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From: Ingo Molnar <mingo@kernel.org>
To: John Stultz <john.stultz@linaro.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
	Dave Jones <davej@codemonkey.org.uk>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Richard Cochran <richardcochran@gmail.com>,
	Prarit Bhargava <prarit@redhat.com>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 07/12] time: Try to catch clocksource delta underflows
Date: Sat, 7 Mar 2015 10:34:35 +0100	[thread overview]
Message-ID: <20150307093435.GF30888@gmail.com> (raw)
In-Reply-To: <1425696603-16878-8-git-send-email-john.stultz@linaro.org>


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

> In the case where there is a broken clocksource
> where there are multiple actual clocks that
> aren't perfectly aligned, we may see small "negative"
> deltas when we subtract now from cycle_last.

So this is a typical example where putting argument references is 
really helpful. Consider these two variants:

   deltas when we subtract now from cycle_last.

   deltas when we subtract 'now' from 'cycle_last'.

I had to read the first variant three times until I realized that 
'now' is a C variable misleadingly inserted into English text.

> The values are actually negative with respect to the
> clocksource mask value, not necessarily negative
> if cast to a s64, but we can check by checking the
> delta see if it is a small (relative to the mask)
> negative value (again negative relative to the mask).

typo.

Thanks,

	Ingo

  reply	other threads:[~2015-03-07  9:34 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-07  2:49 [PATCH 00/12] Increased clocksource validation and cleanups (v3) John Stultz
2015-03-07  2:49 ` [PATCH 01/12] clocksource: Simplify clocks_calc_max_nsecs logic John Stultz
2015-03-07  9:20   ` Ingo Molnar
2015-03-07  2:49 ` [PATCH 02/12] clocksource: Simplify logic around clocksource wrapping saftey margins John Stultz
2015-03-07  9:22   ` Ingo Molnar
2015-03-07  2:49 ` [PATCH 03/12] clocksource: Remove clocksource_max_deferment() John Stultz
2015-03-07  9:18   ` Ingo Molnar
2015-03-07  2:49 ` [PATCH 04/12] clocksource: Add max_cycles to clocksource structure John Stultz
2015-03-07  9:54   ` Ingo Molnar
2015-03-07  2:49 ` [PATCH 05/12] time: Add debugging checks to warn if we see delays John Stultz
2015-03-07  9:22   ` Paul Bolle
2015-03-07  9:29   ` Ingo Molnar
2015-03-07  2:49 ` [PATCH 06/12] time: Add infrastructure to cap clocksource reads to the max_cycles value John Stultz
2015-03-07  9:32   ` Ingo Molnar
2015-03-07  2:49 ` [PATCH 07/12] time: Try to catch clocksource delta underflows John Stultz
2015-03-07  9:34   ` Ingo Molnar [this message]
2015-03-07  2:49 ` [PATCH 08/12] time: Add warnings when overflows or underflows are observed John Stultz
2015-03-07  9:40   ` Ingo Molnar
2015-03-09 16:50     ` John Stultz
2015-03-10  5:05       ` Ingo Molnar
2015-03-07  2:50 ` [PATCH 09/12] clocksource: Improve clocksource watchdog reporting John Stultz
2015-03-07  2:50 ` [PATCH 10/12] clocksource: Mostly kill clocksource_register() John Stultz
2015-03-07  9:45   ` Ingo Molnar
2015-03-07  2:50 ` [PATCH 11/12] sparc: Convert to using clocksource_register_hz() John Stultz
2015-03-07  9:46   ` Ingo Molnar
2015-03-07  2:50 ` [PATCH 12/12] clocksource: Add some debug info about clocksources being registered John Stultz
2015-03-07  9:50   ` Ingo Molnar
2015-03-12  3:16     ` John Stultz
  -- strict thread matches above, loose matches on Subject: below --
2015-01-23  0:09 [PATCH 00/12][RFC] Increased clocksource validation and cleanups (v2) John Stultz
2015-01-23  0:09 ` [PATCH 07/12] time: Try to catch clocksource delta underflows John Stultz

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