linux-kernel - Re: [PATCH/RFC 0/4] Add stop_machine_get/put_threads to stop

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <200810091118.27464.rusty@rustcorp.com.au>
Date:	Thu, 9 Oct 2008 11:18:27 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	jens.axboe@...cle.com, schwidefsky@...ibm.com,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH/RFC 0/4] Add stop_machine_get/put_threads to stop_machine infrastructrue.

On Wednesday 08 October 2008 21:14:50 Heiko Carstens wrote:
> On Wed, Oct 08, 2008 at 10:27:04AM +1000, Rusty Russell wrote:
> > OK, idea #2.  Let's just always have a kstopmachine thread running on
> > every online cpu.  Is there a sane way to reuse the workqueue threads for
> > this?
>
> That's a very good idea and what the patch below does. It even simplifies
> the stop_machine code and it does work on an otherwise idle system.
> The only thing that needs to be addressed is that workqueue threads aka
> stop_machine threads are no real time threads now.
> We would need something like create_workqueue_prio() or
> create_workqueue_rt(). Would that be acceptable?

Hmm, I was hoping to reuse the kevent threads rather than create YA set
of threads.  But hey, everyone else is doing it.

> +static struct workqueue_struct *stop_machine_wq;
> +static struct work_struct *stop_machine_work;
> +static struct stop_machine_data active, idle;
> +static cpumask_t active_cpus;

Hmm, please make active cpus a const cpumask_t pointer.  I'm trying to
get rid of these kind of decls in another patch series :)

>  /* This is the actual thread which stops the CPU.  It exits by itself rather
>   * than waiting for kthread_stop(), because it's easier for hotplug CPU. */

This comment is no longer valid...

> +static int __init stop_machine_init(void)
> +{
> +	stop_machine_wq = create_workqueue("kstop");
> +	stop_machine_work = kcalloc(NR_CPUS, sizeof(struct work_struct),
> +				    GFP_KERNEL);

Perhaps make stop_machine_work a per-cpu array of struct work_struct
instead of initializing it here.  Or at least make it a percpu pointer and
only alloc possible cpus.

Does it break cpu hotplug BTW?  That's usually the problem.

But it looks nice!
Rusty.
--
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/