Messages in this thread | | | Subject | Re: [PATCH] mm/memory_hotplug: drain per-cpu pages again during memory offline | From | Vlastimil Babka <> | Date | Thu, 3 Sep 2020 15:50:20 +0200 |
| |
On 9/1/20 2:46 PM, Pavel Tatashin wrote: > There is a race during page offline that can lead to infinite loop: > a page never ends up on a buddy list and __offline_pages() keeps > retrying infinitely or until a termination signal is received. > > Thread#1 - a new process: > > load_elf_binary > begin_new_exec > exec_mmap > mmput > exit_mmap > tlb_finish_mmu > tlb_flush_mmu > release_pages > free_unref_page_list > free_unref_page_prepare > set_pcppage_migratetype(page, migratetype); > // Set page->index migration type below MIGRATE_PCPTYPES > > Thread#2 - hot-removes memory > __offline_pages > start_isolate_page_range > set_migratetype_isolate > set_pageblock_migratetype(page, MIGRATE_ISOLATE); > Set migration type to MIGRATE_ISOLATE-> set > drain_all_pages(zone); > // drain per-cpu page lists to buddy allocator. > > Thread#1 - continue > free_unref_page_commit > migratetype = get_pcppage_migratetype(page); > // get old migration type > list_add(&page->lru, &pcp->lists[migratetype]); > // add new page to already drained pcp list > > Thread#2 > Never drains pcp again, and therefore gets stuck in the loop. > > The fix is to try to drain per-cpu lists again after > check_pages_isolated_cb() fails. > > Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> > Cc: stable@vger.kernel.org
Fixes: ? Acked-by: Vlastimil Babka <vbabka@suse.cz>
Thanks.
| |