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

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 13021b0..4c715be 100644 (file)
--- 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 (file)
--- 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();