percpu-rwsem: introduce percpu_rwsem_release() and percpu_rwsem_acquire()

Add percpu_rwsem_release() and percpu_rwsem_acquire() for the users
which need to return to userspace with percpu-rwsem lock held and/or
pass the ownership to another thread.

TODO: change percpu_rwsem_release() to use rwsem_clear_owner(). We can
either fold kernel/locking/rwsem.h into include/linux/rwsem.h, or add
the non-inline percpu_rwsem_clear_owner().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index 16c30cd33501390094c7eec3b4ccf6321c01963f..834c4e52cb2d1cab57ba33a3e87c025bc7e4a7cc 100644 (file)
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -32,4 +32,23 @@ extern void percpu_free_rwsem(struct percpu_rw_semaphore *);
        __percpu_init_rwsem(brw, #brw, &rwsem_key);             \
 })
 
+
+#define percpu_rwsem_is_held(sem) lockdep_is_held(&(sem)->rw_sem)
+
+static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
+                                       bool read, unsigned long ip)
+{
+       lock_release(&sem->rw_sem.dep_map, 1, ip);
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+       if (!read)
+               sem->rw_sem.owner = NULL;
+#endif
+}
+
+static inline void percpu_rwsem_acquire(struct percpu_rw_semaphore *sem,
+                                       bool read, unsigned long ip)
+{
+       lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
+}
+
 #endif