On 04/26/2010 06:37 PM, Mel Gorman wrote:
diff --git a/mm/rmap.c b/mm/rmap.c
index 85f203e..bc313a6 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1368,15 +1368,31 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
* are holding mmap_sem. Users without mmap_sem are required to
* take a reference count to prevent the anon_vma disappearing
*/
+retry:
anon_vma = page_anon_vma(page);
if (!anon_vma)
return ret;
spin_lock(&anon_vma->lock);
list_for_each_entry(avc,&anon_vma->head, same_anon_vma) {
struct vm_area_struct *vma = avc->vma;
- unsigned long address = vma_address(page, vma);
- if (address == -EFAULT)
- continue;
+ unsigned long address;
+
+ /*
+ * Guard against deadlocks by not spinning against
+ * vma->anon_vma->lock. If contention is found, release our
+ * lock and try again until VMA list can be traversed without
+ * contention.
+ */
+ if (anon_vma != vma->anon_vma) {
+ if (!spin_trylock(&vma->anon_vma->lock)) {
+ spin_unlock(&anon_vma->lock);
+ goto retry;
+ }
+ }
If you're part way down the list, surely you'll need to
unlock multiple anon_vmas here before going to retry?
Otherwise you could forget to unlock one that you already
locked, and live-lock here.
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