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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>
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parent
f7dd1cee9a
commit
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1 changed files with 57 additions and 15 deletions
72
lib/rwsem.c
72
lib/rwsem.c
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@ -178,12 +178,12 @@ static int try_get_writer_sem(struct rw_semaphore *sem,
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}
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}
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/*
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/*
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* wait for a lock to be granted
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* wait for the read lock to be granted
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*/
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*/
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static struct rw_semaphore __sched *
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struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
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rwsem_down_failed_common(struct rw_semaphore *sem,
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enum rwsem_waiter_type type, signed long adjustment)
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{
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{
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enum rwsem_waiter_type type = RWSEM_WAITING_FOR_READ;
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signed long adjustment = -RWSEM_ACTIVE_READ_BIAS;
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struct rwsem_waiter waiter;
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struct rwsem_waiter waiter;
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struct task_struct *tsk = current;
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struct task_struct *tsk = current;
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signed long count;
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signed long count;
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@ -237,22 +237,64 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
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return sem;
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return sem;
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}
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}
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/*
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* wait for the read lock to be granted
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*/
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struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
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{
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return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_READ,
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-RWSEM_ACTIVE_READ_BIAS);
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}
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/*
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/*
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* wait for the write lock to be granted
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* wait for the write lock to be granted
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*/
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*/
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struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
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struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
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{
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{
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return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_WRITE,
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enum rwsem_waiter_type type = RWSEM_WAITING_FOR_WRITE;
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-RWSEM_ACTIVE_WRITE_BIAS);
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signed long adjustment = -RWSEM_ACTIVE_WRITE_BIAS;
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struct rwsem_waiter waiter;
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struct task_struct *tsk = current;
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signed long count;
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/* set up my own style of waitqueue */
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waiter.task = tsk;
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waiter.type = type;
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get_task_struct(tsk);
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raw_spin_lock_irq(&sem->wait_lock);
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if (list_empty(&sem->wait_list))
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adjustment += RWSEM_WAITING_BIAS;
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list_add_tail(&waiter.list, &sem->wait_list);
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/* we're now waiting on the lock, but no longer actively locking */
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count = rwsem_atomic_update(adjustment, sem);
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/* If there are no active locks, wake the front queued process(es) up.
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*
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* Alternatively, if we're called from a failed down_write(), there
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* were already threads queued before us and there are no active
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* writers, the lock must be read owned; so we try to wake any read
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* locks that were queued ahead of us. */
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if (count == RWSEM_WAITING_BIAS)
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sem = __rwsem_do_wake(sem, RWSEM_WAKE_NO_ACTIVE);
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else if (count > RWSEM_WAITING_BIAS &&
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adjustment == -RWSEM_ACTIVE_WRITE_BIAS)
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sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);
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raw_spin_unlock_irq(&sem->wait_lock);
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/* wait to be given the lock */
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while (true) {
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set_task_state(tsk, TASK_UNINTERRUPTIBLE);
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if (!waiter.task)
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break;
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raw_spin_lock_irq(&sem->wait_lock);
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/* Try to get the writer sem, may steal from the head writer: */
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if (type == RWSEM_WAITING_FOR_WRITE)
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if (try_get_writer_sem(sem, &waiter)) {
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raw_spin_unlock_irq(&sem->wait_lock);
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return sem;
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}
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raw_spin_unlock_irq(&sem->wait_lock);
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schedule();
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}
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tsk->state = TASK_RUNNING;
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return sem;
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}
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}
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/*
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/*
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