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From: Thomas Gleixner <tglx@linutronix.de>
To: John Stultz <john.stultz@linaro.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Kentaro Takeda <takedakn@nttdata.co.jp>,
	linux-security-module@vger.kernel.org
Subject: Re: [patch 13/13] tomoyo: Use sensible time interface
Date: Thu, 12 Jun 2014 02:22:33 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.10.1406120216480.5170@nanos> (raw)
In-Reply-To: <CALAqxLUtmY3JeHeq_RXz-Sc_jjyJQv=VRUr6bXtAge1+6bEXDA@mail.gmail.com>

On Wed, 11 Jun 2014, John Stultz wrote:

> On Wed, Jun 11, 2014 at 4:59 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > There is no point in calling gettimeofday if only the seconds part of
> > the timespec is used. Use get_seconds() instead. It's not only the
> > proper interface it's also faster.
> 
> My only caution here is you only get tick-granular time here. So if
> the second rolled over after the last tick, you'd get the previous
> second when you call get_seconds(). This can cause some surprising
> effects if the get_seconds() return value is mixed with clocksource
> granular gettimeofday() calls.

If the whole thing only cares about the seconds value, then where is
the problem?

Even if you call gettimeofday() then you still can observe this

gettimeofday(ts)
	ts.tv_sec = 99
	ts.tv_nsec = 999999999

So if you readout the related value ONE nanosecond later, then this
value will have
	ts.tv_sec = 100
	ts.tv_nsec = 0

So what's the point? The tomoyo code chose to take seconds granular
time stamps for whatever reasons. So it should be able to deal with
that, right?

Thanks,

	tglx



  reply	other threads:[~2014-06-12  0:22 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-11 23:59 [patch 00/13] time: Tree wide cleanup of interfaces and crap Thomas Gleixner
2014-06-11 23:59 ` [patch 01/13] acct: Use ktime_get_ts() Thomas Gleixner
2014-06-21 20:36   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2014-06-11 23:59 ` [patch 02/13] tsacct: " Thomas Gleixner
2014-06-21 20:37   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2014-06-11 23:59 ` [patch 03/13] delayacct: " Thomas Gleixner
2014-06-21 20:36   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2014-06-11 23:59 ` [patch 05/13] sound: " Thomas Gleixner
2014-06-12 10:42   ` Takashi Iwai
2014-06-12 10:51     ` Thomas Gleixner
2014-06-12 10:59       ` Takashi Iwai
2014-06-11 23:59 ` [patch 04/13] net: mac80211: " Thomas Gleixner
2014-06-11 23:59   ` Thomas Gleixner
2014-06-12  6:53   ` Johannes Berg
2014-06-12  9:03     ` Luis R. Rodriguez
2014-06-12  9:03       ` [Cocci] " Luis R. Rodriguez
2014-06-12  9:51       ` Julia.Lawall
2014-06-12  9:51         ` Julia.Lawall at lip6.fr
2014-06-12 10:49         ` Thomas Gleixner
2014-06-12 10:49           ` Thomas Gleixner
2014-06-11 23:59 ` [patch 06/13] sound: intel8x0: Use ktime and ktime_get() Thomas Gleixner
2014-06-11 23:59 ` [patch 08/13] firewire: Use ktime_get_ts() Thomas Gleixner
2014-06-12 12:35   ` Stefan Richter
2014-06-12 14:12     ` Thomas Gleixner
2014-06-21 20:37   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2014-06-11 23:59 ` [patch 07/13] kdb: " Thomas Gleixner
2014-06-21 20:37   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2014-06-11 23:59 ` [patch 10/13] time: Remove do_posix_clock_monotonic_gettime() Thomas Gleixner
2014-06-11 23:59 ` [patch 09/13] fork: Use ktime_get_ts() Thomas Gleixner
2014-06-21 20:37   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2014-06-11 23:59 ` [patch 11/13] wireless: mwifiex: Use the proper interfaces Thomas Gleixner
2014-06-11 23:59   ` Thomas Gleixner
2014-06-12  3:22   ` Bing Zhao
2014-06-12  8:31     ` [patch V2] " Thomas Gleixner
2014-06-12  8:38       ` Johannes Berg
2014-06-13 18:28         ` Bing Zhao
2014-06-13 18:28           ` Bing Zhao
2014-06-11 23:59 ` [patch 12/13] net: mac80211: Remove silly timespec dance Thomas Gleixner
2014-06-11 23:59   ` Thomas Gleixner
2014-06-12  6:49   ` Johannes Berg
2014-06-12  8:19     ` Thomas Gleixner
2014-06-12  8:35       ` net_timedelta() affected by settimeofday() (was: [patch 12/13] net: mac80211: Remove silly timespec dance) Johannes Berg
2014-06-12  8:39         ` Johannes Berg
2014-06-12  8:57           ` Thomas Gleixner
2014-06-12  9:21             ` Johannes Berg
2014-06-12 14:09               ` Thomas Gleixner
2014-06-12 14:09                 ` Thomas Gleixner
2014-06-13 17:58                 ` Johannes Berg
2014-06-11 23:59 ` [patch 13/13] tomoyo: Use sensible time interface Thomas Gleixner
2014-06-12  0:08   ` John Stultz
2014-06-12  0:22     ` Thomas Gleixner [this message]
2014-06-12  0:28       ` John Stultz
2014-06-12  0:36         ` Thomas Gleixner
2014-06-12 11:53   ` Tetsuo Handa
2014-06-21 20:37   ` [tip:timers/core] " tip-bot for Thomas Gleixner

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