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events: don't reschedule deleted timeouts/watches

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The deletion of libvirt timeouts/watches is done in 2 steps:
- the first step is synchronous and unregisters the timeout/watch
  from glib mainloop
- the second step is asynchronous and triggered from the first step.
  It releases the memory used for bookkeeping for the timeout/watch
  being deleted

This is done this way to avoid some possible deadlocks when
reentering the sync callback while freeing the memory associated
with the timeout/watch.

However, it's possible to call gvir_event_update_handle after
gvir_event_remove_handle but before _event_handle_remove does
the final cleanup. When this happen, _update_handle will reregister
the handle with glib mainloop, and bad things will happen when
a glib callback is triggered for this event after _event_handle_remove
has freed the memory associated with this handle watch.

This commit marks the timeouts and watches as removed in the
synchronous _remove callback and makes sure removed timeouts/watches
are ignored in _update callbacks.

Based on commit 3e73e0cee977fb20dd29db3ccfe85b00cc386c43 from
libvirt-glib.
Original author: Christophe Fergeau <cfergeau@redhat.com>

Related to: rhbz#1243228
This commit is contained in:
Fabiano Fidêncio 2015-07-22 03:50:08 +02:00
parent 3874a3015d
commit d2c136b020
1 changed files with 14 additions and 3 deletions
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17
src/virt-viewer-events.c
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@ -42,7 +42,7 @@ struct virt_viewer_events_handle
int watch;
int fd;
int events;
int enabled;
int removed;
GIOChannel *channel;
guint source;
virEventHandleCallback cb;
@ -140,7 +140,7 @@ virt_viewer_events_find_handle(int watch)
continue;
}
if (h->watch == watch) {
if ((h->watch == watch) && !h->removed) {
return h;
}
}
@ -240,6 +240,11 @@ virt_viewer_events_remove_handle(int watch)
data->source = 0;
data->events = 0;
/* since the actual watch deletion is done asynchronously, a update_handle call may
* reschedule the watch before it's fully deleted, that's why we need to mark it as
* 'removed' to prevent reuse
*/
data->removed = TRUE;
g_idle_add(virt_viewer_events_cleanup_handle, data);
ret = 0;
@ -252,6 +257,7 @@ struct virt_viewer_events_timeout
{
int timer;
int interval;
int removed;
guint source;
virEventTimeoutCallback cb;
void *opaque;
@ -322,7 +328,7 @@ virt_viewer_events_find_timeout(int timer)
continue;
}
if (t->timer == timer) {
if ((t->timer == timer) && !t->removed) {
return t;
}
}
@ -411,6 +417,11 @@ virt_viewer_events_remove_timeout(int timer)
g_source_remove(data->source);
data->source = 0;
/* since the actual timeout deletion is done asynchronously, a update_timeout call may
* reschedule the timeout before it's fully deleted, that's why we need to mark it as
* 'removed' to prevent reuse
*/
data->removed = TRUE;
g_idle_add(virt_viewer_events_cleanup_timeout, data);
ret = 0;