linux-kernel - Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu

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: <1316531987.29966.65.camel@gandalf.stny.rr.com>
Date:	Tue, 20 Sep 2011 11:19:47 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Christoph Lameter <cl@...two.org>
Cc:	Valdis.Kletnieks@...edu, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for
 this_cpu_read/write()

On Tue, 2011-09-20 at 09:57 -0500, Christoph Lameter wrote:

> this_cpu_xx functions are made for those locations that have
> preemption enabled. If you can use those function (classic case is a
> per cpu counter increment in the network subsystem) then you can avoid
> preempt disable/enable or get_cpu/put_cpu.

If the variables are used for a very short time, then the latencies
introduced by a simple:

	var = get_cpu_var(my_var);
	if (var)
		do_something_quick();
	put_cpu_var(my_var);

Otherwise if that do_something_quick(); migrates, it may be doing
something it shouldn't be doing!

-- Steve

--
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/