linux-kernel - Re: [PATCH v3 3/3] Improve container_notify

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Date:	Fri, 02 Nov 2012 00:15:35 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Toshi Kani <toshi.kani@...com>, ZhangRui <rui.zhang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>,
	Tang Chen <tangchen@...fujitsu.com>, bhelgaas@...gle.com,
	jiang.liu@...wei.com, izumi.taku@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] Improve container_notify_cb() to support container hot-remove.

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@...k.pl> 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@...el.com>
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@...el.com>
---
 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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