On Tuesday, March 28, 2017 09:58:08 AM Michal Hocko wrote: > On Mon 20-03-17 22:24:42, Rafael J. Wysocki wrote: > > On Monday, March 20, 2017 03:29:39 PM Michal Hocko wrote: > > > Hi Rafael, > > > > Hi, > > > > > we have been chasing the following BUG() triggering 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(); > > > > > > and it took a while to learn that the issue is caused by > > > /sys/firmware/acpi/hotplug/force_remove being enabled. I was really > > > surprised to see such an option because at least for the memory hotplug > > > it cannot work at all. Memory hotplug fails when the memory is still > > > in use. Even if we do not BUG() here enforcing the hotplug operation > > > will lead to problematic behavior later like crash or a silent memory > > > corruption if the memory gets onlined back and reused by somebody else. > > > > > > I am wondering what was the motivation for introducing this behavior and > > > whether there is a way to disallow it for memory hotplug. Or maybe drop > > > it completely. What would break in such a case? > > > > Honestly, I don't remember from the top of my head and I haven't looked at > > that code for several months. > > > > I need some time to recall that. > > Did you have any chance to look into this? Well, yes. It looks like that was added for some people who depended on the old behavior at that time. I guess we can try to drop it and see what happpens. :-) Thanks, Rafael -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
