trace extracted with curl --unix-socket /var/run/docker.sock http://./debug/pprof/trace

The CPU usage does not go down when I stop the docker build process (still using 100%).

@tonistiigi I already had an issue around cache and LoadWithParents (#1250, fixed by you, thx), while building the same Dockerfile.

Let me know if you have any idea about the issue and what I can do to dig further.