Commit 8dac00bb authored by Marc-André Lureau's avatar Marc-André Lureau Committed by Markus Armbruster
Browse files

monitor: prevent inserting new monitors after cleanup 



monitor_cleanup() is one of the last things main() calls before it
returns.  In the following patch, monitor_cleanup() will release the
monitor_lock during flushing. There may be pending commands to insert
new monitors, which would modify the mon_list during iteration, and
the clean-up could thus miss those new insertions.

Add a monitor_destroyed global to check if monitor_cleanup() has been
already called. In this case, don't insert the new monitor in the
list, but free it instead. A cleaner solution would involve the main
thread telling other threads to terminate, waiting for their
termination.

Signed-off-by: default avatarMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: default avatarMarkus Armbruster <armbru@redhat.com>
Message-Id: <20181205203737.9011-7-marcandre.lureau@redhat.com>
Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
parent 269d25cd

monitor.c

+17 −2
Original line number Diff line number Diff line
@@ -263,10 +263,11 @@ typedef struct QMPRequest QMPRequest; 
/* QMP checker flags */

#define QMP_ACCEPT_UNKNOWNS 1



/* Protects mon_list, monitor_qapi_event_state.  */

/* Protects mon_list, monitor_qapi_event_state, monitor_destroyed.  */

static QemuMutex monitor_lock;

static GHashTable *monitor_qapi_event_state;

static QTAILQ_HEAD(mon_list, Monitor) mon_list;

static bool monitor_destroyed;



/* Protects mon_fdsets */

static QemuMutex mon_fdsets_lock;
@@ -4538,8 +4539,21 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap) 
static void monitor_list_append(Monitor *mon)

{

    qemu_mutex_lock(&monitor_lock);

    /*

     * This prevents inserting new monitors during monitor_cleanup().

     * A cleaner solution would involve the main thread telling other

     * threads to terminate, waiting for their termination.

     */

    if (!monitor_destroyed) {

        QTAILQ_INSERT_HEAD(&mon_list, mon, entry);

        mon = NULL;

    }

    qemu_mutex_unlock(&monitor_lock);



    if (mon) {

        monitor_data_destroy(mon);

        g_free(mon);

    }

}



static void monitor_qmp_setup_handlers_bh(void *opaque)
@@ -4634,6 +4648,7 @@ void monitor_cleanup(void) 


    /* Flush output buffers and destroy monitors */

    qemu_mutex_lock(&monitor_lock);

    monitor_destroyed = true;

    QTAILQ_FOREACH_SAFE(mon, &mon_list, entry, next) {

        QTAILQ_REMOVE(&mon_list, mon, entry);

        monitor_flush(mon);