Re: [PATCH v2] sched/proxy: allow SCHED_PROXY_EXEC with PREEMPT_RT

[Quchaosheng]

Fair enough - I will stop here.

To be explicit about the current state so nobody spends time on it: the
series is withdrawn. v2 only made the combination build and boot; it did
not make proxy execution functional on PREEMPT_RT, because a task's
blocked_on is only ever set by the native mutex slow path, which is
compiled out when PREEMPT_RT is set. So the option would have produced a
kernel where task_is_blocked() is always false and find_proxy_task() is
never reached, which is exactly the "build option that is effectively
broken" you describe.

The build failures themselves are real and are still in the tree
(kernel/sched/core.c with both options set), so the Kconfig "depends on
!PREEMPT_RT" is correct as it stands. Making SCHED_PROXY_EXEC meaningful
under PREEMPT_RT would mean teaching the RT mutex implementation to
maintain blocked_on, which is a separate piece of work and not something
I am proposing here.

Thanks for the review, and for the earlier round with Sebastian.

Quchaosheng