sched_ext: scx_qmap: Restore unused idle claims from ops.dispatch()

Browse source

scx_qmap tracks idle cids itself. pick_direct_dispatch_cid() claims a cid by
clearing its bit and the task is inserted into that cid's local DSQ, which
kicks the CPU. When the task does not arrive, for example because the insert
fell back to the global DSQ after an affinity change, the CPU wakes, finds
nothing and picks idle again. That is not an idle transition, so
ops.update_idle() is not called and the cid stays marked busy until an
unrelated task runs on it.

Restore the claim from ops.dispatch(). The kick guarantees a dispatch on the
kicked CPU, and when it finds nothing to run with a NULL @prev, the CPU is
going back to idle. Document the pattern in ops.update_idle(), which reports
only actual transitions.

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

...

This commit is contained in:

Tejun Heo 2026-09-14 22:12:34 -10:00

parent c7a1c6e800

commit 9a0b159ff1

2 changed files with 16 additions and 4 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

6

kernel/sched/ext/internal.h

View file

14

tools/sched_ext/scx_qmap.bpf.c

View file