sched/core: Remove redundant core_sched_seq

core_sched_seq records whether an rq has consumed the pick made by the
last core-wide selection.

However, rq->core_pick already carries the same per-rq state. A core-wide
selection leaves core_pick populated only for siblings which still need to
consume their picks. It is cleared when the current CPU consumes its pick,
when a sibling is already running the selected task, or when a pending pick
is consumed through the fastpath. The CPU offline path clears it as well.

core_task_seq and core_pick_seq serve a separate purpose. core_task_seq
changes when the task set changes and for each new core-wide pick, while
core_pick_seq records the task sequence on which the selection was made.
Their equality therefore establishes that a pending core_pick is still
valid.

Consequently, once core_pick_seq == core_task_seq, a non-NULL core_pick is
sufficient to tell that this rq still has a pick to consume.
core_sched_seq duplicates that pending/consumed state.

Remove core_sched_seq and use core_pick directly as the pending marker.

Testing included an instrumented comparison of the old and new pending
predicates under core-scheduling stress. Additional guest tests exercised
repeated core-cookie lifecycles, forced idle, and CPU hotplug under load.
No predicate divergence or kernel warning was observed.

Signed-off-by: Hui Su <sh_def@163.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260915163138.2973969-1-sh_def@163.com

0 files changed, 0 insertions, 0 deletions