This allows us to not rely on the KERNEL_LOCK() to check reference
counts.
Also reduces differences with NetBSD and shrink my upcoming `vmobjlock'
diff.
ok?
Index: uvm/uvm_map.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_map.c,v
retrieving revision 1.274
diff -u -p -r1.274 uvm_map.c
--- uvm/uvm_map.c 26 Mar 2021 13:40:05 -0000 1.274
+++ uvm/uvm_map.c 18 May 2021 09:36:55 -0000
@@ -491,12 +491,13 @@ uvm_mapent_addr_remove(struct vm_map *ma
/*
* uvm_map_reference: add reference to a map
*
- * XXX check map reference counter lock
+ * => map need not be locked
*/
-#define uvm_map_reference(_map)
\
- do { \
- map->ref_count++; \
- } while (0)
+void
+uvm_map_reference(struct vm_map *map)
+{
+ atomic_inc_int(&map->ref_count);
+}
/*
* Calculate the dused delta.
@@ -4292,7 +4293,7 @@ uvm_map_deallocate(vm_map_t map)
int c;
struct uvm_map_deadq dead;
- c = --map->ref_count;
+ c = atomic_dec_int_nv(&map->ref_count);
if (c > 0) {
return;
}
Index: uvm/uvm_map.h
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_map.h,v
retrieving revision 1.69
diff -u -p -r1.69 uvm_map.h
--- uvm/uvm_map.h 12 Mar 2021 14:15:49 -0000 1.69
+++ uvm/uvm_map.h 18 May 2021 09:36:36 -0000
@@ -259,6 +259,7 @@ RBT_PROTOTYPE(uvm_map_addr, vm_map_entry
* read_locks and write_locks are used in lock debugging code.
*
* Locks used to protect struct members in this file:
+ * a atomic operations
* I immutable after creation or exec(2)
* v `vm_map_lock' (this map `lock' or `mtx')
*/
@@ -272,7 +273,7 @@ struct vm_map {
struct uvm_map_addr addr; /* [v] Entry tree, by addr */
vsize_t size; /* virtual size */
- int ref_count; /* Reference count */
+ int ref_count; /* [a] Reference count */
int flags; /* flags */
struct mutex flags_lock; /* flags lock */
unsigned int timestamp; /* Version number */
