quoted

quoted

Consider the following sequence of operations for a hotplugged memory
device:

1. echo "PNP0C80:XX" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind
2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject

If we don't offline/remove the memory, we have no chance to do it in
step 2. After
step2, the memory is used by the kernel, but we have powered off it. It
is very
dangerous.

How does power-off happen after unbind? acpi_eject_store checks for existing
driver before taking any action:

#ifndef FORCE_EJECT
	if (acpi_device->driver == NULL) {
		ret = -ENODEV;
		goto err;
	}
#endif

FORCE_EJECT is not defined afaict, so the function returns without scheduling
acpi_bus_hot_remove_device. Is there another code path that calls power-off?

Consider the following case:

We hotremove the memory device by SCI and unbind it from the driver at the same time:

CPUa                                                  CPUb
acpi_memory_device_notify()
                                       unbind it from the driver
    acpi_bus_hot_remove_device()

Can we make acpi_bus_remove() to fail if a given acpi_device is not
bound with a driver?  If so, can we make the unbind operation to perform
unbind only?

Thanks,
-Toshi


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>