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>
diff --git a/lib/rwsem.c b/lib/rwsem.c
index ad5e0df..672eb33 100644
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -30,12 +30,15 @@
EXPORT_SYMBOL(__init_rwsem);
+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;
};
/* Wake types for __rwsem_do_wake(). Note that RWSEM_WAKE_NO_ACTIVE and
@@ -65,7 +68,7 @@
signed long woken, loop, adjustment;
waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
- if (!(waiter->flags & RWSEM_WAITING_FOR_WRITE))
+ if (waiter->type != RWSEM_WAITING_FOR_WRITE)
goto readers_only;
if (wake_type == RWSEM_WAKE_READ_OWNED)
@@ -112,10 +115,10 @@
waiter = list_entry(waiter->list.next,
struct rwsem_waiter, list);
- } while (waiter->flags & RWSEM_WAITING_FOR_READ);
+ } while (waiter->type != RWSEM_WAITING_FOR_WRITE);
adjustment = woken * RWSEM_ACTIVE_READ_BIAS;
- if (waiter->flags & RWSEM_WAITING_FOR_READ)
+ if (waiter->type != RWSEM_WAITING_FOR_WRITE)
/* hit end of list above */
adjustment -= RWSEM_WAITING_BIAS;
@@ -148,7 +151,7 @@
/* only steal when first waiter is writing */
fwaiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
- if (!(fwaiter->flags & RWSEM_WAITING_FOR_WRITE))
+ if (fwaiter->type != RWSEM_WAITING_FOR_WRITE)
return 0;
adjustment = RWSEM_ACTIVE_WRITE_BIAS;
@@ -179,7 +182,7 @@
*/
static struct rw_semaphore __sched *
rwsem_down_failed_common(struct rw_semaphore *sem,
- unsigned int flags, signed long adjustment)
+ enum rwsem_waiter_type type, signed long adjustment)
{
struct rwsem_waiter waiter;
struct task_struct *tsk = current;
@@ -190,7 +193,7 @@
/* set up my own style of waitqueue */
raw_spin_lock_irq(&sem->wait_lock);
waiter.task = tsk;
- waiter.flags = flags;
+ waiter.type = type;
get_task_struct(tsk);
if (list_empty(&sem->wait_list))
@@ -221,7 +224,7 @@
raw_spin_lock_irq(&sem->wait_lock);
/* Try to get the writer sem, may steal from the head writer: */
- if (flags == RWSEM_WAITING_FOR_WRITE)
+ if (type == RWSEM_WAITING_FOR_WRITE)
if (try_get_writer_sem(sem, &waiter)) {
raw_spin_unlock_irq(&sem->wait_lock);
return sem;