Commit 85117701 authored by Wolfgang Bumiller's avatar Wolfgang Bumiller Committed by Markus Armbruster
Browse files

monitor: delay monitor iothread creation 



Commit d32749de moved the call to monitor_init_globals()
to before os_daemonize(), making it an unsuitable place to
spawn the monitor iothread as it won't be inherited over the
fork() in os_daemonize().

We now spawn the thread the first time we instantiate a
monitor which actually has use_io_thread == true.
Instantiation of monitors happens only after os_daemonize().
We still need to create the qmp_dispatcher_bh when not using
iothreads, so this now still happens in
monitor_init_globals().

Signed-off-by: default avatarWolfgang Bumiller <w.bumiller@proxmox.com>
Fixes: d32749de ("monitor: move init global earlier")
Message-Id: <20180925081507.11873-3-w.bumiller@proxmox.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Tested-by: default avatarPeter Xu <peterx@redhat.com>
[This fixes a crash on shutdown with --daemonize]
Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
parent 9a3e52e3

monitor.c

+21 −14
Original line number Diff line number Diff line
@@ -708,9 +708,14 @@ static void monitor_qapi_event_init(void) 


static void handle_hmp_command(Monitor *mon, const char *cmdline);



static void monitor_iothread_init(void);



static void monitor_data_init(Monitor *mon, bool skip_flush,

                              bool use_io_thread)

{

    if (use_io_thread && !mon_iothread) {

        monitor_iothread_init();

    }

    memset(mon, 0, sizeof(Monitor));

    qemu_mutex_init(&mon->mon_lock);

    qemu_mutex_init(&mon->qmp.qmp_queue_lock);
@@ -4461,15 +4466,6 @@ static AioContext *monitor_get_aio_context(void) 
static void monitor_iothread_init(void)

{

    mon_iothread = iothread_create("mon_iothread", &error_abort);



    /*

     * The dispatcher BH must run in the main loop thread, since we

     * have commands assuming that context.  It would be nice to get

     * rid of those assumptions.

     */

    qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),

                                   monitor_qmp_bh_dispatcher,

                                   NULL);

}



void monitor_init_globals(void)
@@ -4479,7 +4475,15 @@ void monitor_init_globals(void) 
    sortcmdlist();

    qemu_mutex_init(&monitor_lock);

    qemu_mutex_init(&mon_fdsets_lock);

    monitor_iothread_init();



    /*

     * The dispatcher BH must run in the main loop thread, since we

     * have commands assuming that context.  It would be nice to get

     * rid of those assumptions.

     */

    qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),

                                   monitor_qmp_bh_dispatcher,

                                   NULL);

}



/* These functions just adapt the readline interface in a typesafe way.  We
@@ -4624,7 +4628,9 @@ void monitor_cleanup(void) 
     * we need to unregister from chardev below in

     * monitor_data_destroy(), and chardev is not thread-safe yet

     */

    if (mon_iothread) {

        iothread_stop(mon_iothread);

    }



    /* Flush output buffers and destroy monitors */

    qemu_mutex_lock(&monitor_lock);
@@ -4639,10 +4645,11 @@ void monitor_cleanup(void) 
    /* QEMUBHs needs to be deleted before destroying the I/O thread */

    qemu_bh_delete(qmp_dispatcher_bh);

    qmp_dispatcher_bh = NULL;



    if (mon_iothread) {

        iothread_destroy(mon_iothread);

        mon_iothread = NULL;

    }

}



QemuOptsList qemu_mon_opts = {

    .name = "mon",