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Date:	Sun, 3 Jul 2011 08:58:41 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Andrea Righi <andrea@...terlinux.com>
Cc:	Len Brown <lenb@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Florian Mickler <florian@...kler.org>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: fix acpi_power_off lockdep splat

On Saturday, July 02, 2011, Andrea Righi wrote:
> Implement acpi_os_create_lock() as a C-preprocessor macro to assign
> unique lock_class_key to dynamically allocated locks and suppress wrong
> lockdep warnings.
> 
> This fixes:
> https://bugzilla.kernel.org/show_bug.cgi?id=38152
> 
> Reported-by: Borislav Petkov <bp@...en8.de>
> Signed-off-by: Andrea Righi <andrea@...terlinux.com>

So, how exactly does it work?

> ---
>  drivers/acpi/osl.c      |    2 +-
>  include/acpi/acpiosxf.h |   12 +++++++++++-
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 52ca964..2a67602 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -1336,7 +1336,7 @@ EXPORT_SYMBOL(acpi_resources_are_enforced);
>   * Create and initialize a spinlock.
>   */
>  acpi_status
> -acpi_os_create_lock(acpi_spinlock *out_handle)
> +__acpi_os_create_lock(acpi_spinlock *out_handle)
>  {
>  	spinlock_t *lock;
>  
> diff --git a/include/acpi/acpiosxf.h b/include/acpi/acpiosxf.h
> index a756bc8..4a0385d 100644
> --- a/include/acpi/acpiosxf.h
> +++ b/include/acpi/acpiosxf.h
> @@ -99,7 +99,17 @@ acpi_os_table_override(struct acpi_table_header *existing_table,
>   * Spinlock primitives
>   */
>  acpi_status
> -acpi_os_create_lock(acpi_spinlock *out_handle);
> +__acpi_os_create_lock(acpi_spinlock *out_handle);
> +
> +#define acpi_os_create_lock(__handle)			\
> +({							\
> +	acpi_status ret;				\
> +							\
> +	ret = __acpi_os_create_lock(__handle);		\
> +	if (ret == AE_OK)				\
> +		spin_lock_init(*(__handle));		\

It seems that spin_lock_init() has already been done on *__handle, right?

> +	ret;						\
> +})
>  
>  void acpi_os_delete_lock(acpi_spinlock handle);

Rafael
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