# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1260520948 0
# Node ID 295e77eed8c9004f3a405f7d386eee725c5ac523
# Parent 8f304c003af49d3b20aff5a6c2c963a7af696378
PoD: appropriate BUG_ON when domain is dying
BUG_ON(d->is_dying) in p2m_pod_cache_add() which is introduced in
c/s 20426 is not proper. Since dom->is_dying is set asynchronously.
For example, MMU_UPDATE hypercalls from qemu and the
DOMCTL_destroydomain hypercall from xend can be issued simultaneously.
Also this patch lets p2m_pod_empty_cache() wait by spin_barrier
until another PoD operation ceases.
Signed-off-by: Kouya Shimura <kouya@xxxxxxxxxxxxxx>
Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---
xen/arch/x86/mm/p2m.c | 25 +++++++++++++++++++++----
1 files changed, 21 insertions(+), 4 deletions(-)
diff -r 8f304c003af4 -r 295e77eed8c9 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c Wed Dec 09 10:59:31 2009 +0000
+++ b/xen/arch/x86/mm/p2m.c Fri Dec 11 08:42:28 2009 +0000
@@ -267,6 +267,8 @@ p2m_pod_cache_add(struct domain *d,
}
#endif
+ ASSERT(p2m_locked_by_me(p2md));
+
/*
* Pages from domain_alloc and returned by the balloon driver aren't
* guaranteed to be zero; but by reclaiming zero pages, we implicitly
@@ -303,7 +305,9 @@ p2m_pod_cache_add(struct domain *d,
BUG();
}
- BUG_ON(d->is_dying);
+ /* Ensure that the PoD cache has never been emptied.
+ * This may cause "zombie domains" since the page will never be freed. */
+ BUG_ON( d->arch.relmem != RELMEM_not_started );
spin_unlock(&d->page_alloc_lock);
@@ -501,6 +505,8 @@ p2m_pod_set_mem_target(struct domain *d,
int ret = 0;
unsigned long populated;
+ p2m_lock(p2md);
+
/* P == B: Nothing to do. */
if ( p2md->pod.entry_count == 0 )
goto out;
@@ -528,6 +534,8 @@ p2m_pod_set_mem_target(struct domain *d,
ret = p2m_pod_set_cache_target(d, pod_target);
out:
+ p2m_unlock(p2md);
+
return ret;
}
@@ -536,6 +544,10 @@ p2m_pod_empty_cache(struct domain *d)
{
struct p2m_domain *p2md = d->arch.p2m;
struct page_info *page;
+
+ /* After this barrier no new PoD activities can happen. */
+ BUG_ON(!d->is_dying);
+ spin_barrier(&p2md->lock);
spin_lock(&d->page_alloc_lock);
@@ -588,7 +600,7 @@ p2m_pod_decrease_reservation(struct doma
/* If we don't have any outstanding PoD entries, let things take their
* course */
- if ( p2md->pod.entry_count == 0 || unlikely(d->is_dying) )
+ if ( p2md->pod.entry_count == 0 )
goto out;
/* Figure out if we need to steal some freed memory for our cache */
@@ -596,6 +608,9 @@ p2m_pod_decrease_reservation(struct doma
p2m_lock(p2md);
audit_p2m(d);
+
+ if ( unlikely(d->is_dying) )
+ goto out_unlock;
/* See what's in here. */
/* FIXME: Add contiguous; query for PSE entries? */
@@ -1006,9 +1021,11 @@ p2m_pod_demand_populate(struct domain *d
struct p2m_domain *p2md = d->arch.p2m;
int i;
+ ASSERT(p2m_locked_by_me(d->arch.p2m));
+
/* This check is done with the p2m lock held. This will make sure that
- * even if d->is_dying changes under our feet, empty_pod_cache() won't
start
- * until we're done. */
+ * even if d->is_dying changes under our feet, p2m_pod_empty_cache()
+ * won't start until we're done. */
if ( unlikely(d->is_dying) )
goto out_fail;
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