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

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Date:	Thu, 1 Nov 2012 16:39:50 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Toshi Kani <toshi.kani@...com>, ZhangRui <rui.zhang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>,
	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, Nov 1, 2012 at 4:15 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: ACPI: Make seemingly useless check in osl.c more understandable
>
> There is a seemingly useless check in drivers/acpi/osl.c added by
> commit bc73675 (ACPI: fixes a false alarm from lockdep), which really
> is necessary to avoid false positive lockdep complaints.  Document
> this and rearrange the code related to it so that it makes fewer
> checks.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/osl.c |   21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
>
> Index: linux/drivers/acpi/osl.c
> ===================================================================
> --- linux.orig/drivers/acpi/osl.c
> +++ linux/drivers/acpi/osl.c
> @@ -944,17 +944,24 @@ static acpi_status __acpi_os_execute(acp
>          * because the hotplug code may call driver .remove() functions,
>          * which invoke flush_scheduled_work/acpi_os_wait_events_complete
>          * to flush these workqueues.
> +        *
> +        * To prevent lockdep from complaining unnecessarily, make sure that
> +        * there is a different static lockdep key for each workqueue by using
> +        * INIT_WORK() for each of them separately.
>          */
> -       queue = hp ? kacpi_hotplug_wq :
> -               (type == OSL_NOTIFY_HANDLER ? kacpi_notify_wq : kacpid_wq);
> -       dpc->wait = hp ? 1 : 0;
> -
> -       if (queue == kacpi_hotplug_wq)
> +       if (hp) {
> +               queue = kacpi_hotplug_wq;
> +               dpc->wait = 1;
>                 INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> -       else if (queue == kacpi_notify_wq)
> +       } else if (type == OSL_NOTIFY_HANDLER) {
> +               queue = kacpi_notify_wq;
> +               dpc->wait = 0;

yes, much clear.

at the same can you changne
dpc allocation from kmalloc with kzalloc instead.

then we save two lines for dpc->wait = 0

After that

Acked-by: Yinghai Lu <yinghai@...nel.org>

>                 INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> -       else
> +       } else {
> +               queue = kacpid_wq;
> +               dpc->wait = 0;
>                 INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> +       }
>
>         /*
>          * On some machines, a software-initiated SMI causes corruption unless
>
> --
--
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