[PATCH 1/3] driver core: Support asynchronous driver shutdown

[Jeremy Allison]

Good catch. Thanks. I'll fix that and re-submit.

On Wed, Dec 13, 2023 at 5:59 AM Sagi Grimberg <sagi at grimberg.me> wrote:
>
> > From: Tanjore Suresh <tansuresh at google.com>
> >
> > This changes the bus driver interface with additional entry points
> > to enable devices to implement asynchronous shutdown. The existing
> > synchronous interface to shutdown is unmodified and retained for
> > backward compatibility.
> >
> > This changes the common device shutdown code to enable devices to
> > participate in asynchronous shutdown implementation.
> >
> > Signed-off-by: Tanjore Suresh <tansuresh at google.com>
> > ---
> >   drivers/base/core.c        | 39 +++++++++++++++++++++++++++++++++++++-
> >   include/linux/device/bus.h | 10 ++++++++++
> >   2 files changed, 48 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index 67ba592afc77..d9745822fb50 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -4725,6 +4725,7 @@ EXPORT_SYMBOL_GPL(device_change_owner);
> >   void device_shutdown(void)
> >   {
> >       struct device *dev, *parent;
> > +     LIST_HEAD(async_shutdown_list);
> >
> >       wait_for_device_probe();
> >       device_block_probing();
> > @@ -4769,7 +4770,14 @@ void device_shutdown(void)
> >                               dev_info(dev, "shutdown_pre\n");
> >                       dev->class->shutdown_pre(dev);
> >               }
> > -             if (dev->bus && dev->bus->shutdown) {
> > +
> > +             if (dev->bus && dev->bus->shutdown_pre) {
>
> I'm assuming that there is no shutdown_pre without a shutdown_post
> paired with it, so I think the code should verify that.
>
> > +                     if (initcall_debug)
> > +                             dev_info(dev, "shutdown_pre\n");
> > +                     dev->bus->shutdown_pre(dev);
> > +                     list_add(&dev->kobj.entry,
> > +                             &async_shutdown_list);
> > +             } else if (dev->bus && dev->bus->shutdown) {
> >                       if (initcall_debug)
> >                               dev_info(dev, "shutdown\n");
> >                       dev->bus->shutdown(dev);
> > @@ -4789,6 +4797,35 @@ void device_shutdown(void)
> >               spin_lock(&devices_kset->list_lock);
> >       }
> >       spin_unlock(&devices_kset->list_lock);
> > +
> > +     /*
> > +      * Second pass spin for only devices, that have configured
> > +      * Asynchronous shutdown.
> > +      */
> > +     while (!list_empty(&async_shutdown_list)) {
> > +             dev = list_entry(async_shutdown_list.next, struct device,
> > +                             kobj.entry);
> > +             parent = get_device(dev->parent);
> > +             get_device(dev);
> > +             /*
> > +              * Make sure the device is off the  list
> > +              */
> > +             list_del_init(&dev->kobj.entry);
> > +             if (parent)
> > +                     device_lock(parent);
> > +             device_lock(dev);
> > +             if (dev->bus && dev->bus->shutdown_post) {
> > +                     if (initcall_debug)
> > +                             dev_info(dev,
> > +                             "shutdown_post called\n");
> > +                     dev->bus->shutdown_post(dev);
> > +             }
> > +             device_unlock(dev);
> > +             if (parent)
> > +                     device_unlock(parent);
> > +             put_device(dev);
> > +             put_device(parent);
> > +     }
> >   }
> >
> >   /*
> > diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
> > index ae10c4322754..cbcb001f6336 100644
> > --- a/include/linux/device/bus.h
> > +++ b/include/linux/device/bus.h
> > @@ -48,6 +48,14 @@ struct fwnode_handle;
> >    *          will never get called until they do.
> >    * @remove: Called when a device removed from this bus.
> >    * @shutdown:       Called at shut-down time to quiesce the device.
> > + * @shutdown_pre:    Called at the shutdown-time to start the shutdown
> > + *                   process on the device. This entry point will be called
> > + *                   only when the bus driver has indicated it would like
> > + *                   to participate in asynchronous shutdown completion.
> > + * @shutdown_post:   Called at shutdown-time  to complete the shutdown
> > + *                   process of the device. This entry point will be called
> > + *                   only when the bus drive has indicated it would like to
> > + *                   participate in the asynchronous shutdown completion.
> >    *
> >    * @online: Called to put the device back online (after offlining it).
> >    * @offline:        Called to put the device offline for hot-removal. May fail.
> > @@ -90,6 +98,8 @@ struct bus_type {
> >       void (*sync_state)(struct device *dev);
> >       void (*remove)(struct device *dev);
> >       void (*shutdown)(struct device *dev);
> > +     void (*shutdown_pre)(struct device *dev);
> > +     void (*shutdown_post)(struct device *dev);
> >
> >       int (*online)(struct device *dev);
> >       int (*offline)(struct device *dev);