Commit 471ba0e6 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Ingo Molnar
Browse files

irq_work: Do not raise an IPI when queueing work on the local CPU 



The QEMU PowerPC/PSeries machine model was not expecting a self-IPI,
and it may be a bit surprising thing to do, so have irq_work_queue_on
do local queueing when target is the current CPU.

Suggested-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Reported-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg@kaod.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190409093403.20994-1-npiggin@gmail.com


[ Simplified the preprocessor comments.
  Fixed unbalanced curly brackets pointed out by Thomas. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2d65c42b

kernel/irq_work.c

+42 −33
Original line number Diff line number Diff line
@@ -56,6 +56,36 @@ void __weak arch_irq_work_raise(void) 
	 */

}



/* Enqueue on current CPU, work must already be claimed and preempt disabled */

static void __irq_work_queue_local(struct irq_work *work)

{

	/* If the work is "lazy", handle it from next tick if any */

	if (work->flags & IRQ_WORK_LAZY) {

		if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&

		    tick_nohz_tick_stopped())

			arch_irq_work_raise();

	} else {

		if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))

			arch_irq_work_raise();

	}

}



/* Enqueue the irq work @work on the current CPU */

bool irq_work_queue(struct irq_work *work)

{

	/* Only queue if not already pending */

	if (!irq_work_claim(work))

		return false;



	/* Queue the entry and raise the IPI if needed. */

	preempt_disable();

	__irq_work_queue_local(work);

	preempt_enable();



	return true;

}

EXPORT_SYMBOL_GPL(irq_work_queue);



/*

 * Enqueue the irq_work @work on @cpu unless it's already pending

 * somewhere.
@@ -64,53 +94,32 @@ void __weak arch_irq_work_raise(void) 
 */

bool irq_work_queue_on(struct irq_work *work, int cpu)

{

#ifndef CONFIG_SMP

	return irq_work_queue(work);



#else /* CONFIG_SMP: */

	/* All work should have been flushed before going offline */

	WARN_ON_ONCE(cpu_is_offline(cpu));



#ifdef CONFIG_SMP



	/* Arch remote IPI send/receive backend aren't NMI safe */

	WARN_ON_ONCE(in_nmi());



	/* Only queue if not already pending */

	if (!irq_work_claim(work))

		return false;



	preempt_disable();

	if (cpu != smp_processor_id()) {

		/* Arch remote IPI send/receive backend aren't NMI safe */

		WARN_ON_ONCE(in_nmi());

		if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))

			arch_send_call_function_single_ipi(cpu);



#else /* #ifdef CONFIG_SMP */

	irq_work_queue(work);

#endif /* #else #ifdef CONFIG_SMP */



	return true;

}



/* Enqueue the irq work @work on the current CPU */

bool irq_work_queue(struct irq_work *work)

{

	/* Only queue if not already pending */

	if (!irq_work_claim(work))

		return false;



	/* Queue the entry and raise the IPI if needed. */

	preempt_disable();



	/* If the work is "lazy", handle it from next tick if any */

	if (work->flags & IRQ_WORK_LAZY) {

		if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&

		    tick_nohz_tick_stopped())

			arch_irq_work_raise();

	} else {

		if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))

			arch_irq_work_raise();

		__irq_work_queue_local(work);

	}



	preempt_enable();



	return true;

#endif /* CONFIG_SMP */

}

EXPORT_SYMBOL_GPL(irq_work_queue);





bool irq_work_needs_cpu(void)

{

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