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    Subject[PATCH 06/10] rwsem: smaller wrappers around rwsem_down_failed_common
    Date
    More code can be pushed from rwsem_down_read_failed and
    rwsem_down_write_failed into rwsem_down_failed_common.

    Following change adding down_read_unfair infrastructure support also
    enjoys having flags available in a register rather than having to
    fish it out in the struct rwsem_waiter...

    Signed-off-by: Michel Lespinasse <walken@google.com>
    ---
    lib/rwsem.c | 25 ++++++++++---------------
    1 files changed, 10 insertions(+), 15 deletions(-)

    diff --git a/lib/rwsem.c b/lib/rwsem.c
    index 89cd8b3..d8764e0 100644
    --- a/lib/rwsem.c
    +++ b/lib/rwsem.c
    @@ -171,8 +171,9 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
    */
    static struct rw_semaphore __sched *
    rwsem_down_failed_common(struct rw_semaphore *sem,
    - struct rwsem_waiter *waiter, signed long adjustment)
    + unsigned int flags, signed long adjustment)
    {
    + struct rwsem_waiter waiter;
    struct task_struct *tsk = current;
    signed long count;

    @@ -180,12 +181,13 @@ rwsem_down_failed_common(struct rw_semaphore *sem,

    /* set up my own style of waitqueue */
    spin_lock_irq(&sem->wait_lock);
    - waiter->task = tsk;
    + waiter.task = tsk;
    + waiter.flags = flags;
    get_task_struct(tsk);

    if (list_empty(&sem->wait_list))
    adjustment += RWSEM_WAITING_BIAS;
    - list_add_tail(&waiter->list, &sem->wait_list);
    + 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);
    @@ -206,7 +208,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem,

    /* wait to be given the lock */
    for (;;) {
    - if (!waiter->task)
    + if (!waiter.task)
    break;
    schedule();
    set_task_state(tsk, TASK_UNINTERRUPTIBLE);
    @@ -223,11 +225,8 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
    asmregparm struct rw_semaphore __sched *
    rwsem_down_read_failed(struct rw_semaphore *sem)
    {
    - struct rwsem_waiter waiter;
    -
    - waiter.flags = RWSEM_WAITING_FOR_READ;
    - rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_READ_BIAS);
    - return sem;
    + return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_READ,
    + -RWSEM_ACTIVE_READ_BIAS);
    }

    /*
    @@ -236,12 +235,8 @@ rwsem_down_read_failed(struct rw_semaphore *sem)
    asmregparm struct rw_semaphore __sched *
    rwsem_down_write_failed(struct rw_semaphore *sem)
    {
    - struct rwsem_waiter waiter;
    -
    - waiter.flags = RWSEM_WAITING_FOR_WRITE;
    - rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_WRITE_BIAS);
    -
    - return sem;
    + return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_WRITE,
    + -RWSEM_ACTIVE_WRITE_BIAS);
    }

    /*
    --
    1.7.0.1


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