rwsem: Implement down_read_killable_nested

In preparation for converting exec_update_mutex to a rwsem so that
multiple readers can execute in parallel and not deadlock, add
down_read_killable_nested.  This is needed so that kcmp_lock
can be converted from working on a mutexes to working on rw_semaphores.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/87o8jabqh3.fsf@x220.int.ebiederm.org

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 25e3fde8561781ef6a54a3dfa6c4163229e88f10..13021b08b2ed6f7e540fcb7d6d7acfeb6c4063a8 100644 (file)
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -171,6 +171,7 @@ extern void downgrade_write(struct rw_semaphore *sem);
  * See Documentation/locking/lockdep-design.rst for more details.)
  */
 extern void down_read_nested(struct rw_semaphore *sem, int subclass);
+extern int __must_check down_read_killable_nested(struct rw_semaphore *sem, int subclass);
 extern void down_write_nested(struct rw_semaphore *sem, int subclass);
 extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass);
 extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock);
@@ -191,6 +192,7 @@ 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_read_killable_nested(sem, subclass)      down_read_killable(sem)
 # define down_write_nest_lock(sem, nest_lock)  down_write(sem)
 # define down_write_nested(sem, subclass)      down_write(sem)
 # define down_write_killable_nested(sem, subclass)     down_write_killable(sem)

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index f11b9bd3431d28c2d92bf63de177c6f8b51ce10a..54d11cb9755102bcb99a997a4fcae11e832be137 100644 (file)
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1605,6 +1605,20 @@ void down_read_nested(struct rw_semaphore *sem, int subclass)
 }
 EXPORT_SYMBOL(down_read_nested);
 
+int down_read_killable_nested(struct rw_semaphore *sem, int subclass)
+{
+       might_sleep();
+       rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
+
+       if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_killable)) {
+               rwsem_release(&sem->dep_map, _RET_IP_);
+               return -EINTR;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL(down_read_killable_nested);
+
 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
 {
        might_sleep();