[Xen-changelog] [xen-unstable] Mem event: don't leave zombie domains if there are wait-queued vcpus

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Tim Deegan <tim@xxxxxxx>
# Date 1331809964 0
# Node ID 2144deeb3da12aa85169ac4b1a445343418ac799
# Parent  17dd1004c4b99176a1ee190fd33b051fb5df38f8
Mem event: don't leave zombie domains if there are wait-queued vcpus

Vcpus in wait queues retain a domain reference. Upon domain destruction, we
were not taking care of draining the wait queues.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Acked-by: Tim Deegan <tim@xxxxxxx>
Committed-by: Tim Deegan <tim@xxxxxxx>
---


diff -r 17dd1004c4b9 -r 2144deeb3da1 xen/arch/x86/mm/mem_event.c
--- a/xen/arch/x86/mm/mem_event.c       Thu Mar 15 10:09:03 2012 +0000
+++ b/xen/arch/x86/mm/mem_event.c       Thu Mar 15 11:12:44 2012 +0000
@@ -489,12 +489,25 @@
 /* Clean up on domain destruction */
 void mem_event_cleanup(struct domain *d)
 {
-    if ( d->mem_event->paging.ring_page )
+    if ( d->mem_event->paging.ring_page ) {
+        /* Destroying the wait queue head means waking up all
+         * queued vcpus. This will drain the list, allowing
+         * the disable routine to complete. It will also drop
+         * all domain refs the wait-queued vcpus are holding.
+         * Finally, because this code path involves previously
+         * pausing the domain (domain_kill), unpausing the 
+         * vcpus causes no harm. */
+        destroy_waitqueue_head(&d->mem_event->paging.wq);
         (void)mem_event_disable(d, &d->mem_event->paging);
-    if ( d->mem_event->access.ring_page )
+    }
+    if ( d->mem_event->access.ring_page ) {
+        destroy_waitqueue_head(&d->mem_event->access.wq);
         (void)mem_event_disable(d, &d->mem_event->access);
-    if ( d->mem_event->share.ring_page )
+    }
+    if ( d->mem_event->share.ring_page ) {
+        destroy_waitqueue_head(&d->mem_event->share.wq);
         (void)mem_event_disable(d, &d->mem_event->share);
+    }
 }
 
 int mem_event_domctl(struct domain *d, xen_domctl_mem_event_op_t *mec,

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