torture: Capture qemu output

Currently qemu output appears on standard output, but is inaccessible
later on.  This commit therefore captures this output and causes
kvm-recheck.sh to output this output if QEMU gave a non-zero non-137
exit code.  (And exit code of 137 indicates that QEMU was killed, in
which case we want to know about the hang rather than the fact that
QEMU was killed.)
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

tools/testing/selftests/rcutorture/bin/kvm-recheck.sh

@@ -30,8 +30,16 @@ do
 		TORTURE_SUITE="`cat $i/../TORTURE_SUITE`"
 		rm -f $i/console.log.*.diags
 		kvm-recheck-${TORTURE_SUITE}.sh $i
-		if test -f "$i/console.log"
+		if test -f "$i/qemu-retval" && test "`cat $i/qemu-retval`" -ne 0 && test "`cat $i/qemu-retval`" -ne 137
 		then
+			echo QEMU error, output:
+			cat $i/qemu-output
+		elif test -f "$i/console.log"
+		then
+			if test -f "$i/qemu-retval" && test "`cat $i/qemu-retval`" -eq 137
+			then
+				echo QEMU killed
+			fi
 			configcheck.sh $i/.config $i/ConfigFragment
 			if test -r $i/Make.oldconfig.err
 			then

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

@@ -165,7 +165,7 @@ then
 fi
 echo "NOTE: $QEMU either did not run or was interactive" > $resdir/console.log
 echo $QEMU $qemu_args -m $TORTURE_QEMU_MEM -kernel $KERNEL -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
-( $QEMU $qemu_args -m $TORTURE_QEMU_MEM -kernel $KERNEL -append "$qemu_append $boot_args"& echo $! > $resdir/qemu_pid; wait `cat  $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
+( $QEMU $qemu_args -m $TORTURE_QEMU_MEM -kernel $KERNEL -append "$qemu_append $boot_args" > $resdir/qemu-output 2>&1 & 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"