linux-kernel - Re: [RFC PATCH 16/22 -v2] add get_monotonic

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]

Message-ID: <18318.51622.37470.246611@cargo.ozlabs.ibm.com>
Date:	Thu, 17 Jan 2008 14:21:10 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
Cc:	john stultz <johnstul@...ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Hellwig <hch@...radead.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tim Bird <tim.bird@...sony.com>,
	Sam Ravnborg <sam@...nborg.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Daniel Walker <dwalker@...sta.com>
Subject: Re: [RFC PATCH 16/22 -v2] add get_monotonic_cycles

Mathieu Desnoyers writes:

> Sorry for self-reply, but I thought, in the past, of a way to make this
> possible.
> 
> It would imply the creation of a new vsyscall : vgetschedperiod
> 
> It would read a counter that would increment each time the thread is
> scheduled out (or in). It would be a per thread counter

It's very hard to do a per-thread counter in the VDSO, since threads
in the same process see the same memory, by definition.  You'd have to
have an array of counters and have some way for each thread to know
which entry to read.  Also you'd have to find space for tens or
hundreds of thousands of counters, since there can be that many
threads in a process sometimes.

Paul.
--
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/