Re: [patch 6/6] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
On Wed, 28 May 2014 11:43:16 +0200 (CEST) Thomas Gleixner wrote: [snip] > > > > In the above case, could we go 1 step further and avoid taking the pi > > lock as well? [snip] > > Indeed. > > Are you going to repost this patch? I'd like to review that one instead of this one if you're going to make such a charge. Thanks, -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 6/6] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
On Wed, 28 May 2014 11:43:16 +0200 (CEST) Thomas Gleixner t...@linutronix.de wrote: [snip] In the above case, could we go 1 step further and avoid taking the pi lock as well? [snip] Indeed. Are you going to repost this patch? I'd like to review that one instead of this one if you're going to make such a charge. Thanks, -- Steve -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 6/6] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
On Tue, 27 May 2014, Jason Low wrote:
> On Wed, May 21, 2014 at 8:25 PM, Thomas Gleixner wrote:
>
> > @@ -440,32 +452,41 @@ static int rt_mutex_adjust_prio_chain(st
> > get_task_struct(task);
> > raw_spin_lock_irqsave(>pi_lock, flags);
> >
> > - if (waiter == rt_mutex_top_waiter(lock)) {
> > - /*
> > -* The waiter became the top waiter on the
> > -* lock. Remove the previous top waiter from the tasks
> > -* pi waiters list and add waiter to it.
> > -*/
> > - rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
> > - rt_mutex_enqueue_pi(task, waiter);
> > - __rt_mutex_adjust_prio(task);
> > -
> > - } else if (prerequeue_top_waiter == waiter) {
> > - /*
> > -* The waiter was the top waiter on the lock. Remove
> > -* waiter from the tasks pi waiters list and add the
> > -* new top waiter to it.
> > -*/
> > - rt_mutex_dequeue_pi(task, waiter);
> > - waiter = rt_mutex_top_waiter(lock);
> > - rt_mutex_enqueue_pi(task, waiter);
> > - __rt_mutex_adjust_prio(task);
> > -
> > - } else {
> > - /*
> > -* Nothing changed. No need to do any priority
> > -* adjustment.
> > -*/
> > + /*
> > +* In case we are just following the lock chain for deadlock
> > +* detection we can avoid the whole requeue and priority
> > +* adjustment business.
> > +*/
> > + if (requeue) {
> > + if (waiter == rt_mutex_top_waiter(lock)) {
> > + /*
> > +* The waiter became the top waiter on the
> > +* lock. Remove the previous top waiter from
> > +* the tasks pi waiters list and add waiter to
> > +* it.
> > +*/
> > + rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
> > + rt_mutex_enqueue_pi(task, waiter);
> > + __rt_mutex_adjust_prio(task);
> > +
> > + } else if (prerequeue_top_waiter == waiter) {
> > + /*
> > +* The waiter was the top waiter on the
> > +* lock. Remove waiter from the tasks pi
> > +* waiters list and add the new top waiter to
> > +* it.
> > +*/
> > + rt_mutex_dequeue_pi(task, waiter);
> > + waiter = rt_mutex_top_waiter(lock);
> > + rt_mutex_enqueue_pi(task, waiter);
> > + __rt_mutex_adjust_prio(task);
> > +
> > + } else {
> > + /*
> > +* Nothing changed. No need to do any priority
> > +* adjustment.
> > +*/
> > + }
> > }
> >
> > raw_spin_unlock_irqrestore(>pi_lock, flags);
>
> In the above case, could we go 1 step further and avoid taking the pi
> lock as well?
>
> if (requeue) {
> raw_spin_lock_irqsave(>pi_lock, flags);
>
> if (waiter == rt_mutex_top_waiter(lock)) {
> /*
> * The waiter became the top waiter on the
> * lock. Remove the previous top waiter from
> * the tasks pi waiters list and add waiter to
> * it.
> */
> rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
> rt_mutex_enqueue_pi(task, waiter);
> __rt_mutex_adjust_prio(task);
>
> } else if (prerequeue_top_waiter == waiter) {
> /*
> * The waiter was the top waiter on the
> * lock. Remove waiter from the tasks pi
> * waiters list and add the new top waiter to
> * it.
> */
> rt_mutex_dequeue_pi(task, waiter);
> waiter = rt_mutex_top_waiter(lock);
> rt_mutex_enqueue_pi(task, waiter);
> __rt_mutex_adjust_prio(task);
>
> } else {
> /*
> * Nothing changed. No need to do any priority
> * adjustment.
> */
> }
>
> raw_spin_unlock_irqrestore(>pi_lock, flags);
> }
Indeed.
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Re: [patch 6/6] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
On Tue, 27 May 2014, Jason Low wrote:
On Wed, May 21, 2014 at 8:25 PM, Thomas Gleixner t...@linutronix.de wrote:
@@ -440,32 +452,41 @@ static int rt_mutex_adjust_prio_chain(st
get_task_struct(task);
raw_spin_lock_irqsave(task-pi_lock, flags);
- if (waiter == rt_mutex_top_waiter(lock)) {
- /*
-* The waiter became the top waiter on the
-* lock. Remove the previous top waiter from the tasks
-* pi waiters list and add waiter to it.
