From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Clemens Ladisch <clemens@ladisch.de>,
Sultan Alsawaf <sultan@kerneltoast.com>,
Waiman Long <longman@redhat.com>, X86 ML <x86@kernel.org>
Subject: Re: infinite loop in read_hpet from ktime_get_boot_fast_ns
Date: Thu, 13 Jun 2019 17:18:50 +0200 [thread overview]
Message-ID: <CAHmME9pOWk_ZteUZc_PT19rMn1kfYcXtmLcyAy5sncdV1tNuiQ@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a15NTV=njOjz-ccYL8=_q_MdEru0A+jeE=f7ufUTOOTgw@mail.gmail.com>
Hey Arnd, Peter,
On Wed, Jun 12, 2019 at 4:01 PM Arnd Bergmann <arnd@arndb.de> wrote:
> Documentation/core-api/timekeeping.rst describes the timekeeping
> interfaces. I think what you want here is ktime_get_coarse_boottime().
>
> Note that "coarse" means "don't access the hardware clocksource"
> here, which is faster than "fast", but less accurate.
>
> This is updated as often as "jiffies_64", but is in nanosecond resolution
> and takes suspended time into account.
Oh, thanks. Indeed ktime_get_coarse_boottime seems even better. It's
perhaps a bit slower, in that it has that seqlock, but that might give
better synchronization between CPUs as well.
Peter - any immediate downside you can think of compared to local_clock()?
Jason
next prev parent reply other threads:[~2019-06-13 15:19 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-07 14:14 infinite loop in read_hpet from ktime_get_boot_fast_ns Jason A. Donenfeld
2019-06-11 21:09 ` Thomas Gleixner
2019-06-11 21:40 ` Waiman Long
2019-06-12 9:02 ` Peter Zijlstra
2019-06-12 9:44 ` Jason A. Donenfeld
2019-06-12 12:28 ` Peter Zijlstra
2019-06-12 12:31 ` Peter Zijlstra
2019-06-12 12:58 ` Jason A. Donenfeld
2019-06-12 15:27 ` Peter Zijlstra
2019-06-12 19:46 ` Arnd Bergmann
2019-06-18 17:34 ` Jason A. Donenfeld
2019-06-12 14:01 ` Arnd Bergmann
2019-06-13 15:18 ` Jason A. Donenfeld [this message]
2019-06-13 15:40 ` Arnd Bergmann
2019-06-13 16:17 ` Jason A. Donenfeld
2019-06-13 16:26 ` Thomas Gleixner
2019-06-13 16:34 ` Jason A. Donenfeld
2019-06-13 16:41 ` Jason A. Donenfeld
2019-06-13 19:53 ` Thomas Gleixner
2019-06-14 9:14 ` Jason A. Donenfeld
2019-06-14 9:44 ` Thomas Gleixner
2019-06-14 9:56 ` Jason A. Donenfeld
2019-06-14 9:48 ` [PATCH] timekeeping: add get_jiffies_boot_64() for jiffies including sleep Jason A. Donenfeld
2019-06-14 9:55 ` [tip:timers/urgent] timekeeping: Repair ktime_get_coarse*() granularity tip-bot for Thomas Gleixner
2019-06-14 11:18 ` Arnd Bergmann
2019-06-12 9:29 ` infinite loop in read_hpet from ktime_get_boot_fast_ns Peter Zijlstra
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