Re: [PATCH 2/2] ACPI: scan: Fix _STA getting called on devices with unmet dependencies

Rafael J. Wysocki
2021-03-29T14:56:47Z

On Mon, Mar 29, 2021 at 4:46 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Hi,
>
> On 3/29/21 3:39 PM, Rafael J. Wysocki wrote:
> > On Sunday, March 28, 2021 1:20:00 PM CEST Hans de Goede wrote:
> >> Commit 71da201f38df ("ACPI: scan: Defer enumeration of devices with
> >> _DEP lists") dropped the following 2 lines from acpi_init_device_object():
> >>
> >> /* Assume there are unmet deps until acpi_device_dep_initialize() runs */
> >> device->dep_unmet = 1;
> >>
> >> Leaving the initial value of dep_unmet at the 0 from the kzalloc(). This
> >> causes the acpi_bus_get_status() call in acpi_add_single_object() to
> >> actually call _STA, even though there maybe unmet deps, leading to errors
> >> like these:
> >>
> >> [ 0.123579] ACPI Error: No handler for Region [ECRM] (00000000ba9edc4c)
> >> [GenericSerialBus] (20170831/evregion-166)
> >> [ 0.123601] ACPI Error: Region GenericSerialBus (ID=9) has no handler
> >> (20170831/exfldio-299)
> >> [ 0.123618] ACPI Error: Method parse/execution failed
> >> \_SB.I2C1.BAT1._STA, AE_NOT_EXIST (20170831/psparse-550)
> >>
> >> Fix this by moving the acpi_scan_dep_init() call done for devices added
> >> during the second pass done by acpi_bus_scan() to inside
> >> acpi_add_single_object(), so that dep_unmet is properly initialized
> >> before the acpi_bus_get_status() call.
> >
> > I wonder why the change below can't be made instead.
> >
> > The behavior would be closer to the original then AFAICS.
>
> Right the behavior would be closer to the code before the 2 fase scan
> rework. But just actually making sure we have the right value in unmet_dep
> a tiny bit earlier seems cleaner to me.
>
> Note that the one acpi_add_single_object() call which actually sets the
> new init_dep parameter to true and the previous place of calling
> acpi_scan_dep_init() are very close together, here is the code before
> this patch:
>
> acpi_add_single_object(&device, handle, type, sta, !check_dep);
> if (!device)
> return AE_CTRL_DEPTH;
>
> acpi_scan_init_hotplug(device);
> if (!check_dep)
> acpi_scan_dep_init();
>
> So we are only doing the acpi_scan_dep_init() call a tiny bit earlier
> and wrt which locks are being held when it gets called no changes are
> made since it is still called as part of the call-graph below
> acpi_bus_check_add(), I explicitly checked the locking situation because
> that was my one worry with this patch.
>
> And this new approach also has the advantage of not setting dep_unmet=1
> (and never clearing it) for devices instantiated through:
>
> acpi_bus_register_early_device()
> acpi_bus_scan_fixed()
> acpi_add_power_resource()
>
> IOW while looking into fixing the regression of the errors being logged
> again I tried to do a cleaner fix then last time.
>
> With that said if you prefer the version you suggest let me know and I'll
> post a single v2 patch doing things that way.

I'd prefer to do the simple fix at this stage of the development
cycle, so yes, please.

I agree that it would be better to initialize dep_unmet properly in
acpi_add_single_object(), but I'd do that a bit differently.

> If you want to go with your suggestion, shall I then add a dep_unmet=0
> statement to the 3 mentioned functions which leave it at 1 when going back
> to the old way of handling this ?

No, I'll take care of this separately.

Cheers!