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authorMichel Lespinasse <walken@google.com>2013-05-07 06:45:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-07 07:20:15 -0700
commite2d57f782c8a906f80d5b5f54da803c1638929d7 (patch)
tree96a3d2f26b8257d39db40ec4cd3cd52b3ef14588 /lib
parentc1be5a5b1b355d40e6cf79cc979eb66dafa24ad1 (diff)
downloadlinux-linaro-stable-e2d57f782c8a906f80d5b5f54da803c1638929d7.tar.gz
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>
Diffstat (limited to 'lib')
-rw-r--r--lib/rwsem-spinlock.c19
-rw-r--r--lib/rwsem.c23
2 files changed, 24 insertions, 18 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 */
diff --git a/lib/rwsem.c b/lib/rwsem.c
index ad5e0df16ab4..672eb33218ac 100644
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -30,12 +30,15 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
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 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
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 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
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 @@ static int try_get_writer_sem(struct rw_semaphore *sem,
/* 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 @@ try_again_write:
*/
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 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
/* 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 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
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;