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Make sched_ext reject retained donors by default. Implement scx_allow_proxy_exec() to force blocked EXT tasks through the regular block path in schedule(). Also fully deactivate any retained proxy donor in sched_change_begin() before changing its scheduling class. This prevents sched_setscheduler(), PI transitions and sched_ext activation from carrying an existing proxy session into the new class. Some RT/DL PI transitions could usefully preserve the proxy session. For example, an RT waiter can boost a FAIR donor which is itself blocked on a non-PI mutex; retaining the donor would allow the boosted context to keep proxy-executing that mutex owner. Doing so safely requires defining which scheduling classes can carry retained proxy state across a transition. Keep the conservative reset for now and leave compatible RT/DL PI chains for future work. This is a preparatory change to support proxy execution with sched_ext. Signed-off-by: Andrea Righi --- kernel/sched/core.c | 9 +++++++++ kernel/sched/ext/ext.c | 2 +- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ea432bf307c1d..23e92db0d2c74 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -11295,6 +11295,15 @@ sched_change_begin(struct task_struct *p, const struct sched_class *next_class, flags |= DEQUEUE_NOCLOCK; } + /* + * Don't carry retained proxy state across scheduling class changes. + * Compatible RT/DL PI transitions could preserve the session so that a + * boosted donor continues proxy-executing its lock owner. Defining which + * class transitions can safely retain that state is left for future work. + */ + if ((flags & DEQUEUE_CLASS) && next_class != p->sched_class) + sched_proxy_block_task(rq, p); + if ((flags & DEQUEUE_CLASS) && p->sched_class->switching_from) p->sched_class->switching_from(rq, p); diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 6b1d9c98b8efa..7bbe3c2e243af 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -26,7 +26,7 @@ DEFINE_RAW_SPINLOCK(scx_sched_lock); bool scx_allow_proxy_exec(const struct task_struct *p) { - return true; + return p->sched_class != &ext_sched_class; } /* -- 2.55.0