Re: [PATCH v3 3/3] Improve container_notify_cb() to support container hot-remove.

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Thursday, November 01, 2012 01:16:22 PM Yinghai Lu wrote:
> On Thu, Nov 1, 2012 at 1:17 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Thursday, November 01, 2012 01:17:58 PM Toshi Kani wrote:
> >> On Thu, 2012-11-01 at 11:28 -0700, Yinghai Lu wrote:
> >> > On Thu, Nov 1, 2012 at 9:43 AM, Toshi Kani <toshi.kani@hp.com> wrote:
> >> > >
> >> > > 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 <rui.zhang@intel.com>
> >> > 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 <akpm@linux-foundation.org>
> >> >     Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> >> >     Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> >> >     Signed-off-by: Len Brown <len.brown@intel.com>
> >> >
> >> > 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.
> >
> 
> 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."

Thanks,
Rafael


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