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SubjectRe: [PATCH 2/2]ACPI: assign different lockdep key for acpi works
On Fri, 11 Dec 2009 11:04:58 +0800
Shaohua Li <shaohua.li@intel.com> wrote:

> Differentiate works for three different workqueue in ACPI. This fixes
> a fase alarm from lockdep, as acpi hotplug workqueue waits other
> workqueues.
>
> http://bugzilla.kernel.org/show_bug.cgi?id=14553
>
> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> ---
> drivers/acpi/osl.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> Index: linux/drivers/acpi/osl.c
> ===================================================================
> --- linux.orig/drivers/acpi/osl.c 2009-12-10 10:40:15.000000000 +0800
> +++ linux/drivers/acpi/osl.c 2009-12-10 10:43:25.000000000 +0800
> @@ -729,6 +729,8 @@ static acpi_status __acpi_os_execute(acp
> struct acpi_os_dpc *dpc;
> struct workqueue_struct *queue;
> int ret;
> + static struct lock_class_key hp_key, notify_key, acpid_key;
> +
> ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
> "Scheduling function [%p(%p)] for deferred execution.\n",
> function, context));
> @@ -758,7 +760,15 @@ static acpi_status __acpi_os_execute(acp
> 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_KEY(&dpc->work, acpi_os_execute_deferred,
> + hp_key, "acpi_hp_work");
> + else if (queue == kacpi_notify_wq)
> + INIT_WORK_KEY(&dpc->work, acpi_os_execute_deferred,
> + notify_key, "acpi_notify_work");
> + else
> + INIT_WORK_KEY(&dpc->work, acpi_os_execute_deferred,
> + acpid_key, "acpi_acpid_work");
> ret = queue_work(queue, &dpc->work);
>
> if (!ret) {

Yes, that's a shortcoming in the present INIT_WORK(). However I think
you can solve this more simply, without introducing INIT_WORK_KEY():

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);

it looks silly, but I think the compiler will do the right thing with it
- you'll get a separate lock_class_key at each site.

Obviously it would need an explanatory comment.


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