On Sat 18-03-17 09:57:18, Linus Torvalds wrote: > Tim at al, > I got this on my desktop at shutdown: > > ------------[ cut here ]------------ > kernel BUG at mm/swap_slots.c:270! > invalid opcode: 0000 [#1] SMP > CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1 > Hardware name: System manufacturer System Product Name/Z170-K, BIOS > 1803 05/06/2016 > RIP: 0010:free_swap_slot+0xba/0xd0 > Call Trace: > swap_free+0x36/0x40 > do_swap_page+0x360/0x6d0 > __handle_mm_fault+0x880/0x1080 > handle_mm_fault+0xd0/0x240 > __do_page_fault+0x232/0x4d0 > do_page_fault+0x20/0x70 > page_fault+0x22/0x30 > ---[ end trace aefc9ede53e0ab21 ]--- > > so there seems to be something screwy in the new swap_slots code. I am travelling (LSFMM) so I didn't get to look at this more thoroughly but it seems like a race because enable_swap_slots_cache is called at the very end of the swapon and we could have already created a swap entry for a page by that time I guess. > Any ideas? I'm not finding other reports of this, but I'm also not > seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very > much checks whether swap_slot_cache_initialized has been set, so the > BUG_ON() just seems like garbage. But please take a look. I guess you are right. I cannot speak of the original intention but it seems Tim wanted to be careful to not see unexpected swap entry when the swap wasn't initialized yet. I would just drop the BUG_ON and bail out when the slot cache hasn't been initialized yet. -- Michal Hocko SUSE Labs -- 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>
