rwsem: make the waiter type an enumeration rather than a bitmask

We are not planning to add some new waiter flags, so we can convert the
waiter type into an enumeration.

Background: David Howells suggested I do this back when I tried adding
a new waiter type for unfair readers. However, I believe the cleanup
applies regardless of that use case.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 8 deletions

diff --git a/lib/rwsem-spinlock.c b/lib/rwsem-spinlock.c
index 7542afbb22b3..5f117f37ac0a 100644
--- a/lib/rwsem-spinlock.c
+++ b/lib/rwsem-spinlock.c
@@ -9,12 +9,15 @@
 #include <linux/sched.h>
 #include <linux/export.h>
 
+enum rwsem_waiter_type {
+        RWSEM_WAITING_FOR_WRITE,
+        RWSEM_WAITING_FOR_READ
+};
+
 struct rwsem_waiter {
         struct list_head list;
         struct task_struct *task;
-        unsigned int flags;
-#define RWSEM_WAITING_FOR_READ  0x00000001
-#define RWSEM_WAITING_FOR_WRITE 0x00000002
+        enum rwsem_waiter_type type;
 };
 
 int rwsem_is_locked(struct rw_semaphore *sem)
@@ -68,7 +71,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
         waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
 
         if (!wakewrite) {
-                if (waiter->flags & RWSEM_WAITING_FOR_WRITE)
+                if (waiter->type == RWSEM_WAITING_FOR_WRITE)
                         goto out;
                 goto dont_wake_writers;
         }
@@ -78,7 +81,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
          * to -1 here to indicate we get the lock. Instead, we wake it up
          * to let it go get it again.
          */
-        if (waiter->flags & RWSEM_WAITING_FOR_WRITE) {
+        if (waiter->type == RWSEM_WAITING_FOR_WRITE) {
                 wake_up_process(waiter->task);
                 goto out;
         }
@@ -86,7 +89,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
         /* grant an infinite number of read locks to the front of the queue */
  dont_wake_writers:
         woken = 0;
-        while (waiter->flags & RWSEM_WAITING_FOR_READ) {
+        while (waiter->type == RWSEM_WAITING_FOR_READ) {
                 struct list_head *next = waiter->list.next;
 
                 list_del(&waiter->list);
@@ -144,7 +147,7 @@ void __sched __down_read(struct rw_semaphore *sem)
 
         /* set up my own style of waitqueue */
         waiter.task = tsk;
-        waiter.flags = RWSEM_WAITING_FOR_READ;
+        waiter.type = RWSEM_WAITING_FOR_READ;
         get_task_struct(tsk);
 
         list_add_tail(&waiter.list, &sem->wait_list);
@@ -201,7 +204,7 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
         /* set up my own style of waitqueue */
         tsk = current;
         waiter.task = tsk;
-        waiter.flags = RWSEM_WAITING_FOR_WRITE;
+        waiter.type = RWSEM_WAITING_FOR_WRITE;
         list_add_tail(&waiter.list, &sem->wait_list);
 
         /* wait for someone to release the lock */