linux/Documentation/ABI/obsolete
Michal Hocko ffc10d82ff ACPI / scan: Drop support for force_remove
/sys/firmware/acpi/hotplug/force_remove was presumably added to support
auto offlining in the past. This is, however, inherently dangerous for
some hotplugable resources like memory. The memory offlining fails when
the memory is still in use and cannot be dropped or migrated. If we
ignore the failure we are basically allowing for subtle memory
corruption or a crash.

We have actually noticed the later while hitting BUG() during the memory
hotremove (remove_memory):
	ret = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL,
			check_memblock_offlined_cb);
	if (ret)
		BUG();

it took us quite non-trivial time realize that the customer had
force_remove enabled. Even if the BUG was removed here and we could
propagate the error up the call chain it wouldn't help at all because
then we would hit a crash or a memory corruption later and harder to
debug. So force_remove is unfixable for the memory hotremove. We haven't
checked other hotplugable resources to be prone to a similar problems.

Remove the force_remove functionality because it is not fixable currently.
Keep the sysfs file and report an error if somebody tries to enable it.
Encourage users to report about the missing functionality and work with
them with an alternative solution.

Reviewed-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2017-04-13 03:51:47 +02:00
..
proc-sys-vm-nr_pdflush_threads mm: prepare for removal of obsolete /proc/sys/vm/nr_pdflush_threads 2012-07-31 18:42:40 -07:00
sysfs-bus-usb USB: deprecate the power/level sysfs attribute 2010-05-20 13:21:37 -07:00
sysfs-driver-hid-roccat-arvo HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-isku HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-koneplus HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-konepure HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-kovaplus HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-lua HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-pyra HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-ryos HID: roccat: Fixed resubmit: Deprecating most Roccat sysfs attributes 2015-10-21 11:54:42 +02:00
sysfs-driver-hid-roccat-savu Documentation: fix common spelling mistakes 2016-04-28 07:51:59 -06:00
sysfs-firmware-acpi ACPI / scan: Drop support for force_remove 2017-04-13 03:51:47 +02:00
sysfs-gpio gpio: ABI: mark the sysfs ABI as obsolete 2016-02-09 11:09:55 +01:00