On Mon, 4 Jun 2018 13:03:45 +0100
Daniel P. Berrangé <berra...@redhat.com> wrote:
> When using --daemonize, the initial lead process will fork a child and
> then wait to be notified that setup is complete via a pipe, before it
> exits. When using --preconfig there is an extra call to main_loop()
> before the notification is done from os_setup_post(). Thus the parent
> process won't exit until the mgmt application connects to the monitor
> and tells QEMU to leave the RUN_STATE_PRECONFIG. The mgmt application
> won't connect to the monitor until daemonizing has completed though.
>
> This is a chicken and egg problem, leading to deadlock at startup.
>
> The only viable way to fix this is to call os_setup_post() before
> the early main_loop() call when in RUN_STATE_PRECONFIG. This has the
> downside that any errors from this point onwards won't be handled
> well by the mgmt application, because it will think QEMU has started
> successfully, so not be expecting an abrupt exit. The only way to
> deal with that is to move as much user input validation as possible
> to before the main_loop() call. This is left as an exercise for
> future interested developers.
>
> Signed-off-by: Daniel P. Berrangé <berra...@redhat.com>
[...]
How about combining ideas from yours and Michal's patches?
It should fix broken iotests/libvirt sync point and
we can think about NONE runstate idea at without rushing it.
If it looks acceptable, I'll post proper patches + test case for it
after some testing (to ensure that iotests Max pointed out are working
as expected)
diff --git a/vl.c b/vl.c
index c4fe255..a2062d6 100644
--- a/vl.c
+++ b/vl.c
@@ -1953,10 +1953,15 @@ static bool main_loop_should_exit(void)
static void main_loop(void)
{
+ static bool os_setup_post_done = false;
#ifdef CONFIG_PROFILER
int64_t ti;
#endif
- do {
+ if (!os_setup_post_done) {
+ os_setup_post();
+ os_setup_post_done = true;
+ }
+ while (!main_loop_should_exit()) {
#ifdef CONFIG_PROFILER
ti = profile_getclock();
#endif
@@ -1964,7 +1969,7 @@ static void main_loop(void)
#ifdef CONFIG_PROFILER
dev_time += profile_getclock() - ti;
#endif
- } while (!main_loop_should_exit());
+ }
}
static void version(void)