-*/
- rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
- rt_mutex_enqueue_pi(task, waiter);
- __rt_mutex_adjust_prio(task);
-
- } else if (prerequeue_top_waiter == waiter) {
- /*
-* The waiter was the top waiter on the lock. Remove
-* waiter from the tasks pi waiters list and add the
-* new top waiter to it.
-*/
- rt_mutex_dequeue_pi(task, waiter);
- waiter = rt_mutex_top_waiter(lock);
- rt_mutex_enqueue_pi(task, waiter);
- __rt_mutex_adjust_prio(task);
-
- } else {
- /*
-* Nothing changed. No need to do any priority
-* adjustment.
-*/
+ /*
+* In case we are just following the lock chain for deadlock
+* detection we can avoid the whole requeue and priority
+* adjustment business.
+*/
+ if (requeue) {
+ if (waiter == rt_mutex_top_waiter(lock)) {
+ /*
+* The waiter became the top waiter on the
+* lock. Remove the previous top waiter from
+* the tasks pi waiters list and add waiter to
+* it.
+*/
+ rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
+ rt_mutex_enqueue_pi(task, waiter);
+ __rt_mutex_adjust_prio(task);
+
+ } else if (prerequeue_top_waiter == waiter) {
+ /*
+* The waiter was the top waiter on the
+* lock. Remove waiter from the tasks pi
+* waiters list and add the new top waiter to
+* it.
+*/
+ rt_mutex_dequeue_pi(task, waiter);
+ waiter = rt_mutex_top_waiter(lock);
+ rt_mutex_enqueue_pi(task, waiter);
+ __rt_mutex_adjust_prio(task);
+
+ } else {
+ /*
+* Nothing changed. No need to do any priority
+* adjustment.
+*/
+ }
}
raw_spin_unlock_irqrestore(task-pi_lock, flags);
In the above case, could we go 1 step further and avoid taking the pi
lock as well?
if (requeue) {
raw_spin_lock_irqsave(task-pi_lock, flags);
if (waiter == rt_mutex_top_waiter(lock)) {
/*
* The waiter became the top waiter on the
* lock. Remove the previous top waiter from
* the tasks pi waiters list and add waiter to
* it.
*/
rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
rt_mutex_enqueue_pi(task, waiter);
__rt_mutex_adjust_prio(task);
} else if (prerequeue_top_waiter == waiter) {
/*
* The waiter was the top waiter on the
* lock. Remove waiter from the tasks pi
* waiters list and add the new top waiter to
* it.
*/
rt_mutex_dequeue_pi(task, waiter);
waiter = rt_mutex_top_waiter(lock);
rt_mutex_enqueue_pi(task, waiter);
__rt_mutex_adjust_prio(task);
} else {
/*
* Nothing changed. No need to do any priority
* adjustment.
*/
}
raw_spin_unlock_irqrestore(task-pi_lock, flags);
}
Indeed.
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Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 6/6] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
On Wed, May 21, 2014 at 8:25 PM, Thomas Gleixner wrote:
> @@ -440,32 +452,41 @@ static int rt_mutex_adjust_prio_chain(st
> get_task_struct(task);
> raw_spin_lock_irqsave(>pi_lock, flags);
>
> - if (waiter == rt_mutex_top_waiter(lock)) {
> - /*
> -* The waiter became the top waiter on the
> -* lock. Remove the previous top waiter from the tasks
> -* pi waiters list and add waiter to it.
> -*/
> - rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
> - rt_mutex_enqueue_pi(task, waiter);
> - __rt_mutex_adjust_prio(task);
> -
> - } else if (prerequeue_top_waiter == waiter) {
> - /*
> -* The waiter was the top waiter on the lock. Remove
> -* waiter from the tasks pi waiters list and add the
> -* new top waiter to it.
> -*/
> - rt_mutex_dequeue_pi(task, waiter);
> - waiter = rt_mutex_top_waiter(lock);
> - rt_mutex_enqueue_pi(task, waiter);
> - __rt_mutex_adjust_prio(task);
> -
> - } else {
> - /*
> -* Nothing changed. No need to do any priority
> -* adjustment.
> -*/
> + /*
> +* In case we are just following the lock chain for deadlock
> +* detection we can avoid the whole requeue and priority
> +* adjustment business.
> +*/
> + if (requeue) {
> + if (waiter == rt_mutex_top_waiter(lock)) {
> + /*
> +* The waiter became the top waiter on the
> +* lock. Remove the previous top waiter from
> +* the tasks pi waiters list and add waiter to
> +* it.
> +*/
> + rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
> + rt_mutex_enqueue_pi(task, waiter);
> + __rt_mutex_adjust_prio(task);
> +
> + } else if (prerequeue_top_waiter == waiter) {
> + /*
> +* The waiter was the top waiter on the
> +* lock. Remove waiter from the tasks pi
> +* waiters list and add the new top waiter to
> +* it.
