[RFC 00/60] Coscheduling for Linux

[Jan H. Schönherr]

On 09/12/2018 09:34 PM, Jan H. Schönherr wrote:
> That said, I see a hang, too. It seems to happen, when there is a
> cpu.scheduled!=0 group that is not a direct child of the root task group.
> You seem to have "/sys/fs/cgroup/cpu/machine" as an intermediate group.
> (The case ==0 within !=0 within the root task group works for me.)
> 
> I'm going to dive into the code.

With the patch below (which technically changes patch 55/60), the hang I 
experienced is gone.

Please let me know, if it works for you as well.

Regards
Jan


diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8da2033596ff..2d8b3f9a275f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7189,23 +7189,26 @@ pick_next_task_fair(struct rq *rq, struct task_struct 
*prev, struct rq_flags *rf
                while (!(cfs_rq = is_same_group(se, pse))) {
                        int se_depth = se->depth;
                        int pse_depth = pse->depth;
+                       bool work = false;

-                       if (se_depth <= pse_depth && leader_of(pse) == cpu) {
+                       if (se_depth <= pse_depth && __leader_of(pse) == cpu) {
                                put_prev_entity(cfs_rq_of(pse), pse);
                                pse = parent_entity(pse);
+                               work = true;
                        }
-                       if (se_depth >= pse_depth && leader_of(se) == cpu) {
+                       if (se_depth >= pse_depth && __leader_of(se) == cpu) {
                                set_next_entity(cfs_rq_of(se), se);
                                se = parent_entity(se);
+                               work = true;
                        }
-                       if (leader_of(pse) != cpu && leader_of(se) != cpu)
+                       if (!work)
                                break;
                }

-               if (leader_of(pse) == cpu)
-                       put_prev_entity(cfs_rq, pse);
-               if (leader_of(se) == cpu)
-                       set_next_entity(cfs_rq, se);
+               if (__leader_of(pse) == cpu)
+                       put_prev_entity(cfs_rq_of(pse), pse);
+               if (__leader_of(se) == cpu)
+                       set_next_entity(cfs_rq_of(se), se);
        }

        goto done;