linux-kernel - Re: [PATCH 1/5] perf events: add support for realtime clock attribute

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Sun, 20 Mar 2011 21:05:28 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Ahern <daahern@...co.com>
cc:	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	acme@...stprotocols.net, mingo@...e.hu, peterz@...radead.org,
	fweisbec@...il.com, paulus@...ba.org
Subject: Re: [PATCH 1/5] perf events: add support for realtime clock
 attribute

On Sun, 20 Mar 2011, David Ahern wrote:

> 
> 
> 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?

NMI triggered samples can hit at any time.

Any tracepoint which we might add to the time keeping code inside the
xtime locked regions. And I don't want to see a restriction there.

> What are the rules for when ktime_get_real can be invoked?

Outside of xtime write locked regions.

Thanks,

	tglx

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/