From: Aaron Tomlin <atomlin@xxxxxxxxxx> Subject: mm/page_alloc: bail out on fatal signal during reclaim/compaction retry attempt A customer experienced a low-memory situation and decided to issue a SIGKILL (i.e. a fatal signal). Instead of promptly terminating as one would expect, the aforementioned task remained unresponsive. Further investigation indicated that the task was "stuck" in the reclaim/compaction retry loop. Now, it does not make sense to retry compaction when a fatal signal is pending. In the context of try_to_compact_pages(), indeed COMPACT_SKIPPED can be returned; albeit, not every zone, on the zone list, would be considered in the case a fatal signal is found to be pending. Yet, in should_compact_retry(), given the last known compaction result, each zone, on the zone list, can be considered/or checked (see compaction_zonelist_suitable()). For example, if a zone was found to succeed, then reclaim/compaction would be tried again (notwithstanding the above). This patch ensures that compaction is not needlessly retried irrespective of the last known compaction result e.g. if it was skipped, in the unlikely case a fatal signal is found pending. So, OOM is at least attempted. Link: https://lkml.kernel.org/r/20210520142901.3371299-1-atomlin@xxxxxxxxxx Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/page_alloc.c~mm-page_alloc-bail-out-on-fatal-signal-during-reclaim-compaction-retry-attempt +++ a/mm/page_alloc.c @@ -4251,6 +4251,9 @@ should_compact_retry(struct alloc_contex if (!order) return false; + if (fatal_signal_pending(current)) + return false; + if (compaction_made_progress(compact_result)) (*compaction_retries)++; _
