On 22/07/2025 10:21, Jiri Slaby wrote: > > On 14. 07. 25, 10:41, Wladislav Wiebe wrote: >> This patch adds a mechanism to detect and warn about long-running IRQ >> handlers exceeding a user-defined duration threshold in microseconds. >> >> The feature is enabled via the kernel boot parameter: >> "irqhandler.duration_warn_us=<threshold_in_us>" >> >> For example, passing irqhandler.duration_warn_us=1000 will warn if an >> IRQ handler takes more than 1000 microseconds. >> >> Implementation uses local_clock() to measure the execution duration of >> IRQ handlers. When the threshold is exceeded, a ratelimited warning is >> printed: >> >> "[CPU14] long duration on IRQ[159:bad_irq_handler [long_irq]], took: 1330 us" >> >> Signed-off-by: Wladislav Wiebe <wladislav.wiebe@xxxxxxxxx> >> --- >> V1 -> V2: refactor to use local_clock() instead of jiffies and replace >> Kconfig knobs by a new command-line parameter. >> V1 link: https://lore.kernel.org/lkml/20250630124721.18232-1-wladislav.wiebe@xxxxxxxxx/ >> --- >> .../admin-guide/kernel-parameters.txt | 5 ++ >> kernel/irq/handle.c | 48 ++++++++++++++++++- >> 2 files changed, 52 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index f1f2c0874da9..fa89f21ea1e6 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -2543,6 +2543,11 @@ >> for it. Intended to get systems with badly broken >> firmware running. >> >> + irqhandler.duration_warn_us= [KNL,EARLY] >> + 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 >> diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c >> index 9489f93b3db3..eab8fdfab8d8 100644 >> --- a/kernel/irq/handle.c >> +++ b/kernel/irq/handle.c >> @@ -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_us __ro_after_init; >> + >> +static int __init irqhandler_duration_check_setup(char *arg) >> +{ >> + unsigned long val; >> + int ret; >> + >> + if (!arg) >> + return 0; >> + >> + ret = kstrtoul(arg, 0, &val); >> + if (ret) >> + return ret; >> + >> + if (val > 0) { >> + irqhandler_duration_threshold_us = val; >> + static_branch_enable(&irqhandler_duration_check_enabled); >> + } else { >> + pr_err("Invalid irqhandler.duration_warn_us setting (%lu)\n", val); >> + return -EINVAL; > > Perhaps invert the condition and drop the "else {}"? > >> + } >> + >> + return 0; >> +} >> +early_param("irqhandler.duration_warn_us", irqhandler_duration_check_setup); >> + >> +static inline void irqhandler_duration_check(u64 ts_start, unsigned int irq, >> + struct irqaction *action) > > Can be const. > >> +{ >> + u64 delta_us = (local_clock() - ts_start) >> 10; >> + >> + if (unlikely(delta_us > irqhandler_duration_threshold_us)) { >> + pr_warn_ratelimited("[CPU%d] long duration on IRQ[%u:%ps], took: %llu us\n", > > s/%d/%u/. > Do you mean "of IRQ[...]"? > >> + smp_processor_id(), irq, action->handler, delta_us); >> + } >> +} >> + >> irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc) >> { >> irqreturn_t retval = IRQ_NONE; Thanks for the comments, I've addressed them in v3: https://lore.kernel.org/lkml/20250723182836.1177-1-wladislav.wiebe@xxxxxxxxx/ - W.W.
