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Message-Id: <20221107002044.95213-1-yamamoto.rei@jp.fujitsu.com>
Date: Mon, 7 Nov 2022 09:20:44 +0900
From: Rei Yamamoto <yamamoto.rei@...fujitsu.com>
To: tglx@...utronix.de
Cc: geert+renesas@...der.be, linux-kernel@...r.kernel.org,
yamamoto.rei@...fujitsu.com
Subject: Re: [PATCH] hrtimer: CPU and entry_time is added to a warning message in hrtimer_interrupt()
Hi, Thomas Gleixner.
On Fri, 9 Sep 2022 14:22:11, Rei Yamamoto wrote:
> 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@...fujitsu.com>
>> ---
>> 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?
Do you have any comments?
Thanks,
Rei
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