From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
LKML <linux-kernel@vger.kernel.org>,
clemens@ladisch.de, Sultan Alsawaf <sultan@kerneltoast.com>,
Waiman Long <longman@redhat.com>,
x86@kernel.org
Subject: Re: infinite loop in read_hpet from ktime_get_boot_fast_ns
Date: Wed, 12 Jun 2019 11:02:57 +0200 [thread overview]
Message-ID: <20190612090257.GF3436@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.21.1906112257120.2214@nanos.tec.linutronix.de>
On Tue, Jun 11, 2019 at 11:09:20PM +0200, Thomas Gleixner wrote:
> Jason,
>
> On Fri, 7 Jun 2019, Jason A. Donenfeld wrote:
>
> Adding a few more people on cc and keeping full context.
>
> > Hey Thomas,
> >
> > After some discussions here prior about the different clocks
> > available, WireGuard uses ktime_get_boot_fast_ns() pretty extensively.
> > The requirement is for a quasi-accurate monotonic counter that takes
> > into account sleep time, and this seems to fit the bill pretty well.
How quasi? Do the comments in kernel/sched/clock.c look like something
you could use?
As already mentioned in the other tasks, anything ktime will be
horrifically crap when it ends up using the HPET, the code in
kernel/sched/clock.c is a best effort to keep using TSC even when it is
deemed unusable for timekeeping.
next prev parent reply other threads:[~2019-06-12 9:03 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 [this message]
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
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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