For non root CG, in try_charge(), we keep trying to charge until we succeed. On non-preemptive kernel, when we are OOM, this results in holding CPU forever. On SMP systems, this doesn't create a big problem because oom_reaper get a change to kill victim and make some free pages. However on a single-core CPU (or cases where oom_reaper pinned to same CPU where try_charge is executing), oom_reaper shall never get scheduled and we stay in try_charge forever. Steps to repo this on non-smp: 1. mount -t tmpfs none /sys/fs/cgroup 2. mkdir /sys/fs/cgroup/memory 3. mount -t cgroup none /sys/fs/cgroup/memory -o memory 4. mkdir /sys/fs/cgroup/memory/0 5. echo 40M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes 6. echo $$ > /sys/fs/cgroup/memory/0/tasks 7. stress -m 5 --vm-bytes 10M --vm-hang 0 Signed-off-by: Julius Hemanth Pitti <jpitti@xxxxxxxxx> --- mm/memcontrol.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0d6f3ea86738..4620d70267cb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2652,6 +2652,8 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, if (fatal_signal_pending(current)) goto force; + cond_resched(); + /* * keep retrying as long as the memcg oom killer is able to make * a forward progress or bypass the charge if the oom killer -- 2.17.1
