Re: [Patch v4 1/7] acpi,memory-hotplug: introduce a mutex lock toprotect the list in acpi_memory_device

[Toshi Kani]

On Thu, 2012-11-08 at 19:04 +0800, Wen Congyang wrote:
> The memory device can be removed by 2 ways:
> 1. send eject request by SCI
> 2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject
> 
> This 2 events may happen at the same time, so we may touch
> acpi_memory_device.res_list at the same time. This patch
> introduce a lock to protect this list.

Hi Wen,

This race condition is not unique in memory hot-remove as the sysfs
eject interface is created for all objects with _EJ0.  For CPU
hot-remove, I addressed this race condition by making the notify handler
to run the hot-remove operation on kacpi_hotplug_wq by calling
acpi_os_hotplug_execute().  This serializes the hot-remove operations
among the two events since the sysfs eject also runs on
kacpi_hotplug_wq.  This way is much simpler and is easy to maintain,
although it does not allow both operations to run simultaneously (which
I do not think we need).  Can it be used for memory hot-remove as well?

Thanks,
-Toshi

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