From: David Ahern <daahern@cisco.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
acme@ghostprotocols.net, mingo@elte.hu, peterz@infradead.org,
fweisbec@gmail.com, paulus@samba.org
Subject: Re: [PATCH 1/5] perf events: add support for realtime clock attribute
Date: Sun, 20 Mar 2011 13:49:18 -0600 [thread overview]
Message-ID: <4D865A3E.9040605@cisco.com> (raw)
In-Reply-To: <alpine.LFD.2.00.1103202000500.2787@localhost6.localdomain6>
On 03/20/11 13:08, Thomas Gleixner wrote:
> On Sun, 20 Mar 2011, David Ahern wrote:
>> +
>> + if (sample_type & PERF_SAMPLE_REALTIME)
>> + data->realtime = ktime_to_ns(ktime_get_real());
>
> That's going to live lock on any sample which happens to hit in a
> xtime_lock write locked section. I knew why I suggested adding
> tracepoints to the timekeeping code :)
Hmmm.... Can you give an example of when perf samples could be generated
with xtime write locked? What are the rules for when ktime_get_real can
be invoked?
David
>
> Thanks,
>
> tglx
next prev parent reply other threads:[~2011-03-20 19:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-20 18:54 [PATCH 0/5] perf events: Add time-of-day to perf samples David Ahern
2011-03-20 18:54 ` [PATCH 1/5] perf events: add support for realtime clock attribute David Ahern
2011-03-20 19:08 ` Thomas Gleixner
2011-03-20 19:49 ` David Ahern [this message]
2011-03-20 20:05 ` Thomas Gleixner
2011-03-20 18:54 ` [PATCH 2/5] perf events: userspace plumbing for realtime sample attribute David Ahern
2011-03-20 18:54 ` [PATCH 3/5] perf record: add time-of-day option David Ahern
2011-03-20 18:54 ` [PATCH 4/5] perf script: add support for time-of-day strings in output David Ahern
2011-03-20 18:54 ` [PATCH 5/5] perf python: add REALTIME to constants David Ahern
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