Commit aef30c8d authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Thomas Gleixner
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genirq: Warn about using IRQF_ONESHOT without a threaded handler 



IRQF_ONESHOT disables the interrupt source until after the threaded
handler completed its work. This is needed to allow the threaded handler
to run - otherwise the CPU will get back to the interrupt handler
because the interrupt source remains active and the threaded handler
will not able to do its work.

Specifying IRQF_ONESHOT without a threaded handler does not make sense.
It could be a leftover if the handler _was_ threaded and changed back to
primary and the flag was not removed. This can be problematic in the
`threadirqs' case because the handler is exempt from forced-threading.
This in turn can become a problem on a PREEMPT_RT system if the handler
attempts to acquire sleeping locks.

Warn about missing threaded handlers with the IRQF_ONESHOT flag.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@kernel.org>
Reviewed-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patch.msgid.link/20260112134013.eQWyReHR@linutronix.de
parent 90876d9b

kernel/irq/manage.c

+7 −0
Original line number Diff line number Diff line
@@ -1473,6 +1473,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new) 
	if (!(new->flags & IRQF_TRIGGER_MASK))

		new->flags |= irqd_get_trigger_type(&desc->irq_data);



	/*

	 * IRQF_ONESHOT means the interrupt source in the IRQ chip will be

	 * masked until the threaded handled is done. If there is no thread

	 * handler then it makes no sense to have IRQF_ONESHOT.

	 */

	WARN_ON_ONCE(new->flags & IRQF_ONESHOT && !new->thread_fn);



	/*

	 * Check whether the interrupt nests into another interrupt

	 * thread.