Mailing List Archive

xen/arch/x86/mm/mm-locks.h | 27 +++++++++++++++++++--------
1 files changed, 19 insertions(+), 8 deletions(-)


The mm layer has a construct to enforce locks are taken in a pre-
defined order, and thus avert deadlock. Refactor pieces of this
code for later use, no functional changes.

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

diff -r a33af75083c7 -r 25b9a9966368 xen/arch/x86/mm/mm-locks.h
--- a/xen/arch/x86/mm/mm-locks.h
+++ b/xen/arch/x86/mm/mm-locks.h
@@ -28,6 +28,7 @@

/* Per-CPU variable for enforcing the lock ordering */
DECLARE_PER_CPU(int, mm_lock_level);
+#define __get_lock_level() (this_cpu(mm_lock_level))

static inline void mm_lock_init(mm_lock_t *l)
{
@@ -42,22 +43,32 @@ static inline int mm_locked_by_me(mm_loc
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. */
+#define __check_lock_level(l) \
+do { \
+ if ( unlikely(__get_lock_level()) > (l) ) \
+ panic("mm locking order violation: %i > %i\n", \
+ __get_lock_level(), (l)); \
+} while(0)
+
+#define __set_lock_level(l) \
+do { \
+ __get_lock_level() = (l); \
+} while(0)
+
static inline void _mm_lock(mm_lock_t *l, const char *func, int level, int rec)
{
- /* If you see this crash, the numbers printed are lines in this file
- * where the offending locks are declared. */
- if ( unlikely(this_cpu(mm_lock_level) > level) )
- panic("mm locking order violation: %i > %i\n",
- this_cpu(mm_lock_level), level);
+ __check_lock_level(level);
spin_lock_recursive(&l->lock);
if ( l->lock.recurse_cnt == 1 )
{
l->locker_function = func;
- l->unlock_level = this_cpu(mm_lock_level);
+ l->unlock_level = __get_lock_level();
}
else if ( (unlikely(!rec)) )
panic("mm lock already held by %s\n", l->locker_function);
- this_cpu(mm_lock_level) = level;
+ __set_lock_level(level);
}
/* This wrapper uses the line number to express the locking order below */
#define declare_mm_lock(name) \
@@ -72,7 +83,7 @@ static inline void mm_unlock(mm_lock_t *
if ( l->lock.recurse_cnt == 1 )
{
l->locker_function = "nobody";
- this_cpu(mm_lock_level) = l->unlock_level;
+ __set_lock_level(l->unlock_level);
}
spin_unlock_recursive(&l->lock);
}

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel