tcwg_kernel-bisect.sh: Simplify linux-next rebase workaround

Linux-next:master rebases almost every day on top of the Linus's tree
(aka linux-next:stable), which creates problems for bisections.

We have tried to workaround these rebases, but results are still not
ideal.  This patch reworks (and simplifies!) handling of linux-next.

The goal of testing linux-next:master is to detect regressions before they
reach Linus's tree (linux-next:stable).  Therefore, we are really only
interested in regressions between linux-next:stable and linux-next:master
(regressions in Linus's tree will be bisected in another job anyway).

So the new workaround is to force baseline_rev to linux-next:stable
and be done with it!

This also allows us to remove confusing distinction between
baseline_rev and good_rev.

Change-Id: I96002f1d21f68e353c0b62837c4968bf956ecbf2

1 files changed, 34 insertions, 59 deletions

diff --git a/tcwg_kernel-bisect.sh b/tcwg_kernel-bisect.sh
index 2bde3c3f..196633a4 100755
--- a/tcwg_kernel-bisect.sh
+++ b/tcwg_kernel-bisect.sh
@@ -39,6 +39,24 @@ if $verbose; then set -x; fi
 
 trap "eval \"echo ERROR at \${FUNCNAME[0]}:\${BASH_LINENO[0]}\" > $artifacts/failures" EXIT
 
+rebase_workaround=false
+
+if [ x"$ci_project" = x"tcwg_kernel" ] \
+       && [ x"$current_project" = x"linux" -a x"${rr[linux_version]}" = x"next" ]; then
+    # Workaround linux-next/master rebasing on top of linux-next/stable.
+    # Search for regressions against linux-mainline:master (aka linux-next:stable).
+    clone_or_update_repo $current_project stable ${rr[linux_url]}
+    # Just in case linux-next:stable has advanced between the build and bisect jobs,
+    # use merge base between linux-next:stable and $bad_rev.
+    linux_next_stable="${linux_next_stable-$(git -C $current_project merge-base HEAD $bad_rev)}"
+    cat <<EOF | manifest_out
+declare -g linux_next_stable=$linux_next_stable
+EOF
+    echo "Rebase workaround: forcing baseline_rev to $linux_next_stable"
+    baseline_rev=$linux_next_stable
+    rebase_workaround=true
+fi
+
 # Build baseline that we are going to re-use to speed-up bisection.
 # (This also confirms that infrastructure is OK.)
 echo "Testing baseline_rev $baseline_rev (should be success)"
@@ -118,68 +136,25 @@ fi
 EOF
 chmod +x $artifacts/test.sh
 
-# Workaround linux-next/master rebasing on top of linux-next/stable.
-# Try to find $good_rev that is "good" compared to baseline
-# and that is an ancesstor of both $baseline_rev and $bad_rev.
-merge_base=$(git merge-base $bad_rev $baseline_rev)
-origin=$(git remote get-url origin)
-origin=$(basename "$origin")
-if [ x"$merge_base" != x"$baseline_rev" -a x"$origin" = x"linux-next.git" ]; then
-    # Try to use merge_base (just like git-bisect).
-    try_revs=($merge_base)
-
-    # Check if we can use linux-next/stable as our 2nd try.
-    linux_next_stable="${linux_next_stable-$(git rev-parse refs/remotes/origin/stable)}"
-    cat <<EOF | manifest_out
-declare -g linux_next_stable=$linux_next_stable
-EOF
-    try_revs+=($linux_next_stable)
-
-    # Check if we can use linux-mainline/master as our last resort.
-    url=git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
-    git remote add mainline "$url" > /dev/null 2>&1 || true
-    git remote set-url mainline "$url"
-    clone_or_update_repo . refs/remotes/mainline/master "$url"
-    mainline_master="${mainline_master-$(git merge-base $bad_rev HEAD)}"
-    cat <<EOF | manifest_out
-declare -g mainline_master=$mainline_master
-EOF
-    try_revs+=($mainline_master)
-
-    for good_rev in "${try_revs[@]}"; do
-	echo "Linux-next rebase workaround: testing potential good_rev $good_rev (hoping for success)"
-	git checkout --detach "$good_rev"
-	$artifacts/test.sh &
-	res=0 && wait $! || res=$?
-	if [ x"$res" = x"0" ]; then
-	    break
-	fi
-    done
-
-    if [ x"$res" != x"0" ]; then
-	# Below bisect will fail :-(
-	echo "Linux-next rebase workaround: could not find a good parent, below bisect will fail"
-	good_rev=$baseline_rev
-    fi
-else
-    good_rev=$baseline_rev
-fi
-
-ln -f -s "build-$good_rev" "$artifacts/build-good"
-ln -f -s "build-$good_rev.sh" "$artifacts/manifests/build-good.sh"
-
 git checkout --detach $bad_rev
 $artifacts/test.sh &
 res=0 && wait $! || res=$?
 
 if [ x"$res" = x"0" ]; then
-    echo "WARNING: build for bad_rev $bad_rev succeeded"
-    # Build job had a spurious failure.  Re-try.
-    cat > $artifacts/trigger-2-build-master <<EOF
+    touch $artifacts/jenkins/build-name
+    if $rebase_workaround; then
+	echo "Rebase workaround: no regression between $baseline_rev and $bad_rev"
+	sed -i -e "s/\$/-bad_rev-good/" $artifacts/jenkins/build-name
+    else
+	echo "WARNING: build for bad_rev $bad_rev succeeded"
+	# Build job had a spurious failure.  Re-try.
+	cat > $artifacts/trigger-2-build-master <<EOF
 current_project=$current_project
 current_branch=$bad_rev
 EOF
-    rm -f $artifacts/jenkins/mail-recipients.txt
+	sed -i -e "s/\$/-spurious/" $artifacts/jenkins/build-name
+    fi
+    echo > $artifacts/jenkins/mail-recipients.txt
     trap "" EXIT
     exit 0
 fi
@@ -187,7 +162,7 @@ fi
 ln -f -s "build-$bad_rev" "$artifacts/build-bad"
 ln -f -s "build-$bad_rev.sh" "$artifacts/manifests/build-bad.sh"
 
-git bisect start $bad_rev $good_rev 2>&1 | tee $artifacts/bisect.log
+git bisect start $bad_rev $baseline_rev 2>&1 | tee $artifacts/bisect.log
 
 # "git bisect run" can fail (exit with non-zero) in a number of cases:
 # - on trivial bisects (e.g., between HEAD^ and HEAD),
@@ -244,10 +219,10 @@ EOF
 else
     first_bad=$(git rev-parse HEAD)
     if ! [ -f .git/BISECT_LOG ]; then
-	# It seems this was a trivial bisect with $bad_rev^ == $good_rev.
+	# It seems this was a trivial bisect with $bad_rev^ == $baseline_rev.
 	first_bad=$bad_rev
 	last_good=$(git rev-parse $first_bad^)
-	assert [ x"$last_good" = x"$good_rev" ]
+	assert [ x"$last_good" = x"$baseline_rev" ]
 
 	echo $first_bad > $artifacts/first-bad
     fi
@@ -284,8 +259,8 @@ $(git -C $current_project log -n 1 $first_bad)
 
 EOF
 else
-    good_name="good_rev"
-    good_sha1="$good_rev"
+    good_name="baseline_rev"
+    good_sha1="$baseline_rev"
     bad_name="bad"
     bad_sha1="$bad_rev"
     cat >> $artifacts/jenkins/mail-body.txt <<EOF