On Thursday, November 01, 2012 04:39:50 PM Yinghai Lu wrote:
> On Thu, Nov 1, 2012 at 4:15 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > 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@xxxxxxxxx>
> > ---
> > 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
Good idea. :-)
> After that
>
> Acked-by: Yinghai Lu <yinghai@xxxxxxxxxx>
For completeness:
---
From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
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@xxxxxxxxx>
Acked-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
drivers/acpi/osl.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
Index: linux/drivers/acpi/osl.c
===================================================================
--- linux.orig/drivers/acpi/osl.c
+++ linux/drivers/acpi/osl.c
@@ -932,7 +932,7 @@ static acpi_status __acpi_os_execute(acp
* having a static work_struct.
*/
- dpc = kmalloc(sizeof(struct acpi_os_dpc), GFP_ATOMIC);
+ dpc = kzalloc(sizeof(struct acpi_os_dpc), GFP_ATOMIC);
if (!dpc)
return AE_NO_MEMORY;
@@ -944,17 +944,22 @@ 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;
INIT_WORK(&dpc->work, acpi_os_execute_deferred);
- else
+ } else {
+ queue = kacpid_wq;
INIT_WORK(&dpc->work, acpi_os_execute_deferred);
+ }
/*
* On some machines, a software-initiated SMI causes corruption unless
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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