Commit cb251eae authored by Cheng-Yang Chou's avatar Cheng-Yang Chou Committed by Tejun Heo
Browse files

tools/sched_ext: Add scx_bpf_sub_dispatch() compat wrapper 



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: default avatarCheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent c50dcf53

tools/sched_ext/include/scx/common.bpf.h

+0 −1
Original line number Diff line number Diff line
@@ -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

tools/sched_ext/include/scx/compat.bpf.h

+13 −0
Original line number Diff line number Diff line
@@ -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.