linux-kernel - Re: [PATCH] time, ntp: Do not update time

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Message-ID: <20150204163005.GF26460@localhost>
Date:	Wed, 4 Feb 2015 17:30:05 +0100
From:	Miroslav Lichvar <mlichvar@...hat.com>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] time, ntp: Do not update time_state in middle of leap

Prarit Bhargava wrote:
> While this is highly unlikely to ever happen in the real world it is
> still something we should protect against, as breaking the state machine
> is obviously bad.

I'm not sure what exactly breaks here. If the PLL is disabled before
time_state is set to TIME_OOP, the insertion/deletion will be aborted.
If after that, adjtimex() will return with TIME_ERROR as expected, or
not?

>  static inline void process_adj_status(struct timex *txc, struct timespec64 *ts)
>  {
> -	if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
> +	if ((time_status & STA_PLL) && !(txc->status & STA_PLL) &&
> +	    (time_state != TIME_OOP)) {
>  		time_state = TIME_OK;
>  		time_status = STA_UNSYNC;
>  		/* restart PPS frequency calibration */

Shouldn't be time_status reset and the PPS calibration restarted even
when state is TIME_OOP?

-- 
Miroslav Lichvar
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