sched_ext: scx_qmap: Do not add IMMED to rescue inserts

qmap's stranded fallback forces a task that can run on none of its self cids
onto its first allowed cid with SCX_ENQ_RESCUE, and adds SCX_ENQ_IMMED when
that cid is a time-share it holds. On such a cid the insert stops being a
rescue request:

1. A task is enqueued while none of its allowed cids is in self_cids. At
   attach self_cids is still empty.
2. qmap inserts it into cid 0's local DSQ with SCX_ENQ_RESCUE |
   SCX_ENQ_IMMED.
3. The kernel finds ENQ_IMMED held on cid 0, admits the insert and skips the
   rescue diversion.
4. cid 0's cpu is busy, so the IMMED task is bounced back to qmap with
   SCX_ENQ_REENQ.
5. qmap's enqueue sees the same inputs and repeats step 2. Nothing runs in
   between.
6. The reenqueue limit ejects qmap with SCX_EXIT_ERROR_REENQ.

The caps granted during the parent's ops.sub_attach() are delivered after
the sub already holds its tasks, while the per-cid effective caps that mark
the time-shares are delivered from the first dispatch after bypass lifts, so
every attach that receives a time-share on a task's first allowed cid starts
the loop. Drop IMMED from the rescue inserts so that step 3 diverts to the
rescue path.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

0 files changed, 0 insertions, 0 deletions