[PATCH 5.4 10/13] rwsem: Implement down_read_killable_nested

Greg Kroah-Hartman
2021-01-07T14:33:28Z

From: Eric W. Biederman <ebiederm@xmission.com>

[ Upstream commit 0f9368b5bf6db0c04afc5454b1be79022a681615 ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/rwsem.h | 2 ++
kernel/locking/rwsem.c | 14 ++++++++++++++
2 files changed, 16 insertions(+)

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 00d6054687dd2..c91ac00d1ff8c 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -173,6 +173,7 @@ 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);
@@ -193,6 +194,7 @@ 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 baafa1dd9fcc4..2ce13f9585779 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1608,6 +1608,20 @@ 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();
--
2.27.0