On Thursday, November 01, 2012 03:15:31 PM Yinghai Lu wrote:
> On Thu, Nov 1, 2012 at 2:31 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> >> oh, no, that commit should not be reverted. instead we should add some
> >> comment for it...
> >>
> >> that mean : three path, will have three separated static lock dep key
> >> from every INIT_WORK.
> >
> > I see.
> >
> > OK, I'll drop the patch removing it.
> >
> > What about the following comment:
> >
> > "To prevent lockdep from complaining unnecessarily, make sure that there
> > is a different static lockdep key created for each workqueue by using
> > INIT_WORK for each of them separately."
> >
> created ?
>
> how about "defined" ?
>
> or just remove "created"
Yes, that's better.
I suppose that the appended patch may be better still, though.
Thanks,
Rafael
---
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;
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
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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