> +*/
> + rt_mutex_dequeue_pi(task, waiter);
> + waiter = rt_mutex_top_waiter(lock);
> + rt_mutex_enqueue_pi(task, waiter);
> + __rt_mutex_adjust_prio(task);
> +
> + } else {
> + /*
> +* Nothing changed. No need to do any priority
> +* adjustment.
> +*/
> + }
> }
>
> raw_spin_unlock_irqrestore(>pi_lock, flags);
In the above case, could we go 1 step further and avoid taking the pi
lock as well?
if (requeue) {
raw_spin_lock_irqsave(>pi_lock, flags);
if (waiter == rt_mutex_top_waiter(lock)) {
/*
* The waiter became the top waiter on the
* lock. Remove the previous top waiter from
* the tasks pi waiters list and add waiter to
* it.
*/
rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
rt_mutex_enqueue_pi(task, waiter);
__rt_mutex_adjust_prio(task);
} else if (prerequeue_top_waiter == waiter) {
/*
* The waiter was the top waiter on the
* lock. Remove waiter from the tasks pi
* waiters list and add the new top waiter to
* it.
*/
rt_mutex_dequeue_pi(task, waiter);
waiter = rt_mutex_top_waiter(lock);
rt_mutex_enqueue_pi(task, waiter);
__rt_mutex_adjust_prio(task);
} else {
/*
* Nothing changed. No need to do any priority
* adjustment.
*/
}
raw_spin_unlock_irqrestore(>pi_lock, flags);
}
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Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 6/6] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
On Wed, May 21, 2014 at 8:25 PM, Thomas Gleixner t...@linutronix.de wrote:
@@ -440,32 +452,41 @@ static int rt_mutex_adjust_prio_chain(st
get_task_struct(task);
raw_spin_lock_irqsave(task-pi_lock, flags);
- if (waiter == rt_mutex_top_waiter(lock)) {
- /*
-* The waiter became the top waiter on the
-* lock. Remove the previous top waiter from the tasks
-* pi waiters list and add waiter to it.
-*/
- rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
- rt_mutex_enqueue_pi(task, waiter);
- __rt_mutex_adjust_prio(task);
-
- } else if (prerequeue_top_waiter == waiter) {
- /*
-* The waiter was the top waiter on the lock. Remove
-* waiter from the tasks pi waiters list and add the
-* new top waiter to it.
-*/
- rt_mutex_dequeue_pi(task, waiter);
- waiter = rt_mutex_top_waiter(lock);
- rt_mutex_enqueue_pi(task, waiter);
- __rt_mutex_adjust_prio(task);
-
- } else {
- /*
-* Nothing changed. No need to do any priority
-* adjustment.
-*/
+ /*
+* In case we are just following the lock chain for deadlock
+* detection we can avoid the whole requeue and priority
+* adjustment business.
+*/
+ if (requeue) {
+ if (waiter == rt_mutex_top_waiter(lock)) {
+ /*
+* The waiter became the top waiter on the
+* lock. Remove the previous top waiter from
+* the tasks pi waiters list and add waiter to
+* it.
+*/
+ rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
+ rt_mutex_enqueue_pi(task, waiter);
+ __rt_mutex_adjust_prio(task);
+
+ } else if (prerequeue_top_waiter == waiter) {
+ /*
+* The waiter was the top waiter on the
+* lock. Remove waiter from the tasks pi
+* waiters list and add the new top waiter to
+* it.
+*/
+ rt_mutex_dequeue_pi(task, waiter);
+ waiter = rt_mutex_top_waiter(lock);
+ rt_mutex_enqueue_pi(task, waiter);
+ __rt_mutex_adjust_prio(task);
+
+ } else {
+ /*
+* Nothing changed. No need to do any priority
+* adjustment.
+*/
+ }
}
raw_spin_unlock_irqrestore(task-pi_lock, flags);
In the above case, could we go 1 step further and avoid taking the pi
lock as well?
if (requeue) {
raw_spin_lock_irqsave(task-pi_lock, flags);
if (waiter == rt_mutex_top_waiter(lock)) {
/*
* The waiter became the top waiter on the
* lock. Remove the previous top waiter from
* the tasks pi waiters list and add waiter to
* it.
*/
rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
rt_mutex_enqueue_pi(task, waiter);
__rt_mutex_adjust_prio(task);
} else if (prerequeue_top_waiter == waiter) {
/*
* The waiter was the top waiter on the
* lock. Remove waiter from the tasks pi
* waiters list and add the new top waiter to
* it.
*/
rt_mutex_dequeue_pi(task, waiter);
waiter = rt_mutex_top_waiter(lock);
rt_mutex_enqueue_pi(task, waiter);
__rt_mutex_adjust_prio(task);
} else {
/*
* Nothing changed. No need to do any priority
* adjustment.
*/
}
raw_spin_unlock_irqrestore(task-pi_lock, flags);
}
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More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
