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rwsem: move rwsem_down_failed_common code into rwsem_down_{read,write}_failed 

Remove the rwsem_down_failed_common function and replace it with two
identical copies of its code in rwsem_down_{read,write}_failed.

This is because we want to make different optimizations in
rwsem_down_{read,write}_failed; we are adding this pure-duplication
step as a separate commit in order to make it easier to check the
following steps.

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>
This commit is contained in:
Michel Lespinasse 2013-05-07 06:45:51 -07:00 committed by Linus Torvalds
parent f7dd1cee9a
commit 1e78277ccb
1 changed files with 57 additions and 15 deletions
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72
lib/rwsem.c
View File

@ -178,12 +178,12 @@ try_again_write:
}
/*
* wait for a lock to be granted
* wait for the read lock to be granted
*/
static struct rw_semaphore __sched *
rwsem_down_failed_common(struct rw_semaphore *sem,
enum rwsem_waiter_type type, signed long adjustment)
struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
{
enum rwsem_waiter_type type = RWSEM_WAITING_FOR_READ;
signed long adjustment = -RWSEM_ACTIVE_READ_BIAS;
struct rwsem_waiter waiter;
struct task_struct *tsk = current;
signed long count;
@ -237,22 +237,64 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
return sem;
}
/*
* wait for the read lock to be granted
*/
struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
{
return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_READ,
-RWSEM_ACTIVE_READ_BIAS);
}
/*
* wait for the write lock to be granted
*/
struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
{
return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_WRITE,
-RWSEM_ACTIVE_WRITE_BIAS);
enum rwsem_waiter_type type = RWSEM_WAITING_FOR_WRITE;
signed long adjustment = -RWSEM_ACTIVE_WRITE_BIAS;
struct rwsem_waiter waiter;
struct task_struct *tsk = current;
signed long count;
/* set up my own style of waitqueue */
waiter.task = tsk;
waiter.type = type;
get_task_struct(tsk);
raw_spin_lock_irq(&sem->wait_lock);
if (list_empty(&sem->wait_list))
adjustment += RWSEM_WAITING_BIAS;
list_add_tail(&waiter.list, &sem->wait_list);
/* we're now waiting on the lock, but no longer actively locking */
count = rwsem_atomic_update(adjustment, sem);
/* If there are no active locks, wake the front queued process(es) up.
*
* Alternatively, if we're called from a failed down_write(), there
* were already threads queued before us and there are no active
* writers, the lock must be read owned; so we try to wake any read
* locks that were queued ahead of us. */
if (count == RWSEM_WAITING_BIAS)
sem = __rwsem_do_wake(sem, RWSEM_WAKE_NO_ACTIVE);
else if (count > RWSEM_WAITING_BIAS &&
adjustment == -RWSEM_ACTIVE_WRITE_BIAS)
sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);
raw_spin_unlock_irq(&sem->wait_lock);
/* wait to be given the lock */
while (true) {
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
if (!waiter.task)
break;
raw_spin_lock_irq(&sem->wait_lock);
/* Try to get the writer sem, may steal from the head writer: */
if (type == RWSEM_WAITING_FOR_WRITE)
if (try_get_writer_sem(sem, &waiter)) {
raw_spin_unlock_irq(&sem->wait_lock);
return sem;
}
raw_spin_unlock_irq(&sem->wait_lock);
schedule();
}
tsk->state = TASK_RUNNING;
return sem;
}
/*