linux-kernel - Re: [PATCH][resubmit] x86: enable preemption in delay

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:	Sun, 1 Jun 2008 18:25:17 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Marin Mitov <mitov@...p.bas.bg>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-rt-users <linux-rt-users@...r.kernel.org>, akpm@...l.org,
	Ingo Molnar <mingo@...e.hu>,
	Clark Williams <clark.williams@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi-suse@...stfloor.org>
Subject: Re: [PATCH][resubmit] x86: enable preemption in delay

>  static void delay_tsc(unsigned long loops)
>  {
> -	unsigned long bclock, now;
> +	unsigned prev, prev_1, now;
> +	unsigned left = loops;
> +	unsigned prev_cpu, cpu;
> +
> +	preempt_disable();
> +	rdtscl(prev);


The unsigneds should be probably u64  and the rdtsc rdtscll.
Otherwise this will all overflow for longer waits on a very
fast systems (e.g. a 5Ghz system wraps 32bit in ~1.1 seconds)
Normally such delays shouldn't be that long, but why risk
overflow even in extreme cases?

-Andi
--
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/