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tools/sched_ext: Add scx_bpf_sub_dispatch() compat wrapper

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Add a transparent compatibility wrapper for the scx_bpf_sub_dispatch()
kfunc in compat.bpf.h. This allows BPF schedulers using the sub-sched
dispatch feature to build and run on older kernels that lack the kfunc.

To avoid requiring code changes in individual schedulers, the
transparent wrapper pattern is used instead of a __COMPAT prefix. The
kfunc is declared with a ___compat suffix, while the static inline
wrapper retains the original scx_bpf_sub_dispatch() name.

When the kfunc is unavailable, the wrapper safely falls back to
returning false. This is acceptable because the dispatch path cannot
do anything useful without underlying sub-sched support anyway.

Tested scx_qmap on v6.14 successfully.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Cheng-Yang Chou
2026-03-23 23:17:33 +08:00
committed by Tejun Heo
parent c50dcf5331
commit cb251eae7b
2 changed files with 13 additions and 1 deletions
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1
tools/sched_ext/include/scx/common.bpf.h
View File

@@ -101,7 +101,6 @@ struct rq *scx_bpf_locked_rq(void) __ksym;
struct task_struct *scx_bpf_cpu_curr(s32 cpu) __ksym __weak;
u64 scx_bpf_now(void) __ksym __weak;
void scx_bpf_events(struct scx_event_stats *events, size_t events__sz) __ksym __weak;
bool scx_bpf_sub_dispatch(u64 cgroup_id) __ksym __weak;
/*
* Use the following as @it__iter when calling scx_bpf_dsq_move[_vtime]() from

13
tools/sched_ext/include/scx/compat.bpf.h
View File

@@ -108,6 +108,19 @@ static inline struct task_struct *__COMPAT_scx_bpf_dsq_peek(u64 dsq_id)
return p;
}
/*
* v7.1: scx_bpf_sub_dispatch() for sub-sched dispatch. Preserve until
* we drop the compat layer for older kernels that lack the kfunc.
*/
bool scx_bpf_sub_dispatch___compat(u64 cgroup_id) __ksym __weak;
static inline bool scx_bpf_sub_dispatch(u64 cgroup_id)
{
if (bpf_ksym_exists(scx_bpf_sub_dispatch___compat))
return scx_bpf_sub_dispatch___compat(cgroup_id);
return false;
}
/**
* __COMPAT_is_enq_cpu_selected - Test if SCX_ENQ_CPU_SELECTED is on
* in a compatible way. We will preserve this __COMPAT helper until v6.16.