rcutorture: Don't rebuild identical kernel

Currently, if the user specifies multiple runs of a given test
configuration, the scripting does multiple kernel builds.  This wastes
both time and disk space, so this commit makes the scripting use the
first build for all runs of a given test configuration.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh

@@ -91,25 +91,33 @@ fi
 # CONFIG_PCMCIA=n
 # CONFIG_CARDBUS=n
 # CONFIG_YENTA=n
-if kvm-build.sh $config_template $builddir $T
+base_resdir=`echo $resdir | sed -e 's/\.[0-9]\+$//'`
+if test "$base_resdir" != "$resdir" -a -f $base_resdir/bzImage -a -f $base_resdir/vmlinux
 then
+	# Rerunning previous test, so use that test's kernel.
+	QEMU="`identify_qemu $base_resdir/vmlinux`"
+	KERNEL=$base_resdir/bzImage
+	ln -s $base_resdir/Make*.out $resdir  # for kvm-recheck.sh
+	ln -s $base_resdir/.config $resdir  # for kvm-recheck.sh
+elif kvm-build.sh $config_template $builddir $T
+then
+	# Had to build a kernel for this test.
 	QEMU="`identify_qemu $builddir/vmlinux`"
 	BOOT_IMAGE="`identify_boot_image $QEMU`"
 	cp $builddir/Make*.out $resdir
+	cp $builddir/vmlinux $resdir
 	cp $builddir/.config $resdir
 	if test -n "$BOOT_IMAGE"
 	then
 		cp $builddir/$BOOT_IMAGE $resdir
+		KERNEL=$resdir/bzImage
 	else
 		echo No identifiable boot image, not running KVM, see $resdir.
 		echo Do the torture scripts know about your architecture?
 	fi
 	parse-build.sh $resdir/Make.out $title
-	if test -f $builddir.wait
-	then
-		mv $builddir.wait $builddir.ready
-	fi
 else
+	# Build failed.
 	cp $builddir/Make*.out $resdir
 	cp $builddir/.config $resdir || :
 	echo Build failed, not running KVM, see $resdir.
@@ -119,6 +127,10 @@ else
 	fi
 	exit 1
 fi
+if test -f $builddir.wait
+then
+	mv $builddir.wait $builddir.ready
+fi
 while test -f $builddir.ready
 do
 	sleep 1
@@ -166,8 +178,8 @@ then
 	exit 0
 fi
 echo "NOTE: $QEMU either did not run or was interactive" > $resdir/console.log
-echo $QEMU $qemu_args -m 512 -kernel $resdir/bzImage -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
-( $QEMU $qemu_args -m 512 -kernel $resdir/bzImage -append "$qemu_append $boot_args"& echo $! > $resdir/qemu_pid; wait `cat  $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
+echo $QEMU $qemu_args -m 512 -kernel $KERNEL -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
+( $QEMU $qemu_args -m 512 -kernel $KERNEL -append "$qemu_append $boot_args"& echo $! > $resdir/qemu_pid; wait `cat  $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
 commandcompleted=0
 sleep 10 # Give qemu's pid a chance to reach the file
 if test -s "$resdir/qemu_pid"