Commit 591d2fb0 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

genirq: Delegate irq affinity setting to the irq thread 



irq_set_thread_affinity() calls set_cpus_allowed_ptr() which might
sleep, but irq_set_thread_affinity() is called with desc->lock held
and can be called from hard interrupt context as well. The code has
another bug as it does not hold a ref on the task struct as required
by set_cpus_allowed_ptr().

Just set the IRQTF_AFFINITY bit in action->thread_flags. The next time
the thread runs it migrates itself. Solves all of the above problems
nicely.

Add kerneldoc to irq_set_thread_affinity() while at it.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
parent aea1f796

include/linux/interrupt.h

+2 −0
Original line number Diff line number Diff line
@@ -64,11 +64,13 @@ 
 * IRQTF_RUNTHREAD - signals that the interrupt handler thread should run

 * IRQTF_DIED      - handler thread died

 * IRQTF_WARNED    - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed

 * IRQTF_AFFINITY  - irq thread is requested to adjust affinity

 */

enum {

	IRQTF_RUNTHREAD,

	IRQTF_DIED,

	IRQTF_WARNED,

	IRQTF_AFFINITY,

};



typedef irqreturn_t (*irq_handler_t)(int, void *);

kernel/irq/internals.h

+1 −2
Original line number Diff line number Diff line
@@ -42,8 +42,7 @@ static inline void unregister_handler_proc(unsigned int irq, 


extern int irq_select_affinity_usr(unsigned int irq);



extern void

irq_set_thread_affinity(struct irq_desc *desc, const struct cpumask *cpumask);

extern void irq_set_thread_affinity(struct irq_desc *desc);



/*

 * Debugging printout:

kernel/irq/manage.c

+44 −6
Original line number Diff line number Diff line
@@ -80,14 +80,22 @@ int irq_can_set_affinity(unsigned int irq) 
	return 1;

}



void

irq_set_thread_affinity(struct irq_desc *desc, const struct cpumask *cpumask)

/**

 *	irq_set_thread_affinity - Notify irq threads to adjust affinity

 *	@desc:		irq descriptor which has affitnity changed

 *

 *	We just set IRQTF_AFFINITY and delegate the affinity setting

 *	to the interrupt thread itself. We can not call

 *	set_cpus_allowed_ptr() here as we hold desc->lock and this

 *	code can be called from hard interrupt context.

 */

void irq_set_thread_affinity(struct irq_desc *desc)

{

	struct irqaction *action = desc->action;



	while (action) {

		if (action->thread)

			set_cpus_allowed_ptr(action->thread, cpumask);

			set_bit(IRQTF_AFFINITY, &action->thread_flags);

		action = action->next;

	}

}
@@ -112,7 +120,7 @@ int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask) 
	if (desc->status & IRQ_MOVE_PCNTXT) {

		if (!desc->chip->set_affinity(irq, cpumask)) {

			cpumask_copy(desc->affinity, cpumask);

			irq_set_thread_affinity(desc, cpumask);

			irq_set_thread_affinity(desc);

		}

	}

	else {
@@ -122,7 +130,7 @@ int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask) 
#else

	if (!desc->chip->set_affinity(irq, cpumask)) {

		cpumask_copy(desc->affinity, cpumask);

		irq_set_thread_affinity(desc, cpumask);

		irq_set_thread_affinity(desc);

	}

#endif

	desc->status |= IRQ_AFFINITY_SET;
@@ -176,7 +184,7 @@ int irq_select_affinity_usr(unsigned int irq) 
	spin_lock_irqsave(&desc->lock, flags);

	ret = setup_affinity(irq, desc);

	if (!ret)

		irq_set_thread_affinity(desc, desc->affinity);

		irq_set_thread_affinity(desc);

	spin_unlock_irqrestore(&desc->lock, flags);



	return ret;
@@ -443,6 +451,34 @@ static int irq_wait_for_interrupt(struct irqaction *action) 
	return -1;

}



/*

 * Check whether we need to change the affinity of the interrupt thread.

 */

static void

irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action)

{

	cpumask_var_t mask;



	if (!test_and_clear_bit(IRQTF_AFFINITY, &action->thread_flags))

		return;



	/*

	 * In case we are out of memory we set IRQTF_AFFINITY again and

	 * try again next time

	 */

	if (!alloc_cpumask_var(&mask, GFP_KERNEL)) {

		set_bit(IRQTF_AFFINITY, &action->thread_flags);

		return;

	}



	spin_lock_irq(&desc->lock);

	cpumask_copy(mask, desc->affinity);

	spin_unlock_irq(&desc->lock);



	set_cpus_allowed_ptr(current, mask);

	free_cpumask_var(mask);

}



/*

 * Interrupt handler thread

 */
@@ -458,6 +494,8 @@ static int irq_thread(void *data) 


	while (!irq_wait_for_interrupt(action)) {



		irq_thread_check_affinity(desc, action);



		atomic_inc(&desc->threads_active);



		spin_lock_irq(&desc->lock);

kernel/irq/migration.c

+1 −1
Original line number Diff line number Diff line
@@ -45,7 +45,7 @@ void move_masked_irq(int irq) 
		   < nr_cpu_ids))

		if (!desc->chip->set_affinity(irq, desc->pending_mask)) {

			cpumask_copy(desc->affinity, desc->pending_mask);

			irq_set_thread_affinity(desc, desc->pending_mask);

			irq_set_thread_affinity(desc);

		}



	cpumask_clear(desc->pending_mask);

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