On Mon, Jun 18, 2018 at 04:08:53PM +0200, Markus Armbruster wrote:
> From: Peter Xu <pet...@redhat.com>
>
> Before this patch, monitor fd helpers might be called even earlier than
> monitor_init_globals(). This can be problematic.
>
> After previous work, now monitor_init_globals() does not depend on
> accelerator initialization any more. Call it earlier (before CLI
> parsing; that's where the monitor APIs might be called) to make sure it
> is called before any of the monitor APIs.
It looks like this patch moves the creation of the 'IO mon_iothread' to
before the call to os_daemonize().
With qemu 3.0 I'm experiencing crashes when shutting down daemonized
qemu instances, at pthread_join() on the 'IO mon_iothread' thread.
monitor_init_globals() calls monitor_iothread_init(), which in turn uses
iothread_create() to create a joinable thread. Then os_daemonize() is
called after which the thread is no longer "ours".
Debug-writing the thread IDs at pthread_create() and pthread_join()
together with the 'detachable' flag revealed that the mon_iothread ID is
already being reused, in my trace for a detached thread, and the join
then ends with a coredump and ugly log output.
> Suggested-by: Markus Armbruster <arm...@redhat.com>
> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
> Reviewed-by: Markus Armbruster <arm...@redhat.com>
> Signed-off-by: Peter Xu <pet...@redhat.com>
> Message-Id: <20180608035511.7439-7-pet...@redhat.com>
> Signed-off-by: Markus Armbruster <arm...@redhat.com>
> ---
> vl.c | 7 +------
> 1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 6e34fb348d..b3426e03d0 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2978,6 +2978,7 @@ int main(int argc, char **argv, char **envp)
>
> runstate_init();
> postcopy_infrastructure_init();
> + monitor_init_globals();
>
> if (qcrypto_init(&err) < 0) {
> error_reportf_err(err, "cannot initialize crypto: ");
> @@ -4412,12 +4413,6 @@ int main(int argc, char **argv, char **envp)
> default_drive(default_floppy, snapshot, IF_FLOPPY, 0, FD_OPTS);
> default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);
>
> - /*
> - * Note: qtest_enabled() (which is used in monitor_qapi_event_init())
> - * depends on configure_accelerator() above.
> - */
> - monitor_init_globals();
> -
> if (qemu_opts_foreach(qemu_find_opts("mon"),
> mon_init_func, NULL, NULL)) {
> exit(1);
> --
> 2.17.1
