On Mon, Nov 12, 2012 at 12:00:55PM +0800, Wen Congyang wrote:

At 11/09/2012 02:29 AM, Vasilis Liaskovitis Wrote:

quoted

As discussed in
https://patchwork.kernel.org/patch/1581581/
the driver core remove function needs to always succeed. This means we need
to know that the device can be successfully removed before acpi_bus_trim / 
acpi_bus_hot_remove_device are called. This can cause panics when OSPM-initiated
eject (echo 1 > /sys/bus/acpi/devices/PNP/eject) of memory devices fails, since
the ACPI core goes ahead and ejects the device regardless of whether the memory
is still in use or not.

For this reason a new acpi_device operation called prepare_remove is introduced.
This operation should be registered for acpi devices whose removal (from kernel
perspective) can fail.  Memory devices fall in this category.

acpi_bus_hot_remove_device is changed to handle removal in 2 steps:
- preparation for removal i.e. perform part of removal that can fail outside of
  ACPI core. Should succeed for device and all its children.
- if above step was successfull, proceed to actual ACPI removal

If we unbind the device from the driver, we still need to do preparation. But
you don't do it in your patch.

yes, driver_unbind breaks with the current patchset. I 'll try to fix and
repost. However, I think this will require a new driver-core wide prepare_remove
callback (not only acpi-specific). I am not sure that would be acceptable.

thanks,

- Vasilis

Thanks
Wen Congyang

quoted

acpi_bus_trim is changed accordingly to handle preparation for removal and
actual removal.

With this patchset, only acpi memory devices use the new prepare_remove
device operation. The actual memory removal (VM-related offline and other memory
cleanups) is moved to prepare_remove. The old remove operation just cleans up
the acpi structures. Directly ejecting PNP0C80 memory devices works safely. I
haven't tested yet with an ACPI container which contains memory devices.

Other ACPI devices (e.g. CPU) do not register prepare_remove callbacks, and
their OSPM-side eject should not be affected.

I am not happy with the name prepare_remove. Comments welcome. Let me know if I
should work more in this direction (I think Yasuaki might also look into this
and might have a simpler idea)

Patches are on top of Rafael's linux-pm/linux-next

Vasilis Liaskovitis (3):
  acpi: Introduce prepare_remove operation in acpi_device_ops
  acpi: Make acpi_bus_trim handle device removal preparation
  acpi_memhotplug: Add prepare_remove operation

 drivers/acpi/acpi_memhotplug.c     |   24 +++++++++++++++++++++---
 drivers/acpi/dock.c                |    2 +-
 drivers/acpi/scan.c                |   32 +++++++++++++++++++++++++++++---
 drivers/pci/hotplug/acpiphp_glue.c |    4 ++--
 drivers/pci/hotplug/sgi_hotplug.c  |    2 +-
 include/acpi/acpi_bus.h            |    4 +++-
 6 files changed, 57 insertions(+), 11 deletions(-)

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