linux-kernel - 答复: [PATCH][v2] watchdog/hardlockup: reassign last

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Message-ID: <076b0c0a3e284e5e8821fc6db161f857@baidu.com>
Date:   Tue, 22 Oct 2019 10:43:40 +0000
From:   "Li,Rongqing" <lirongqing@...du.com>
To:     "Li,Rongqing" <lirongqing@...du.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "sergey.senozhatsky.work@...il.com" 
        <sergey.senozhatsky.work@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Kan.liang@...el.com" <Kan.liang@...el.com>
Subject: 答复: [PATCH][v2] watchdog/hardlockup: reassign last_timestamp when enable nmi event

Ping

Thanks

-Li

> -----邮件原件-----
> 发件人: linux-kernel-owner@...r.kernel.org
> [mailto:linux-kernel-owner@...r.kernel.org] 代表 Li RongQing
> 发送时间: 2019年10月15日 14:34
> 收件人: akpm@...ux-foundation.org; sergey.senozhatsky.work@...il.com;
> linux-kernel@...r.kernel.org; tglx@...utronix.de; Kan.liang@...el.com
> 主题: [PATCH][v2] watchdog/hardlockup: reassign last_timestamp when
> enable nmi event
> 
> last_timestamp is not initialized and is zero after boot, or stop to forward when
> nmi watchdog is disabled; and false positives still is possible when restart NMI
> timer after stopping 120 seconds
> 
> so reassign last_timestamp always when enable nmi event
> 
> Fixes: 7edaeb6841df ("kernel/watchdog: Prevent false positives with turbo
> modes")
> Signed-off-by: Li RongQing <lirongqing@...du.com>
> Signed-off-by: Zhang Yu <zhangyu31@...du.com>
> ---
> 
> v1-->v2: make it be able to be compiled on no
> v1-->CONFIG_HARDLOCKUP_CHECK_TIMESTAMP platform
> 
> kernel/watchdog_hld.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c index
> 247bf0b1582c..f14d18280387 100644
> --- a/kernel/watchdog_hld.c
> +++ b/kernel/watchdog_hld.c
> @@ -91,11 +91,24 @@ static bool watchdog_check_timestamp(void)
>  	__this_cpu_write(last_timestamp, now);
>  	return true;
>  }
> +
> +static void watchdog_touch_timestamp(int cpu) {
> +
> +	ktime_t now = ktime_get_mono_fast_ns();
> +
> +	per_cpu(last_timestamp, cpu) = now;
> +}
>  #else
>  static inline bool watchdog_check_timestamp(void)  {
>  	return true;
>  }
> +
> +static void watchdog_touch_timestamp(int cpu) {
> +
> +}
>  #endif
> 
>  static struct perf_event_attr wd_hw_attr = { @@ -196,6 +209,7 @@ void
> hardlockup_detector_perf_enable(void)
>  	if (!atomic_fetch_inc(&watchdog_cpus))
>  		pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
> 
> +	watchdog_touch_timestamp(smp_processor_id());
>  	perf_event_enable(this_cpu_read(watchdog_ev));
>  }
> 
> @@ -274,8 +288,10 @@ void __init hardlockup_detector_perf_restart(void)
>  	for_each_online_cpu(cpu) {
>  		struct perf_event *event = per_cpu(watchdog_ev, cpu);
> 
> -		if (event)
> +		if (event) {
> +			watchdog_touch_timestamp(cpu);
>  			perf_event_enable(event);
> +		}
>  	}
>  }
> 
> --
> 2.16.2