[PATCHSET v2 sched_ext/for-7.3] sched_ext: Sub-scheduler follow-ups

[Tejun Heo <tj@kernel.org>]

Hello,

v2: - Host scx_dispatch_sched() in a new inlines.h rather than at the end of
      internal.h, which formed a circular include with cid.h (sashiko AI),
      and drop sub.h's now-unused cid.h include.

v1: https://lore.kernel.org/r/20260714230917.84158-1-tj@kernel.org

Follow-ups to the sub-scheduler capability series, addressing two things
Andrea raised while reviewing v5[1]: sched teardown drained queued ecaps
syncs with an msleep() poll loop, and with CONFIG_EXT_SUB_SCHED=y hot paths
keep paying for sub-sched bookkeeping even when no sub-scheduler exists.

Patch 0001 replaces the teardown poll loop with direct removal from the
llist. Patches 0002-0003 are prep and 0004 adds the scx_has_subs static key
and gates the sub-sched portions of hot paths on it.

[1] https://lore.kernel.org/r/20260709225041.1695495-1-tj@kernel.org

Based on sched_ext/for-7.3 (35f9cbbacb67).

This patchset contains the following 4 patches.

 0001 sched_ext: Remove queued ecaps syncs directly on sched teardown
 0002 sched_ext: Move scx_dispatch_sched() to a new inlines.h
 0003 sched_ext: Gate sub_dispatch_prev with CONFIG_EXT_SUB_SCHED
 0004 sched_ext: Add the scx_has_subs static key and gate sub-sched hot paths

The patchset is also available in the following git branch:

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-sub-followups-v2

diffstat follows. Thanks.

 kernel/sched/build_policy.c |   1 +
 kernel/sched/ext/ext.c      |   7 ++-
 kernel/sched/ext/idle.c     |  10 ++++
 kernel/sched/ext/inlines.h  | 128 ++++++++++++++++++++++++++++++++++++++++++++
 kernel/sched/ext/internal.h |  19 ++++++-
 kernel/sched/ext/sub.c      |  89 ++++++++++++++++++++----------
 kernel/sched/ext/sub.h      | 125 ++++++------------------------------------
 kernel/sched/sched.h        |   3 +-
 8 files changed, 240 insertions(+), 142 deletions(-)

--
tejun