Commit 673f1244 authored by Wladislav Wiebe's avatar Wladislav Wiebe Committed by Thomas Gleixner
Browse files

genirq: Add support for warning on long-running interrupt handlers 



Introduce a mechanism to detect and warn about prolonged interrupt handlers.
With a new command-line parameter (irqhandler.duration_warn_us=), users can
configure the duration threshold in microseconds when a warning in such
format should be emitted:

"[CPU14] long duration of IRQ[159:bad_irq_handler [long_irq]], took: 1330 us"

The implementation uses local_clock() to measure the execution duration of the
generic IRQ per-CPU event handler.

Signed-off-by: default avatarWladislav Wiebe <wladislav.wiebe@nokia.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarJiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/all/20250804093525.851-1-wladislav.wiebe@nokia.com
parent 55b48e23

Documentation/admin-guide/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -2606,6 +2606,11 @@ 
			for it. Intended to get systems with badly broken

			firmware running.



	irqhandler.duration_warn_us= [KNL]

			Warn if an IRQ handler exceeds the specified duration

			threshold in microseconds. Useful for identifying

			long-running IRQs in the system.



	irqpoll		[HW]

			When an interrupt is not handled search all handlers

			for it. Also check all handlers each timer

kernel/irq/handle.c

+48 −1
Original line number Diff line number Diff line
@@ -136,6 +136,44 @@ void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action) 
	wake_up_process(action->thread);

}



static DEFINE_STATIC_KEY_FALSE(irqhandler_duration_check_enabled);

static u64 irqhandler_duration_threshold_ns __ro_after_init;



static int __init irqhandler_duration_check_setup(char *arg)

{

	unsigned long val;

	int ret;



	ret = kstrtoul(arg, 0, &val);

	if (ret) {

		pr_err("Unable to parse irqhandler.duration_warn_us setting: ret=%d\n", ret);

		return 0;

	}



	if (!val) {

		pr_err("Invalid irqhandler.duration_warn_us setting, must be > 0\n");

		return 0;

	}



	irqhandler_duration_threshold_ns = val * 1000;

	static_branch_enable(&irqhandler_duration_check_enabled);



	return 1;

}

__setup("irqhandler.duration_warn_us=", irqhandler_duration_check_setup);



static inline void irqhandler_duration_check(u64 ts_start, unsigned int irq,

					     const struct irqaction *action)

{

	u64 delta_ns = local_clock() - ts_start;



	if (unlikely(delta_ns > irqhandler_duration_threshold_ns)) {

		pr_warn_ratelimited("[CPU%u] long duration of IRQ[%u:%ps], took: %llu us\n",

				    smp_processor_id(), irq, action->handler,

				    div_u64(delta_ns, NSEC_PER_USEC));

	}

}



irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc)

{

	irqreturn_t retval = IRQ_NONE;
@@ -155,7 +193,16 @@ irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc) 
			lockdep_hardirq_threaded();



		trace_irq_handler_entry(irq, action);



		if (static_branch_unlikely(&irqhandler_duration_check_enabled)) {

			u64 ts_start = local_clock();



			res = action->handler(irq, action->dev_id);

			irqhandler_duration_check(ts_start, irq, action);

		} else {

			res = action->handler(irq, action->dev_id);

		}



		trace_irq_handler_exit(irq, action, res);



		if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pS enabled interrupts\n",