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

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Date:	Wed, 11 Feb 2015 05:47:06 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	John Stultz <john.stultz@...aro.org>
CC:	lkml <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Miroslav Lichvar <mlichvar@...hat.com>
Subject: Re: [PATCH] time, ntp: Do not update time_state in middle of leap
 second



On 02/10/2015 06:47 PM, John Stultz wrote:
> On Sun, Feb 8, 2015 at 2:29 AM, Prarit Bhargava <prarit@...hat.com> wrote:
>> During leap second insertion testing it was noticed that a small window
>> exists where the time_state could be reset such that
>> time_state = TIME_OK, which then causes the leap second to not occur, or
>> causes the entire leap second state machine to fail.
> 
> 
> I think this description is fairly opaque, and probably needs the
> specific example of the state change transitions that motivates this
> patch.
> 
>> 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.
> 
> In this case it was a test-case bug where uninitialized data being
> passed to adjtimex (when the test intended to only read the time
> state) was causing an unexpected state change transition. So its not
> immediately obvious that resetting the state machine when the root
> called adjtimex is invalid, so it would be good to make this more
> clear and explicit (ie: show the expected state transitions and the
> command that caused the strange transition you saw).
> 
> Sorry for the slow response here, I've been on the fence as to if this
> is the right thing or not, and have needed to get some time to stare
> at this a bit more to see if I can convince myself its the right
> thing, so improving the commit message might make it more obvious to
> me and others. :)

Will do :)  I'll write up a proper and detailed description.  My bad.

P.

> 
> thanks
> -john
> 
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