linux-kernel - Re: [PATCH 2/7] timekeeping: Ignore the bogus sleep time if pm

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Message-ID: <20161129071955.GB29412@gmail.com>
Date:   Tue, 29 Nov 2016 08:19:55 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>, Chen Yu <yu.c.chen@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Xunlei Pang <xlpang@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Len Brown <lenb@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Pavel Machek <pavel@....cz>,
        Thomas Gleixner <tglx@...utronix.de>,
        Prarit Bhargava <prarit@...hat.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH 2/7] timekeeping: Ignore the bogus sleep time if pm_trace
 is enabled


* John Stultz <john.stultz@...aro.org> wrote:

> From: Chen Yu <yu.c.chen@...el.com>
> 
> Previously we encountered some memory overflow issues due to
> the bogus sleep time brought by inconsistent rtc, which is
> triggered when pm_trace is enabled, and we have fixed it
> in recent kernel. However it's improper in the first place
> to call __timekeeping_inject_sleeptime() in case that pm_trace
> is enabled simply because that "hash" time value will wreckage
> the timekeeping subsystem.

s/

 Previously we encountered memory overflow issues due to
 bogus sleep time brought by an inconsistent RTC, which is
 triggered when pm_trace is enabled, and we have fixed it
 in recent kernels. However it's improper in the first place
 to call __timekeeping_inject_sleeptime() in case pm_trace
 is enabled simply because the "hash" time value will wreckage
 the timekeeping subsystem.

Half a dozen typos ...

> This patch is originally written by Thomas, which would bypass
> the bogus rtc interval when pm_trace is enabled.
> Meanwhile, if system succeed to resume back with pm_trace set, the
> users are warned to adjust the bogus rtc either by 'ntpdate' or
> 'rdate', by resetting pm_trace_rtc_abused to false, otherwise above
> tools might not work as expected.

s/

 This patch was originally written by Thomas, which would bypass
 the bogus RTC interval when pm_trace is enabled.
 Meanwhile, if the system succeeds to resume back with pm_trace set,
 users are warned to adjust the bogus RTC either by 'ntpdate' or
 'rdate', by resetting pm_trace_rtc_abused to false, otherwise above
 tools might not work as expected.

> +	/*
> +	 * If pm_trace abused the RTC as storage set the timespec to 0
> +	 * which tells the caller that this RTC value is bogus.
> +	 */

s/
	/*
	 * If pm_trace abused the RTC as storage, set the timespec to 0,
	 * which tells the caller that this RTC value is bogus.
	 */

> @@ -74,6 +75,9 @@
>  
>  #define DEVSEED (7919)
>  
> +bool pm_trace_rtc_abused __read_mostly;
> +EXPORT_SYMBOL(pm_trace_rtc_abused);

EXPORT_SYMBOL_GPL()

> +static int pm_trace_notify(struct notifier_block *nb,
> +				unsigned long mode, void *_unused)

Please no nonsensical linebreaks in the middle of an argument list.

> +{
> +	switch (mode) {
> +	case PM_POST_HIBERNATION:
> +	case PM_POST_SUSPEND:
> +		if (pm_trace_rtc_abused) {
> +			pm_trace_rtc_abused = false;
> +			pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset.\n");


s/to reset./to reset it.

Thanks,

	Ingo