linux-kernel - Re: [PATCH 11/15] x86: Rewrite cyc2ns to avoid the need to disable IRQs

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] [day] [month] [year] [list]

Date:	Tue, 17 Jun 2014 17:32:26 +0100
From:	Mauro <registosites@...mail.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Arjan van de Ven <arjan@...ux.intel.com>,
	Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Eliezer Tamir <eliezer.tamir@...ux.intel.com>,
	Zhang Rui <rui.zhang@...el.com>, jacob.jun.pan@...ux.intel.com,
	Mike Galbraith <bitbucket@...ine.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	Andy Lutomirski <luto@...capital.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Srivatsa S. Bhat" <srivatsa@....edu>
Subject: Re: [PATCH 11/15] x86: Rewrite cyc2ns to avoid the need to disable
 IRQs

On 17-06-2014 13:42, Viresh Kumar wrote:
>> So what you can try is force a cyc2ns read before the write in
>> set_cyc2ns_scale(). I think its possible that if we do not do the read,
>> the write will wait for a 'free' slot indefinitely.
> 
> Hmm, I see. Thanks for your quick response.
> 
> Are you suggesting something like this ? :
> 
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 57e5ce1..290ac03 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -249,6 +249,9 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
>         if (!cpu_khz)
>                 goto done;
> 
> +       data = cyc2ns_read_begin();
> +       cyc2ns_read_end(data);
> +
>         data = cyc2ns_write_begin(cpu);
> 
>         rdtscll(tsc_now);
> 
> 
> @Mauro: Please try this once Peter confirms.

I have tried this and it doesn't solve the problem, the machine still
hangs after the second frequency change after cpu offline/online.
--
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/