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    SubjectRe: [RFC PATCH v3 2/3] acpi_memhotplug: Add prepare_remove operation
    At 2012/11/24 1:50, Vasilis Liaskovitis Wrote:
    > Offlining and removal of memory is now done in the prepare_remove callback,
    > not in the remove callback.
    >
    > The prepare_remove callback will be called when trying to remove a memory device
    > with the following ways:
    >
    > 1. send eject request by SCI
    > 2. echo 1>/sys/bus/pci/devices/PNP0C80:XX/eject
    >
    > Note that unbinding the acpi driver from a memory device with:
    > echo "PNP0C80:XX"> /sys/bus/acpi/drivers/acpi_memhotplug/unbind
    >
    > will no longer try to remove the memory. This is in compliance with normal
    > unbind driver core semantics, see the discussion in v2 of this patchset:
    > https://lkml.org/lkml/2012/11/16/649

    If we don't remove it when unbinding it, it may cause kernel panicked.

    I have explained in another mail.

    Thanks
    Wen Congyang

    >
    > After a successful unbind of the driver:
    > - OSPM ejects of the memory device cannot proceed, as acpi_eject_store will
    > return -ENODEV on missing driver.
    > - SCI ejects of the memory device also cannot proceed, as they will also get
    > a "driver data is NULL" error.
    > So the memory can continue to be used safely after unbind.
    >
    > Signed-off-by: Vasilis Liaskovitis<vasilis.liaskovitis@profitbricks.com>
    > ---
    > drivers/acpi/acpi_memhotplug.c | 18 ++++++++++++++++--
    > 1 files changed, 16 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
    > index eb30e5a..d0cfbd9 100644
    > --- a/drivers/acpi/acpi_memhotplug.c
    > +++ b/drivers/acpi/acpi_memhotplug.c
    > @@ -55,6 +55,7 @@ MODULE_LICENSE("GPL");
    >
    > static int acpi_memory_device_add(struct acpi_device *device);
    > static int acpi_memory_device_remove(struct acpi_device *device, int type);
    > +static int acpi_memory_device_prepare_remove(struct acpi_device *device);
    >
    > static const struct acpi_device_id memory_device_ids[] = {
    > {ACPI_MEMORY_DEVICE_HID, 0},
    > @@ -69,6 +70,7 @@ static struct acpi_driver acpi_memory_device_driver = {
    > .ops = {
    > .add = acpi_memory_device_add,
    > .remove = acpi_memory_device_remove,
    > + .prepare_remove = acpi_memory_device_prepare_remove,
    > },
    > };
    >
    > @@ -448,6 +450,20 @@ static int acpi_memory_device_add(struct acpi_device *device)
    > static int acpi_memory_device_remove(struct acpi_device *device, int type)
    > {
    > struct acpi_memory_device *mem_device = NULL;
    > +
    > + if (!device || !acpi_driver_data(device))
    > + return -EINVAL;
    > +
    > + mem_device = acpi_driver_data(device);
    > +
    > + acpi_memory_device_free(mem_device);
    > +
    > + return 0;
    > +}
    > +
    > +static int acpi_memory_device_prepare_remove(struct acpi_device *device)
    > +{
    > + struct acpi_memory_device *mem_device = NULL;
    > int result;
    >
    > if (!device || !acpi_driver_data(device))
    > @@ -459,8 +475,6 @@ static int acpi_memory_device_remove(struct acpi_device *device, int type)
    > if (result)
    > return result;
    >
    > - acpi_memory_device_free(mem_device);
    > -
    > return 0;
    > }
    >


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