[kvm-unit-tests PATCH v7 02/35] arch-run: Keep infifo open

[Nicholas Piggin <npiggin@gmail.com>]

The infifo fifo that is used to send characters to QEMU console is
only able to receive one character before the cat process exits.
Supporting interactions between test and harness involving multiple
characters requires the fifo to remain open.

The infifo is removed by the exit handler like other files and fifos
so it does not have to be removed explicitly.

With this we can let the cat out of the subshell, simplifying the
input pipeline.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 scripts/arch-run.bash | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/scripts/arch-run.bash b/scripts/arch-run.bash
index e34d784c0..39419d4e2 100644
--- a/scripts/arch-run.bash
+++ b/scripts/arch-run.bash
@@ -158,6 +158,11 @@ run_migration ()
 	mkfifo ${src_outfifo}
 	mkfifo ${dst_outfifo}
 
+	# Holding both ends of the input fifo open prevents opens from
+	# blocking and readers getting EOF when a writer closes it.
+	mkfifo ${dst_infifo}
+	exec {dst_infifo_fd}<>${dst_infifo}
+
 	eval "$migcmdline" \
 		-chardev socket,id=mon,path=${src_qmp},server=on,wait=off \
 		-mon chardev=mon,mode=control > ${src_outfifo} &
@@ -191,14 +196,10 @@ run_migration ()
 
 do_migration ()
 {
-	# We have to use cat to open the named FIFO, because named FIFO's,
-	# unlike pipes, will block on open() until the other end is also
-	# opened, and that totally breaks QEMU...
-	mkfifo ${dst_infifo}
 	eval "$migcmdline" \
 		-chardev socket,id=mon,path=${dst_qmp},server=on,wait=off \
 		-mon chardev=mon,mode=control -incoming unix:${dst_incoming} \
-		< <(cat ${dst_infifo}) > ${dst_outfifo} &
+		< ${dst_infifo} > ${dst_outfifo} &
 	incoming_pid=$!
 	cat ${dst_outfifo} | tee ${dst_out} | filter_quiet_msgs &
 
@@ -245,7 +246,6 @@ do_migration ()
 
 	# keypress to dst so getchar completes and test continues
 	echo > ${dst_infifo}
-	rm ${dst_infifo}
 
 	# Wait for the incoming socket being removed, ready for next destination
 	while [ -S ${dst_incoming} ] ; do sleep 0.1 ; done
-- 
2.42.0