linux-kernel - Re: [PATCH RESEND] timer stats: reset entries when disable the timer usage statistics

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 for Android: free password hash cracker in your pocket

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

Date:	Thu, 10 Oct 2013 06:35:19 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Dong Zhu <bluezhudong@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] timer stats: reset entries when disable the timer
 usage statistics


* Dong Zhu <bluezhudong@...il.com> wrote:

> From f41628c61d8a9172677ba33a55b61e37ce28f7a6 Mon Sep 17 00:00:00 2001
> From: Dong Zhu <bluezhudong@...il.com> 
> Date: Thu, 10 Oct 2013 10:38:13 +0800
> 
> When we stop timer statistics collection (via echo 0 > 
> /proc/timers_stats), the statistics data is still exported as if it were 
> correct, which can cause applicaitons to misuse the statistics.

What misuse do you mean?

> This patch resets the statistics when we stop collecting them, to avoid 
> this problem.

Well, this loses the handy 'snapshot' property of /proc/timer_stats. 
Before this change one could do:

	echo 1 > /proc/timers_stats
	sleep 60 # run system workload
	echo 0 > /proc/timers_stats

and examine the 1-minute collection result without it changing. Your 
change, if I understand it correctly, zeroes it all out.

Instead of this change I'd suggest adding a 'status' line, with two 
outputs:

	Status: collection active

	Status: collection disabled

Thanks,

	Ingo
--
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/