On Thursday, November 01, 2012 01:17:58 PM Toshi Kani wrote:

On Thu, 2012-11-01 at 11:28 -0700, Yinghai Lu wrote:

quoted

On Thu, Nov 1, 2012 at 9:43 AM, Toshi Kani [off-list ref] wrote:

quoted

Rafael pointed out in my CPU hot-remove patch that
acpi_bus_hot_remove_device() was not exported for modules.  Looks like
you have the same problem here.  FYI, I just sent the following patch
that exports acpi_bus_hot_remove_device() and acpi_os_hotplug_execute().

https://lkml.org/lkml/2012/11/1/225

acpi_os_hotplug_execute() does not like having good quality yet.

c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  941)   /*
c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  942)    * We
can't run hotplug code in keventd_wq/kacpid_wq/kacpid_notify_wq
c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  943)    *
because the hotplug code may call driver .remove() functions,
c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  944)    *
which invoke flush_scheduled_work/acpi_os_wait_events_complete
c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  945)    * to
flush these workqueues.
c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  946)    */
c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  947)   queue
= hp ? kacpi_hotplug_wq :
c02256be (Zhang Rui           2009-06-23 10:20:29 +0800  948)
 (type == OSL_NOTIFY_HANDLER ? kacpi_notify_wq : kacpid_wq);
9ac61856 (Bjorn Helgaas       2009-08-31 22:32:10 +0000  949)
dpc->wait = hp ? 1 : 0;
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  950)
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  951)   if
(queue == kacpi_hotplug_wq)
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  952)
 INIT_WORK(&dpc->work, acpi_os_execute_deferred);
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  953)   else
if (queue == kacpi_notify_wq)
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  954)
 INIT_WORK(&dpc->work, acpi_os_execute_deferred);
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  955)   else
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  956)
 INIT_WORK(&dpc->work, acpi_os_execute_deferred);
bc73675b (Zhang Rui           2010-03-22 15:48:54 +0800  957)

really don't know why checking queue and call same code in every branch.

from comm:

commit bc73675b99fd9850dd914be01d71af99c5d2a1ae
Author: Zhang Rui [off-list ref]
Date:   Mon Mar 22 15:48:54 2010 +0800

    ACPI: fixes a false alarm from lockdep

    fixes a false alarm from lockdep, as acpi hotplug workqueue waits other
    workqueues.
    http://bugzilla.kernel.org/show_bug.cgi?id=14553
    https://bugzilla.kernel.org/show_bug.cgi?id=15521

    Original-patch-from: Andrew Morton [off-list ref]
    Signed-off-by: Shaohua Li [off-list ref]
    Signed-off-by: Zhang Rui [off-list ref]
    Signed-off-by: Len Brown [off-list ref]

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 8e6d866..900da68 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c

@@ -758,7 +758,14 @@ static acpi_status

__acpi_os_execute(acpi_execute_type type,
        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(&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);
+
        ret = queue_work(queue, &dpc->work);

        if (!ret) {


Len or Rafael,
can you just revert that silly patch?

Hi Yinghai,

Per the following thread, the code seems to be written in this way to
allocate a separate lock_class_key for each work queue.  It should have
had some comment to explain this, though.

https://lkml.org/lkml/2009/12/13/304

The code has evolved since then, however, so that it doesn't make sense
any more.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.