[tip: locking/core] rwsem: Implement down_read_killable_nested

From: tip-bot2 for Eric W. Biederman
Date: Wed Dec 09 2020 - 13:41:39 EST


The following commit has been merged into the locking/core branch of tip:

Commit-ID: 0f9368b5bf6db0c04afc5454b1be79022a681615
Gitweb: https://git.kernel.org/tip/0f9368b5bf6db0c04afc5454b1be79022a681615
Author: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
AuthorDate: Thu, 03 Dec 2020 14:10:32 -06:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 09 Dec 2020 17:08:41 +01:00

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@xxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/87o8jabqh3.fsf@xxxxxxxxxxxxxxxxxxxxx
---
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 25e3fde..13021b0 100644
--- 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 f11b9bd..54d11cb 100644
--- 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();