linux-kernel - Re: [PATCH v3 3/4] ftrace: add tracepoint for hrtimer

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

Date:	Thu, 23 Jul 2009 18:01:14 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Zhaolei <zhaolei@...fujitsu.com>, kosaki.motohiro@...fujitsu.com,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Anton Blanchard <anton@...ba.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] ftrace: add tracepoint for hrtimer



Peter Zijlstra wrote:

> OK, so what you want to measure is the time of the actual callback
> happening (hrtimer_entry) vs that where you would have expected it to
> happen (hrtimer_start + delay), right?
> 

Yes

> So what's wrong with printing the expected expiration time in the
> hrtimer_start tracepoint in the cheap clock units?
> 

Is "cheap clock units" means jiffies time?

If so, we need to convert "expire time" into jiffies time, but
I searched ways for this type of converting but found nothing.

I'm afraid it's hard to do as below example:
  insmod-3821  [001]  3192.239335: hrtimer_start: timer=d08a1480  expires=1245162841000000000 ns
  <idle>-0     [001]  3201.506127: hrtimer_expire: timer=d08a1480

We can't convert 1245162841000000000ns to jiffies if we don't know
the xtime/wall_to_monotonic at hrimter_start.
And the expire time that got by _start() maybe wrong because user
can change time of day between hrtimer_start() and hrtimer_expire().

What your opinion?

> 
> 
> 
--
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/