On Fri 28-10-11 15:23:47, Andrew Morton wrote: > From: Michal Hocko <mhocko@xxxxxxx> > Subject: oom: do not live lock on frozen tasks > > Konstantin Khlebnikov has reported (https://lkml.org/lkml/2011/8/23/45) > that OOM can end up in a live lock if select_bad_process picks up a frozen > task. > > Unfortunately we cannot mark such processes as unkillable to ignore them > because we could panic the system even though there is a chance that > somebody could thaw the process so we can make a forward process (e.g. a > process from another cpuset or with a different nodemask). > > Let's thaw an OOM selected frozen process right after we've sent fatal > signal from oom_kill_task. > > Thawing is safe if the frozen task doesn't access any suspended device > (e.g. by ioctl) on the way out to the userspace where we handle the > signal and die. Note, we are not interested in the kernel threads because > they are not oom killable. > > Accessing suspended devices by a userspace processes shouldn't be an issue > because devices are suspended only after userspace is already frozen and > oom is disabled at that time. > > Other than that userspace accesses the fridge only from the signal > handling routines so we are able to handle SIGKILL without any negative > side effects or we always check for pending signals after we return from > try_to_freeze (e.g. in lguest). The patch is not needed after we have oom-thaw-threads-if-oom-killed-thread-is-frozen-before-deferring.patch which is already in the -mm tree (http://permalink.gmane.org/gmane.linux.kernel.mm/69138, the whole email thread started here: http://comments.gmane.org/gmane.linux.kernel.mm/69003). So you can drop this one. > > Signed-off-by: Michal Hocko <mhocko@xxxxxxx> > Reported-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Acked-by: Rafael J. Wysocki <rjw@xxxxxxx> > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > mm/oom_kill.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff -puN mm/oom_kill.c~oom-do-not-live-lock-on-frozen-tasks mm/oom_kill.c > --- a/mm/oom_kill.c~oom-do-not-live-lock-on-frozen-tasks > +++ a/mm/oom_kill.c > @@ -462,10 +462,15 @@ static int oom_kill_task(struct task_str > task_pid_nr(q), q->comm); > task_unlock(q); > force_sig(SIGKILL, q); > + > + if (frozen(q)) > + thaw_process(q); > } > > set_tsk_thread_flag(p, TIF_MEMDIE); > force_sig(SIGKILL, p); > + if (frozen(p)) > + thaw_process(p); > > return 0; > } > _ > Subject: Subject: oom: do not live lock on frozen tasks > > Patches currently in -mm which might be from mhocko@xxxxxxx are > > origin.patch > linux-next.patch > mm-compaction-trivial-clean-up-in-acct_isolated.patch > mm-change-isolate-mode-from-define-to-bitwise-type.patch > mm-compaction-make-isolate_lru_page-filter-aware.patch > mm-compaction-make-isolate_lru_page-filter-aware-fix.patch > mm-zone_reclaim-make-isolate_lru_page-filter-aware.patch > mm-zone_reclaim-make-isolate_lru_page-filter-aware-fix.patch > mm-migration-clean-up-unmap_and_move.patch > mm-page-writebackc-make-determine_dirtyable_memory-static-again.patch > oom-avoid-killing-kthreads-if-they-assume-the-oom-killed-threads-mm.patch > mm-vmscan-drop-nr_force_scan-from-get_scan_count.patch > mm-mmapc-eliminate-the-ret-variable-from-mm_take_all_locks.patch > oom-thaw-threads-if-oom-killed-thread-is-frozen-before-deferring.patch > oom-do-not-live-lock-on-frozen-tasks.patch > cgroup-kmemleak-annotate-alloc_page-for-cgroup-allocations.patch > memcg-rename-mem-variable-to-memcg.patch > memcg-fix-oom-schedule_timeout.patch > memcg-do-not-expose-uninitialized-mem_cgroup_per_node-to-world.patch > memcg-close-race-between-charge-and-putback.patch > -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>