Re: [PATCH] hrtimer: CPU and entry_time is added to a warning message in hrtimer_interrupt()

From: Rei Yamamoto
Date: Fri Sep 09 2022 - 01:47:48 EST


Hi, Thomas Gleixner.

On Fri, 24 Jun 2022 16:00:11, Rei Yamamoto wrote:
> A warning message in hrtimer_interrupt() is output up to 5 times
> by default, and CPU and entry_time are also shown.
> These changes are helpful that the function spending a lot of time is clear
> by using ftrace:
> -----
> dmesg
> :
> [ 1462.836971] start repro_hrtimer_interrupt
> [ 1462.836976] test_handler = test_handler [repro] 0xffff9788f7bb3048
> :
> [ 1462.879117] hrtimer: CPU 7, entry_time = 1462807264840, interrupt took
> 60048886 ns ^^^^^ ^^^^^^^^^^^^^
>
> cat /sys/kernel/debug/tracing/trace
> :
> <idle>-0 [007] d.h1. 1462.838075: hrtimer_expire_entry:
> ^^^^^
> hrtimer=0000000041fcee42 function=test_handler [repro] now=1462807264840
> ^^^^^^^^^^^^^
> -----
>
> Signed-off-by: Rei Yamamoto <yamamoto.rei@xxxxxxxxxxxxxx>
> ---
> include/linux/hrtimer.h | 1 +
> kernel/sysctl.c | 10 ++++++++++
> kernel/time/hrtimer.c | 16 +++++++++++++++-
> 3 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
> index 0ee140176f10..1a6e03b3015b 100644
> --- a/include/linux/hrtimer.h
> +++ b/include/linux/hrtimer.h
> @@ -317,6 +317,7 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer)
> struct clock_event_device;
>
> extern void hrtimer_interrupt(struct clock_event_device *dev);
> +extern int sysctl_hrtimer_interrupt_warnings;
>
> extern unsigned int hrtimer_resolution;
>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index e52b6e372c60..b0420d60cec9 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -64,6 +64,7 @@
> #include <linux/mount.h>
> #include <linux/userfaultfd_k.h>
> #include <linux/pid.h>
> +#include <linux/hrtimer.h>
>
> #include "../lib/kstrtox.h"
>
> @@ -2038,6 +2039,15 @@ static struct ctl_table kern_table[] = {
> .extra1 = SYSCTL_ONE,
> .extra2 = SYSCTL_INT_MAX,
> },
> +#endif
> +#ifdef CONFIG_HIGH_RES_TIMERS
> + {
> + .procname = "hrtimer_interrupt_warnings",
> + .data = &sysctl_hrtimer_interrupt_warnings,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> #endif
> { }
> };
> diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
> index 0ea8702eb516..19adcbcf92e4 100644
> --- a/kernel/time/hrtimer.c
> +++ b/kernel/time/hrtimer.c
> @@ -1773,6 +1773,7 @@ static __latent_entropy void hrtimer_run_softirq(struct softirq_action *h)
> }
>
> #ifdef CONFIG_HIGH_RES_TIMERS
> +int sysctl_hrtimer_interrupt_warnings = 5;
>
> /*
> * High resolution timer interrupt
> @@ -1866,7 +1867,20 @@ void hrtimer_interrupt(struct clock_event_device *dev)
> else
> expires_next = ktime_add(now, delta);
> tick_program_event(expires_next, 1);
> - pr_warn_once("hrtimer: interrupt took %llu ns\n", ktime_to_ns(delta));
> +
> + /*
> + * If a message is output many times, the delayed funciton
> + * may be identified by resetting sysctl_hrtimer_interrupt_warnings
> + * and enabling ftrace.
> + */
> + if (sysctl_hrtimer_interrupt_warnings) {
> + if (sysctl_hrtimer_interrupt_warnings > 0)
> + sysctl_hrtimer_interrupt_warnings--;
> + pr_warn("hrtimer: CPU %d, entry_time = %llu, "
> + "interrupt took %llu ns\n",
> + cpu_base->cpu, entry_time,
> + ktime_to_ns(delta));
> + }
> }
>
> /* called with interrupts disabled */

Could you pick this patch up?

Thanks,
Rei