sched: Add sched_ext hooks for proxy execution

Proxy execution splits the scheduling context (the donor) from the
execution context (the lock owner). sched_ext needs to observe that
split at three points in __schedule():

 - whether a blocked EXT task can be retained on the runqueue as a
   donor,
 - when a donor's scheduling context starts driving a lock owner,
 - after proxy resolution, when deferred reenqueue work that was blocked
   by an active proxy relationship can be retried.

Introduce scx_allow_proxy_exec(), scx_proxy_donor_start() and
scx_proxy_reenqueue_retry(), and add their call sites in __schedule().
The implementations are empty here and are filled in by the sched_ext
changes that follow, so that all the sched core changes needed by proxy
execution stay together in the preparatory patches.

SCHED_PROXY_EXEC still depends on !SCHED_CLASS_EXT, so the new hooks are
inert: they are compiled out with CONFIG_SCHED_CLASS_EXT=n and
unreachable otherwise.

This is a preparatory change to support proxy execution with sched_ext.
No functional change.

Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260922165445.943315-6-arighi@nvidia.com

0 files changed, 0 insertions, 0 deletions