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    Subject[PATCH] kdump: Add udev events for memory online/offline
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    Date
    From: Michael Holzheu <holzheu@linux.vnet.ibm.com>

    Currently no udev events for memory hotplug "online" and "offline" are
    generated:

    # udevadm monitor
    # echo offline > /sys/devices/system/memory/memory4/state
    ==> No event

    When kdump is loaded, kexec detects the current memory configuration and
    stores it in the pre-allocated ELF core header. Therefore, for kdump it is
    necessary to reload the kdump kernel with kexec when the memory
    configuration changes (e.g. for online/offline hotplug memory).

    In order to do this automatically, udev rules should be used. This kernel
    patch adds udev events for "online" and "offline". Together with this kernel
    patch, the following udev rules for online/offline have to be added to
    "/etc/udev/rules.d/98-kexec.rules":

    SUBSYSTEM=="memory", ACTION=="online", PROGRAM="/etc/init.d/kdump restart"
    SUBSYSTEM=="memory", ACTION=="offline", PROGRAM="/etc/init.d/kdump restart"

    Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
    ---
    drivers/base/memory.c | 10 +++++++---
    1 file changed, 7 insertions(+), 3 deletions(-)

    --- a/drivers/base/memory.c
    +++ b/drivers/base/memory.c
    @@ -310,11 +310,15 @@ store_mem_state(struct sys_device *dev,

    mem = container_of(dev, struct memory_block, sysdev);

    - if (!strncmp(buf, "online", min((int)count, 6)))
    + if (!strncmp(buf, "online", min((int)count, 6))) {
    ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
    - else if(!strncmp(buf, "offline", min((int)count, 7)))
    + if (ret == 0)
    + kobject_uevent(&dev->kobj, KOBJ_ONLINE);
    + } else if (!strncmp(buf, "offline", min((int)count, 7))) {
    ret = memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
    -
    + if (ret == 0)
    + kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
    + }
    if (ret)
    return ret;
    return count;



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