On Monday, April 10, 2017 07:13:44 PM Michal Hocko wrote: > On Mon 03-04-17 09:40:23, Michal Hocko wrote: > > From: Michal Hocko <mhocko@xxxxxxxx> > > > > /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@xxxxxxxx> > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > > ping on this? /shrug/ I'll apply it if nobody has any problems with it. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
