[Qemu-devel] [PATCH] io/channel-command: Delay the killing of the child after closing the pipe

[Thomas Huth <thuth@redhat.com>]

We are currently facing some migration failure on s390x when running
certain avocado tests, e.g. when running the test
type_specific.io-github-autotest-qemu.migrate.with_reboot.exec.gzip_exec.
This test is using 'migrate -d "exec:nc localhost 5200"' for the migration.
The problem is detected at the receiving side, where the migration stream
apparently ends too early. However, the cause for the problem is the
sending side: After writing the migration stream into the pipe to netcat,
the source QEMU calls qio_channel_command_close() which closes the pipe
and immediately (!) kills the child process afterwards. So if the
sending netcat did not read the final bytes from the pipe yet, or
if it did not manage to send out all its buffers yet, it is killed
before the whole migration stream is passed to the destination side.

To ease the situation at least a little bit, we should give the child
process at least some few more time slices before we kill it with
SIGTERM and then with SIGKILL. With this change, the avocado test now
succeeds here in 10 out of 10 runs.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 io/channel-command.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/io/channel-command.c b/io/channel-command.c
index 319c5ed..f64db3e 100644
--- a/io/channel-command.c
+++ b/io/channel-command.c
@@ -177,11 +177,11 @@ static int qio_channel_command_abort(QIOChannelCommand *ioc,
             return -1;
         }
     } else if (ret == 0) {
-        if (step == 0) {
+        if (step == 4) {
             kill(ioc->pid, SIGTERM);
-        } else if (step == 1) {
+        } else if (step == 8) {
             kill(ioc->pid, SIGKILL);
-        } else {
+        } else if (step >= 9) {
             error_setg(errp,
                        "Process %llu refused to die",
                        (unsigned long long)ioc->pid);
-- 
1.8.3.1