[PATCH v2 3/6] mm: Use statically defined locking order

[Ross Lagerwall <ross.lagerwall@citrix.com>]

Instead of using a locking order based on line numbers which interacts
poorly with trying to create a live patch, statically define the locking
order.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
---

Changes in v2:
* Rearranged defines.
* Make lock orders fit in a sign-extended 8-bit immediate.

 xen/arch/x86/mm/mm-locks.h | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/mm/mm-locks.h b/xen/arch/x86/mm/mm-locks.h
index 74fdfc1..e5fceb2 100644
--- a/xen/arch/x86/mm/mm-locks.h
+++ b/xen/arch/x86/mm/mm-locks.h
@@ -46,8 +46,10 @@ static inline int mm_locked_by_me(mm_lock_t *l)
     return (l->lock.recurse_cpu == current->processor);
 }
 
-/* If you see this crash, the numbers printed are lines in this file 
- * where the offending locks are declared. */
+/*
+ * If you see this crash, the numbers printed are order levels defined
+ * in this file.
+ */
 #define __check_lock_level(l)                           \
 do {                                                    \
     if ( unlikely(__get_lock_level() > (l)) )           \
@@ -152,12 +154,12 @@ static inline void mm_read_unlock(mm_rwlock_t *l)
 /* This wrapper uses the line number to express the locking order below */
 #define declare_mm_lock(name)                                                 \
     static inline void mm_lock_##name(mm_lock_t *l, const char *func, int rec)\
-    { _mm_lock(l, func, __LINE__, rec); }
+    { _mm_lock(l, func, MM_LOCK_ORDER_##name, rec); }
 #define declare_mm_rwlock(name)                                               \
     static inline void mm_write_lock_##name(mm_rwlock_t *l, const char *func) \
-    { _mm_write_lock(l, func, __LINE__); }                                    \
+    { _mm_write_lock(l, func, MM_LOCK_ORDER_##name); }                                    \
     static inline void mm_read_lock_##name(mm_rwlock_t *l)                    \
-    { _mm_read_lock(l, __LINE__); }
+    { _mm_read_lock(l, MM_LOCK_ORDER_##name); }
 /* These capture the name of the calling function */
 #define mm_lock(name, l) mm_lock_##name(l, __func__, 0)
 #define mm_lock_recursive(name, l) mm_lock_##name(l, __func__, 1)
@@ -169,10 +171,10 @@ static inline void mm_read_unlock(mm_rwlock_t *l)
  * to ordering constraints. */
 #define declare_mm_order_constraint(name)                                   \
     static inline void mm_enforce_order_lock_pre_##name(void)               \
-    { _mm_enforce_order_lock_pre(__LINE__); }                               \
+    { _mm_enforce_order_lock_pre(MM_LOCK_ORDER_##name); }                               \
     static inline void mm_enforce_order_lock_post_##name(                   \
                         int *unlock_level, unsigned short *recurse_count)   \
-    { _mm_enforce_order_lock_post(__LINE__, unlock_level, recurse_count); } \
+    { _mm_enforce_order_lock_post(MM_LOCK_ORDER_##name, unlock_level, recurse_count); } \
 
 static inline void mm_unlock(mm_lock_t *l)
 {
@@ -201,8 +203,8 @@ static inline void mm_enforce_order_unlock(int unlock_level,
 
 /************************************************************************
  *                                                                      *
- * To avoid deadlocks, these locks _MUST_ be taken in the order they're *
- * declared in this file.  The locking functions will enforce this.     *
+ * To avoid deadlocks, these locks _MUST_ be taken in the order listed  *
+ * below.  The locking functions will enforce this.                     *
  *                                                                      *
  ************************************************************************/
 
@@ -214,6 +216,7 @@ static inline void mm_enforce_order_unlock(int unlock_level,
  * - setting the "cr3" field of any p2m table to a non-P2M_BASE_EAADR value.
  *   (i.e. assigning a p2m table to be the shadow of that cr3 */
 
+#define MM_LOCK_ORDER_nestedp2m               8
 declare_mm_lock(nestedp2m)
 #define nestedp2m_lock(d)   mm_lock(nestedp2m, &(d)->arch.nested_p2m_lock)
 #define nestedp2m_unlock(d) mm_unlock(&(d)->arch.nested_p2m_lock)
@@ -240,6 +243,7 @@ declare_mm_lock(nestedp2m)
  * the altp2mlist lock in the middle.
  */
 
+#define MM_LOCK_ORDER_p2m                    16
 declare_mm_rwlock(p2m);
 
 /* Sharing per page lock
@@ -251,6 +255,7 @@ declare_mm_rwlock(p2m);
  *
  * The lock is recursive because during share we lock two pages. */
 
+#define MM_LOCK_ORDER_per_page_sharing       24
 declare_mm_order_constraint(per_page_sharing)
 #define page_sharing_mm_pre_lock()   mm_enforce_order_lock_pre_per_page_sharing()
 #define page_sharing_mm_post_lock(l, r) \
@@ -265,6 +270,7 @@ declare_mm_order_constraint(per_page_sharing)
  * in the target domain must be paused.
  */
 
+#define MM_LOCK_ORDER_altp2mlist             32
 declare_mm_lock(altp2mlist)
 #define altp2m_list_lock(d)   mm_lock(altp2mlist, &(d)->arch.altp2m_list_lock)
 #define altp2m_list_unlock(d) mm_unlock(&(d)->arch.altp2m_list_lock)
@@ -279,6 +285,7 @@ declare_mm_lock(altp2mlist)
  * up a gfn and later mutate it.
  */
 
+#define MM_LOCK_ORDER_altp2m                 40
 declare_mm_rwlock(altp2m);
 #define p2m_lock(p)                             \
     do {                                        \
@@ -307,6 +314,7 @@ declare_mm_rwlock(altp2m);
  * Protects private PoD data structs: entry and cache
  * counts, page lists, sweep parameters. */
 
+#define MM_LOCK_ORDER_pod                    48
 declare_mm_lock(pod)
 #define pod_lock(p)           mm_lock(pod, &(p)->pod.lock)
 #define pod_unlock(p)         mm_unlock(&(p)->pod.lock)
@@ -319,6 +327,7 @@ declare_mm_lock(pod)
  * the ordering which we enforce here.
  * The lock is not recursive. */
 
+#define MM_LOCK_ORDER_page_alloc             56
 declare_mm_order_constraint(page_alloc)
 #define page_alloc_mm_pre_lock()   mm_enforce_order_lock_pre_page_alloc()
 #define page_alloc_mm_post_lock(l) mm_enforce_order_lock_post_page_alloc(&(l), NULL)
@@ -339,6 +348,7 @@ declare_mm_order_constraint(page_alloc)
  * It also protects the log-dirty bitmap from concurrent accesses (and
  * teardowns, etc). */
 
+#define MM_LOCK_ORDER_paging                 64
 declare_mm_lock(paging)
 #define paging_lock(d)         mm_lock(paging, &(d)->arch.paging.lock)
 #define paging_lock_recursive(d) \
-- 
2.7.4


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