Better pruning of docker images for gen_rtl.sh (#1051)

* better docker pruning in gen_rtl

.buildkite/pipelines/pmg.yml

@@ -30,6 +30,16 @@ env:
 
 steps:
 
+- label: 'setup'
+  commands:
+  - echo "git pull latest to prevent later collisions"
+  - echo "(each init step will try to do its own git pull latest...)"
+  - echo "(assumes all steps use the same host)"
+  - docker pull stanfordaha/garnet:latest
+- wait
+
+
+
 #####################################################################################
 # Two quick RTL checks. Set soft fail so RTL failure does not fail integration tests.
 

mflowgen/common/rtl/gen_rtl.sh

@@ -96,14 +96,6 @@ if [ "$use_container" == True ]; then
       mkdir -p aha; cd aha
       ########################################################################
 
-      # Prune docker images...
-      echo '--- gen_rtl docker prune BEGIN' `date +%H:%M`
-      docker image prune -f -a --filter "until=6h" --filter=label='description=garnet' || true
-
-      echo ""; echo "After pruning:"; echo ""
-      docker images; echo ""
-      docker ps    ; echo ""
-
       # Choose a docker image; can set via "rtl_docker_image" parameter
       default_image="stanfordaha/garnet:latest"
 
@@ -145,6 +137,16 @@ if [ "$use_container" == True ]; then
       # MAKE SURE the docker container gets killed when this script dies.
       trap "docker kill $container_name" EXIT
 
+      # Delete all dangling images created more than 6 hours ago.
+      # Notice that we prune images *after* starting container (pruner
+      # will refuse to kill image w/ active container)
+
+      echo '--- gen_rtl docker prune BEGIN' `date +%H:%M`
+      printf "\nBefore pruning:\n\n";  docker images; echo "";  docker ps; echo ""
+      docker image prune -f -a --filter "until=6h" --filter=label='description=garnet' || true
+      printf "\nAfter pruning:\n\n";   docker images; echo "";  docker ps; echo ""
+      echo '--- Continuing...'
+
       if [ "$use_local_garnet" == True ]; then
         docker exec $container_name /bin/bash -c "rm -rf /aha/garnet"
         # Clone local garnet repo to prevent copying untracked files