[Xen-devel] [PATCH 8 of 8] x86/mm: Avoid spurious deadlock panic trigger

[Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>]

 xen/arch/x86/mm/mm-locks.h |  3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)


In the mm layer, if we take lock A, then lock B, and the recursively lock A,
the deadlock detector panics. This is not a deadlock risk because we
already 'own' the outer lock (A), so we will not contend for that resource.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>

diff -r 2dc0ef05662e -r 409f0f368ae3 xen/arch/x86/mm/mm-locks.h
--- a/xen/arch/x86/mm/mm-locks.h
+++ b/xen/arch/x86/mm/mm-locks.h
@@ -61,7 +61,8 @@ do {                                \
 
 static inline void _mm_lock(mm_lock_t *l, const char *func, int level, int rec)
 {
-    __check_lock_level(level);
+    if ( !((mm_locked_by_me(l)) && rec) ) 
+        __check_lock_level(level);
     spin_lock_recursive(&l->lock);
     if ( l->lock.recurse_cnt == 1 )
     {

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