linux-kernel - Re: [PATCH 1/2] ACPI / scan: Make namespace scanning and trimming mutually exclusive

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Date:	Sat, 26 Jan 2013 15:19:21 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Steven Newbury <steve@...wbury.org.uk>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jiang Liu <liuj97@...il.com>, Toshi Kani <toshi.kani@...com>
Subject: Re: [PATCH 1/2] ACPI / scan: Make namespace scanning and trimming
 mutually exclusive

On Sat, Jan 26, 2013 at 2:41 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> There is no guarantee that acpi_bus_scan() and acpi_bus_trim() will
> not be run in parallel for the same scope of the ACPI namespace,
> which may lead to a great deal of confusion, so introduce a new mutex
> to prevent that from happening.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

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

Steven,

Can you apply this one to for-pci-res-alloc to check if racing with
docking hotplug/eject
still happen?
or wait one or two days after i rebase that branch.

Thanks

Yinghai

> ---
>  drivers/acpi/scan.c |   16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
> Index: linux-pm/drivers/acpi/scan.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/scan.c
> +++ linux-pm/drivers/acpi/scan.c
> @@ -52,6 +52,7 @@ static const struct acpi_device_id acpi_
>
>  static LIST_HEAD(acpi_device_list);
>  static LIST_HEAD(acpi_bus_id_list);
> +static DEFINE_MUTEX(acpi_scan_lock);
>  DEFINE_MUTEX(acpi_device_lock);
>  LIST_HEAD(acpi_wakeup_device_list);
>
> @@ -1612,19 +1613,22 @@ static acpi_status acpi_bus_device_attac
>  int acpi_bus_scan(acpi_handle handle)
>  {
>         void *device = NULL;
> +       int error = 0;
> +
> +       mutex_lock(&acpi_scan_lock);
>
>         if (ACPI_SUCCESS(acpi_bus_check_add(handle, 0, NULL, &device)))
>                 acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
>                                     acpi_bus_check_add, NULL, NULL, &device);
>
>         if (!device)
> -               return -ENODEV;
> -
> -       if (ACPI_SUCCESS(acpi_bus_device_attach(handle, 0, NULL, NULL)))
> +               error = -ENODEV;
> +       else if (ACPI_SUCCESS(acpi_bus_device_attach(handle, 0, NULL, NULL)))
>                 acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
>                                     acpi_bus_device_attach, NULL, NULL, NULL);
>
> -       return 0;
> +       mutex_unlock(&acpi_scan_lock);
> +       return error;
>  }
>  EXPORT_SYMBOL(acpi_bus_scan);
>
> @@ -1653,6 +1657,8 @@ static acpi_status acpi_bus_remove(acpi_
>
>  void acpi_bus_trim(struct acpi_device *start)
>  {
> +       mutex_lock(&acpi_scan_lock);
> +
>         /*
>          * Execute acpi_bus_device_detach() as a post-order callback to detach
>          * all ACPI drivers from the device nodes being removed.
> @@ -1667,6 +1673,8 @@ void acpi_bus_trim(struct acpi_device *s
>         acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
>                             acpi_bus_remove, NULL, NULL);
>         acpi_bus_remove(start->handle, 0, NULL, NULL);
> +
> +       mutex_unlock(&acpi_scan_lock);
>  }
>  EXPORT_SYMBOL_GPL(acpi_bus_trim);
>
>
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