Re: [PATCH v1] ACPI / scan: Acquire device_hotplug_lock in acpi_scan_init()

["Rafael J. Wysocki" <rafael@kernel.org>]

On Thu, Jul 25, 2019 at 11:18 AM Oscar Salvador <osalvador@suse.de> wrote:
>
> On Wed, Jul 24, 2019 at 04:30:17PM +0200, David Hildenbrand wrote:
> > We end up calling __add_memory() without the device hotplug lock held.
> > (I used a local patch to assert in __add_memory() that the
> >  device_hotplug_lock is held - I might upstream that as well soon)
> >
> > [   26.771684]        create_memory_block_devices+0xa4/0x140
> > [   26.772952]        add_memory_resource+0xde/0x200
> > [   26.773987]        __add_memory+0x6e/0xa0
> > [   26.775161]        acpi_memory_device_add+0x149/0x2b0
> > [   26.776263]        acpi_bus_attach+0xf1/0x1f0
> > [   26.777247]        acpi_bus_attach+0x66/0x1f0
> > [   26.778268]        acpi_bus_attach+0x66/0x1f0
> > [   26.779073]        acpi_bus_attach+0x66/0x1f0
> > [   26.780143]        acpi_bus_scan+0x3e/0x90
> > [   26.780844]        acpi_scan_init+0x109/0x257
> > [   26.781638]        acpi_init+0x2ab/0x30d
> > [   26.782248]        do_one_initcall+0x58/0x2cf
> > [   26.783181]        kernel_init_freeable+0x1bd/0x247
> > [   26.784345]        kernel_init+0x5/0xf1
> > [   26.785314]        ret_from_fork+0x3a/0x50
> >
> > So perform the locking just like in acpi_device_hotplug().
> >
> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> > Cc: Len Brown <lenb@kernel.org
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Oscar Salvador <osalvador@suse.de>
> > Cc: Michal Hocko <mhocko@suse.com>
> > Signed-off-by: David Hildenbrand <david@redhat.com>
>
> Given that that call comes from a __init function, so while booting, I wonder
> how bad it is.

Yes, it probably does not matter.

> Anyway, let us be consistent:

Right.