linux-kernel - Re: [PATCH v3 3/3] Improve container_notify

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Date:	Thu, 01 Nov 2012 13:17:58 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	ZhangRui <rui.zhang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Tang Chen <tangchen@...fujitsu.com>, bhelgaas@...gle.com,
	jiang.liu@...wei.com, izumi.taku@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] Improve container_notify_cb() to support
 container hot-remove.

On Thu, 2012-11-01 at 11:28 -0700, Yinghai Lu wrote:
> On Thu, Nov 1, 2012 at 9:43 AM, Toshi Kani <toshi.kani@...com> wrote:
> >
> > Rafael pointed out in my CPU hot-remove patch that
> > acpi_bus_hot_remove_device() was not exported for modules.  Looks like
> > you have the same problem here.  FYI, I just sent the following patch
> > that exports acpi_bus_hot_remove_device() and acpi_os_hotplug_execute().
> >
> > https://lkml.org/lkml/2012/11/1/225
> 
> acpi_os_hotplug_execute() does not like having good quality yet.
> 
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  941)   /*
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  942)    * We
> can't run hotplug code in keventd_wq/kacpid_wq/kacpid_notify_wq
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  943)    *
> because the hotplug code may call driver .remove() functions,
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  944)    *
> which invoke flush_scheduled_work/acpi_os_wait_events_complete
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  945)    * to
> flush these workqueues.
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  946)    */
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  947)   queue
> = hp ? kacpi_hotplug_wq :
> c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  948)
>  (type == OSL_NOTIFY_HANDLER ? kacpi_notify_wq : kacpid_wq);
> 9ac61856 (Bjorn Helgaas       2009-08-31 22:32:10 +0000  949)
> dpc->wait = hp ? 1 : 0;
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  950)
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  951)   if
> (queue == kacpi_hotplug_wq)
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  952)
>  INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  953)   else
> if (queue == kacpi_notify_wq)
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  954)
>  INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  955)   else
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  956)
>  INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  957)
> 
> really don't know why checking queue and call same code in every branch.
> 
> from comm:
> 
> commit bc73675b99fd9850dd914be01d71af99c5d2a1ae
> Author: Zhang Rui <rui.zhang@...el.com>
> Date:   Mon Mar 22 15:48:54 2010 +0800
> 
>     ACPI: fixes a false alarm from lockdep
> 
>     fixes a false alarm from lockdep, as acpi hotplug workqueue waits other
>     workqueues.
>     http://bugzilla.kernel.org/show_bug.cgi?id=14553
>     https://bugzilla.kernel.org/show_bug.cgi?id=15521
> 
>     Original-patch-from: Andrew Morton <akpm@...ux-foundation.org>
>     Signed-off-by: Shaohua Li <shaohua.li@...el.com>
>     Signed-off-by: Zhang Rui <rui.zhang@...el.com>
>     Signed-off-by: Len Brown <len.brown@...el.com>
> 
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 8e6d866..900da68 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -758,7 +758,14 @@ static acpi_status
> __acpi_os_execute(acpi_execute_type type,
>         queue = hp ? kacpi_hotplug_wq :
>                 (type == OSL_NOTIFY_HANDLER ? kacpi_notify_wq : kacpid_wq);
>         dpc->wait = hp ? 1 : 0;
> -       INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> +
> +       if (queue == kacpi_hotplug_wq)
> +               INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> +       else if (queue == kacpi_notify_wq)
> +               INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> +       else
> +               INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> +
>         ret = queue_work(queue, &dpc->work);
> 
>         if (!ret) {
> 
> 
> Len or Rafael,
> can you just revert that silly patch?

Hi Yinghai,

Per the following thread, the code seems to be written in this way to
allocate a separate lock_class_key for each work queue.  It should have
had some comment to explain this, though.

https://lkml.org/lkml/2009/12/13/304

Thanks,
-Toshi



> 
> Yinghai


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