[tip: locking/core] rwsem: Implement down_read_interruptible

tip-bot2 for Eric W. Biederman
2020-12-09T18:40:25Z

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

Commit-ID: 31784cff7ee073b34d6eddabb95e3be2880a425c
Gitweb: https://git.kernel.org/tip/31784cff7ee073b34d6eddabb95e3be2880a425c
Author: Eric W. Biederman <ebiederm@xmission.com>
AuthorDate: Thu, 03 Dec 2020 14:11:13 -06:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 09 Dec 2020 17:08:42 +01:00

rwsem: Implement down_read_interruptible

In preparation for converting exec_update_mutex to a rwsem so that
multiple readers can execute in parallel and not deadlock, add
down_read_interruptible. This is needed for perf_event_open to be
converted (with no semantic changes) from working on a mutex to
wroking on a rwsem.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/87k0tybqfy.fsf@x220.int.ebiederm.org
---
include/linux/rwsem.h | 1 +
kernel/locking/rwsem.c | 26 ++++++++++++++++++++++++++
2 files changed, 27 insertions(+)

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 13021b0..4c715be 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -123,6 +123,7 @@ static inline int rwsem_is_contended(struct rw_semaphore *sem)
* lock for reading
*/
extern void down_read(struct rw_semaphore *sem);
+extern int __must_check down_read_interruptible(struct rw_semaphore *sem);
extern int __must_check down_read_killable(struct rw_semaphore *sem);

/*
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 54d11cb..a163542 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1345,6 +1345,18 @@ static inline void __down_read(struct rw_semaphore *sem)
}
}

+static inline int __down_read_interruptible(struct rw_semaphore *sem)
+{
+ if (!rwsem_read_trylock(sem)) {
+ if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE)))
+ return -EINTR;
+ DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
+ } else {
+ rwsem_set_reader_owned(sem);
+ }
+ return 0;
+}
+
static inline int __down_read_killable(struct rw_semaphore *sem)
{
if (!rwsem_read_trylock(sem)) {
@@ -1495,6 +1507,20 @@ void __sched down_read(struct rw_semaphore *sem)
}
EXPORT_SYMBOL(down_read);

+int __sched down_read_interruptible(struct rw_semaphore *sem)
+{
+ might_sleep();
+ rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
+
+ if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) {
+ rwsem_release(&sem->dep_map, _RET_IP_);
+ return -EINTR;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(down_read_interruptible);
+
int __sched down_read_killable(struct rw_semaphore *sem)
{
might_sleep();