coccicheck: span checks across CPUs

This adds parallelism by default to the "coccicheck" target using
spatch's "-max" and "-index" arguments.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Nicolas Palix <nicolas.palix@imag.fr>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Documentation/coccinelle.txt

@@ -91,6 +91,11 @@ To enable verbose messages set the V= variable, for example:
 
    make coccicheck MODE=report V=1
 
+By default, coccicheck tries to run as parallel as possible. To change
+the parallelism, set the J= variable. For example, to run across 4 CPUs:
+
+   make coccicheck MODE=report J=4
+
 
  Using Coccinelle with a single semantic patch
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

scripts/coccicheck

@@ -2,15 +2,24 @@
 
 SPATCH="`which ${SPATCH:=spatch}`"
 
+trap kill_running SIGTERM SIGINT
+declare -a SPATCH_PID
+
 # The verbosity may be set by the environmental parameter V=
 # as for example with 'make V=1 coccicheck'
 
 if [ -n "$V" -a "$V" != "0" ]; then
-	VERBOSE=1
+	VERBOSE="$V"
 else
 	VERBOSE=0
 fi
 
+if [ -z "$J" ]; then
+	NPROC=$(getconf _NPROCESSORS_ONLN)
+else
+	NPROC="$J"
+fi
+
 FLAGS="$SPFLAGS -very_quiet"
 
 # spatch only allows include directories with the syntax "-I include"
@@ -69,12 +78,28 @@ if [ "$ONLINE" = "0" ] ; then
 fi
 
 run_cmd() {
+	local i
 	if [ $VERBOSE -ne 0 ] ; then
-		echo "Running: $@"
+		echo "Running ($NPROC in parallel): $@"
 	fi
-	eval $@
+	for i in $(seq 0 $(( NPROC - 1)) ); do
+		eval "$@ -max $NPROC -index $i &"
+		SPATCH_PID[$i]=$!
+		if [ $VERBOSE -eq 2 ] ; then
+			echo "${SPATCH_PID[$i]} running"
+		fi
+	done
+	wait
 }
 
+kill_running() {
+	for i in $(seq $(( NPROC - 1 )) ); do
+		if [ $VERBOSE -eq 2 ] ; then
+			echo "Killing ${SPATCH_PID[$i]}"
+		fi
+		kill ${SPATCH_PID[$i]} 2>/dev/null
+	done
+}
 
 coccinelle () {
     COCCI="$1"