Make witness mode a first-class citizen

This change introduces a top-level make witness target that builds a dot
graph and if graphviz is available, an SVG file as well. A shell script
replaces the previous python script that no longer works. Instead of
fixing witness.py, which is probably trivial, the shell script does an
intermediate pass and programmatically looks for cycles using tsort(1).

Checking lock dependencies becomes actionable in a CI context.

The script also takes explicit test directories on purpose, to have the
ability to aggregate test results from multiple executions. For example
when the test suite is run on various operating systems or with varying
privileges to cover feature-conditional tests.

.gitignore

@@ -144,6 +144,10 @@ cscope.*out
 /cov-int
 /myproject.tgz
 
+# Witness droppings
+witness.dot
+witness.svg
+
 # Flexelint droppings
 _.fl
 _.fl.old

Makefile.am

@@ -8,7 +8,13 @@ pkgconfig_DATA = varnishapi.pc
 m4dir = $(datadir)/aclocal
 m4_DATA = varnish.m4 varnish-legacy.m4
 
-CLEANFILES = cscope.in.out cscope.out cscope.po.out
+CLEANFILES = \
+	cscope.in.out \
+	cscope.out \
+	cscope.po.out \
+	witness.dot \
+	witness.svg
+
 EXTRA_DIST = \
 	README.rst \
 	README.Packaging \
@@ -52,4 +58,24 @@ cscope:
 gcov_digest:
 	${PYTHON} tools/gcov_digest.py -o _gcov
 
-.PHONY: cscope
+witness.dot: all
+	$(MAKE) -C bin/varnishtest check AM_VTC_LOG_FLAGS=-pdebug=+witness
+	$(AM_V_GEN) $(srcdir)/tools/witness.sh witness.dot bin/varnishtest
+
+.dot.svg:
+if ! HAVE_DOT
+	@echo ==================================================
+	@echo You need graphviz installed to generate svg output
+	@echo ==================================================
+	@false
+else
+	$(AM_V_GEN) $(DOT) -Tsvg $< >$@
+endif
+
+if HAVE_DOT
+witness: witness.svg
+else
+witness: witness.dot
+endif
+
+.PHONY: cscope witness.dot

bin/varnishtest/witness.py

-#!/usr/bin/env python3
-#
-# This script is in the public domain
-#
-# Run instructions:
-#       varnishtest -W -iv -j <pick_a_number> > _.w
-#       python witness.py
-#       dot -Tpng /tmp/_.dot > /tmp/_.png
-
-d = dict()
-a = dict()
-
-fi = open("_.w")
-fo = open("/tmp/_.dot", "w")
-
-fo.write('''digraph {
-    #rotate="90"
-    #page="8.2,11.7"
-    size="8.2,11.7"
-    rankdir="LR"
-    node [fontname="Inconsolata", fontsize="10"]
-    edge [fontname="Inconsolata", fontsize="10"]
-''')
-
-for i in fi:
-    l = "ROOT"
-    j = i.split()
-    if len(j) < 8:
-        continue
-    if j[1][0] != 'v':
-        continue
-    if j[3] != "vsl|":
-        continue
-    if j[5] != "Witness":
-        continue
-    t = j[7:]
-    tt = str(t)
-    if tt in d:
-        continue
-    d[tt] = True
-    for e in t:
-        f = e.split(",")
-        x = '"%s" -> "%s" [label="%s(%s)"]\n' % (l, f[0], f[1], f[2])
-        if not x in a:
-            a[x] = True
-            fo.write(x)
-        l = f[0]
-
-fo.write("}\n")
-

tools/witness.sh

+#!/bin/sh
+
+set -e
+set -u
+
+readonly work_dir=$(mktemp -d)
+trap 'rm -rf "$work_dir"' EXIT
+
+witness_full_paths() {
+	find "$@" -name '*.log' -print0 |
+	xargs -0 awk '$3 == "vsl|" && $5 == "Witness" {
+		printf "%s", "ROOT"
+		for (i = 7; i <= NF; i++) {
+			printf " %s", $i
+		}
+		printf "\n"
+	}' |
+	sort |
+	uniq
+}
+
+witness_edges() {
+	awk '{
+		for (i = 1; i < NF; i++) {
+			printf "%s %s\n", $i, $(i + 1)
+		}
+	}' |
+	sort |
+	uniq
+}
+
+witness_cycles() {
+	! awk -F '[ ,]' '{print $1 " " $(NF - 2)}' |
+	tsort >/dev/null 2>&1
+}
+
+witness_graph() {
+	cat <<-EOF
+	digraph {
+	    size="8.2,11.7"
+	    rankdir="LR"
+	    node [fontname="Inconsolata", fontsize="10"]
+	    edge [fontname="Inconsolata", fontsize="10"]
+	EOF
+
+	awk -F '[ ,]' '{
+		printf "    \"%s\" -> \"%s\" [label=\"%s(%s)\"]\n",
+		    $1, $(NF - 2), $(NF - 1), $NF
+	}' |
+	sort |
+	uniq
+
+	echo '}'
+}
+
+if [ $# -lt 2 ]
+then
+	cat >&2 <<-EOF
+	usage: $0 dot_file test_dirs...
+	EOF
+	exit 1
+fi
+
+dest_file=$1
+shift
+
+witness_full_paths "$@" |
+witness_edges >"$work_dir/witness-edges.txt"
+
+tsort_err=
+
+if witness_cycles <"$work_dir/witness-edges.txt"
+then
+	echo "Error: lock cycle witnessed" >&2
+	tsort_err=1
+fi
+
+witness_graph <"$work_dir/witness-edges.txt" >"$work_dir/witness.dot"
+
+mv "$work_dir/witness.dot" "$dest_file"
+
+exit $tsort_err