From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Clark Williams <williams@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jon Masters <jcm@redhat.com>, Daniel Wagner <wagi@monom.org>,
Carsten Emde <C.Emde@osadl.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCH v2 0/4] tracing: Add Hardware Latency detector tracer
Date: Fri, 19 Aug 2016 17:05:51 +0200 [thread overview]
Message-ID: <20160819150551.GE10153@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160819102620.763bd7a0@gandalf.local.home>
On Fri, Aug 19, 2016 at 10:26:20AM -0400, Steven Rostedt wrote:
> > In any case, for those you could probably use ktime_get_mono_fast_ns().
>
> Is that safe to call from NMI?
It should be, we were very careful to make it so. Also read the comment
with __ktime_get_fast_ns().
> Looking into the code I see:
>
> now = ktime_to_ns(tkr->base) + timekeeping_get_ns(tkr);
>
> where timekeeping_get_ns() has:
>
> timekeeping_get_delta()
>
> which does:
>
> read_seqcount_begin()
>
> which has (eventually):
That's a bug in CONFIG_DEBUG_TIMEKEEPING, if you look at the
!timekeeping_get_delta() it does no such thing.
John, looks like 4ca22c2648f9 ("timekeeping: Add warnings when overflows
or underflows are observed") buggered things.
next prev parent reply other threads:[~2016-08-19 15:06 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-10 13:53 [PATCH v2 0/4] tracing: Add Hardware Latency detector tracer Steven Rostedt
2016-08-10 13:53 ` [PATCH v2 1/4] tracing: Added hardware latency tracer Steven Rostedt
2016-08-22 17:27 ` Nilay Vaish
2016-08-22 19:16 ` Steven Rostedt
2016-08-10 13:53 ` [PATCH v2 2/4] tracing: Add documentation for hwlat_detector tracer Steven Rostedt
2016-08-10 13:53 ` [PATCH v2 3/4] tracing: Have hwlat trace migrate across tracing_cpumask CPUs Steven Rostedt
2016-08-10 13:54 ` [PATCH v2 4/4] tracing: Add NMI tracing in hwlat detector Steven Rostedt
2016-08-12 18:13 ` [PATCH v2 0/4] tracing: Add Hardware Latency detector tracer Daniel Bristot de Oliveira
2016-08-19 14:09 ` Peter Zijlstra
2016-08-19 14:26 ` Steven Rostedt
2016-08-19 15:05 ` Peter Zijlstra [this message]
2016-08-19 16:36 ` John Stultz
2016-08-23 8:47 ` Peter Zijlstra
2016-08-23 8:48 ` Thomas Gleixner
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