Mailing List Archive

xen/arch/x86/mm/mm-locks.h | 27 +++++++++++++++++++++++++++
1 files changed, 27 insertions(+), 0 deletions(-)


Declare an order-enforcing construct for a lock used in the mm layer
that is not of type mm_lock_t. This is useful whenever the mm layer
takes locks from other subsystems, or locks not implemented as
mm_lock_t.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>

diff -r 25b9a9966368 -r c915609e4235 xen/arch/x86/mm/mm-locks.h
--- a/xen/arch/x86/mm/mm-locks.h
+++ b/xen/arch/x86/mm/mm-locks.h
@@ -70,6 +70,18 @@ static inline void _mm_lock(mm_lock_t *l
panic("mm lock already held by %s\n", l->locker_function);
__set_lock_level(level);
}
+
+static inline void _mm_enforce_order_lock_pre(int level)
+{
+ __check_lock_level(level);
+}
+
+static inline void _mm_enforce_order_lock_post(int level, int *unlock_level)
+{
+ *unlock_level = __get_lock_level();
+ __set_lock_level(level);
+}
+
/* 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)\
@@ -78,6 +90,16 @@ static inline void _mm_lock(mm_lock_t *l
#define mm_lock(name, l) mm_lock_##name(l, __func__, 0)
#define mm_lock_recursive(name, l) mm_lock_##name(l, __func__, 1)

+/* This wrapper is intended for "external" locks which do not use
+ * the mm_lock_t types. Such locks inside the mm code are also subject
+ * to ordering constraints. They cannot be recursive (yet, additional
+ * bookkepping is necessary) */
+#define declare_mm_order_constraint(name) \
+ static inline void mm_enforce_order_lock_pre_##name(void) \
+ { _mm_enforce_order_lock_pre(__LINE__); } \
+ static inline void mm_enforce_order_lock_post_##name(int *unlock_level) \
+ { _mm_enforce_order_lock_post(__LINE__, unlock_level); } \
+
static inline void mm_unlock(mm_lock_t *l)
{
if ( l->lock.recurse_cnt == 1 )
@@ -88,6 +110,11 @@ static inline void mm_unlock(mm_lock_t *
spin_unlock_recursive(&l->lock);
}

+static inline void mm_enforce_order_unlock(int unlock_level)
+{
+ __set_lock_level(unlock_level);
+}
+
/************************************************************************
* *
* To avoid deadlocks, these locks _MUST_ be taken in the order they're *

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