[Xen-changelog] [xen-unstable] x86/mm: Fix p2m teardown locking

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
# Date 1327584087 0
# Node ID f6c33cfe7333a12f6792e6ce15ddf70818508cea
# Parent  4e52d39fdb25914ac15aef62129e95b645166b24
x86/mm: Fix p2m teardown locking

Holding the p2m lock during a p2m teardown, while unsharing entries pointing to
shared frames, causes a locking inversion and deadlock panic.

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


diff -r 4e52d39fdb25 -r f6c33cfe7333 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c     Thu Jan 26 13:21:27 2012 +0000
+++ b/xen/arch/x86/mm/p2m.c     Thu Jan 26 13:21:27 2012 +0000
@@ -343,8 +343,6 @@
     if (p2m == NULL)
         return;
 
-    p2m_lock(p2m);
-
 #ifdef __x86_64__
     for ( gfn=0; gfn < p2m->max_mapped_pfn; gfn++ )
     {
@@ -358,6 +356,8 @@
     }
 #endif
 
+    p2m_lock(p2m);
+
     p2m->phys_table = pagetable_null();
 
     while ( (pg = page_list_remove_head(&p2m->pages)) )

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