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-rw-r--r--include/linux/rwsem.h10
-rw-r--r--kernel/rwsem.c16
2 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 8da67d6..0616ffe 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -133,10 +133,20 @@ do { \
_down_write_nest_lock(sem, &(nest_lock)->dep_map); \
} while (0);
+/*
+ * Take/release a lock when not the owner will release it.
+ *
+ * [ This API should be avoided as much as possible - the
+ * proper abstraction for this case is completions. ]
+ */
+extern void down_read_non_owner(struct rw_semaphore *sem);
+extern void up_read_non_owner(struct rw_semaphore *sem);
#else
# define down_read_nested(sem, subclass) down_read(sem)
# define down_write_nest_lock(sem, nest_lock) down_write(sem)
# define down_write_nested(sem, subclass) down_write(sem)
+# define down_read_non_owner(sem) down_read(sem)
+# define up_read_non_owner(sem) up_read(sem)
#endif
#endif /* _LINUX_RWSEM_H */
diff --git a/kernel/rwsem.c b/kernel/rwsem.c
index b3c6c3f..cfff143 100644
--- a/kernel/rwsem.c
+++ b/kernel/rwsem.c
@@ -126,6 +126,15 @@ void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
EXPORT_SYMBOL(_down_write_nest_lock);
+void down_read_non_owner(struct rw_semaphore *sem)
+{
+ might_sleep();
+
+ __down_read(sem);
+}
+
+EXPORT_SYMBOL(down_read_non_owner);
+
void down_write_nested(struct rw_semaphore *sem, int subclass)
{
might_sleep();
@@ -136,6 +145,13 @@ void down_write_nested(struct rw_semaphore *sem, int subclass)
EXPORT_SYMBOL(down_write_nested);
+void up_read_non_owner(struct rw_semaphore *sem)
+{
+ __up_read(sem);
+}
+
+EXPORT_SYMBOL(up_read_non_owner);
+
#endif
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