On Mon, 9 Jun 2014, Steven Rostedt wrote:
> On Mon, 09 Jun 2014 20:28:10 -0000
> Thomas Gleixner <t...@linutronix.de> wrote:
> > /*
> > + * If we just follow the lock chain for deadlock detection, no
> > + * need to do all the requeue operations. We avoid a truckload
>
> s/We/To/
>
>
> > + * of conditinals around the various places below and just do
>
> s/ and/, /
Ok.
> > + * the minimum chain walk checks here.
> > + */
> > + if (!requeue) {
> > + /* Release the task */
> > + raw_spin_unlock_irqrestore(&task->pi_lock, flags);
> > + put_task_struct(task);
> > +
> > + /* If there is no owner of the lock, end of chain. */
> > + if (!rt_mutex_owner(lock)) {
> > + raw_spin_unlock(&lock->wait_lock);
> > + return 0;
> > + }
> > +
> > + /* Grab the next task, i.e. owner of @lock */
> > + task = rt_mutex_owner(lock);
> > + get_task_struct(task);
> > + raw_spin_lock_irqsave(&task->pi_lock, flags);
> > +
> > + /* Store whether owner is blocked itself and drop locks */
> > + next_lock = task_blocked_on(task);
> > + raw_spin_unlock_irqrestore(&task->pi_lock, flags);
> > + raw_spin_unlock(&lock->wait_lock);
> > +
> > + /* If owner is not blocked, end of chain. */
> > + if (!next_lock)
> > + goto out_put_task;
>
> On the loop back around, have something like:
>
> if (top_waiter) {
> if (!task_has_pi_waiters(task))
> goto out_unlock_pi;
The task has at least one pi waiter.
> if (!requeue &&
> top_waiter != task_top_pi_waiter(task)) {
> if (!detect_deadlock)
> goto out_unlock_pi;
> else
> requeue = false;
> }
Errm? if requeue is off we are in deadlock detection chainwalk
mode. So all we care about is whether task is blocked on
next_lock or not.
What you actually missed is that we need to read out top_waiter for
the current lock. Fixed already.
Thanks,
tglx
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