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 01:17:58 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.

Thanks,
Rafael


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