torture: Make kvm-test-1-run-qemu.sh check for reboot loops

It turns out that certain types of early boot bugs can result in reboot
loops, even within a guest OS running under qemu/KVM.  This commit
therefore upgrades the kvm-test-1-run-qemu.sh script's hang-detection
heuristics to detect such situations and to terminate the run when
they occur.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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

@@ -159,9 +159,13 @@ then
 		then
 			last_ts=0
 		fi
-		if test "$newline" != "$oldline" && test "$last_ts" -lt $((seconds + $TORTURE_SHUTDOWN_GRACE))
+		if test "$newline" != "$oldline" && test "$last_ts" -lt $((seconds + $TORTURE_SHUTDOWN_GRACE)) && test "$last_ts" -gt "$TORTURE_SHUTDOWN_GRACE"
 		then
 			must_continue=yes
+			if test $kruntime -ge $((seconds + $TORTURE_SHUTDOWN_GRACE))
+			then
+				echo Continuing at console.log time $last_ts \"`tail -n 1 $resdir/console.log`\" `date`
+			fi
 		fi
 		if test $must_continue = no && test $kruntime -ge $((seconds + $TORTURE_SHUTDOWN_GRACE))
 		then