linux-kernel - Re: [PATCH/RFC 1/2] jump label: make enable/disable o(1)

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: <20101216205043.GB18095@Krystal>
Date:	Thu, 16 Dec 2010 15:50:43 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Jason Baron <jbaron@...hat.com>, hpa@...or.com,
	rostedt@...dmis.org, mingo@...e.hu, tglx@...utronix.de,
	andi@...stfloor.org, roland@...hat.com, rth@...hat.com,
	masami.hiramatsu.pt@...achi.com, fweisbec@...il.com,
	avi@...hat.com, davem@...emloft.net, sam@...nborg.org,
	ddaney@...iumnetworks.com, michael@...erman.id.au,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC 1/2] jump label: make enable/disable o(1)

* Peter Zijlstra (peterz@...radead.org) wrote:
> On Thu, 2010-12-16 at 15:36 -0500, Mathieu Desnoyers wrote:
> > Tracepoints keep their own reference counts for enable/disable, so a
> > simple "enable/disable" is fine as far as tracepoints are concerned. Why
> > does perf need that refcounting done by the static jumps ?
> 
> Because the refcount is all we have... Why not replace that tracepoint
> refcount with the jumplabel thing?

The reason why tracepoints need to keep their own refcount is because
they support dynamically loadable modules, and hence the refcount must
be kept outside of the modules, in a table internal to tracepoints,
so we can attach a probe to a yet unloaded module. Therefore, relying on
this lower level jump label to keep the refcount is not appropriate for
tracepoints, because the refcount only exists when the module is live.

I know that your point of view is "let users of modules suffer", but
this represents a very large portion of Linux users I am not willing to
let suffer knowingly.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
--
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/