sched_ext: Fix scx_bpf_dsq_insert() backward binary compatibility

cded46d97159 ("sched_ext: Make scx_bpf_dsq_insert*() return bool")
introduced a new bool-returning scx_bpf_dsq_insert() and renamed the old
void-returning version to scx_bpf_dsq_insert___compat, with the expectation
that libbpf would match old binaries to the ___compat variant, maintaining
backward binary compatibility. However, while libbpf ignores ___suffix on
the BPF side when matching symbols, it doesn't do so for kernel-side symbols.
Old binaries compiled with the original scx_bpf_dsq_insert() could no longer
resolve the symbol.

Fix by reversing the naming: Keep scx_bpf_dsq_insert() as the old
void-returning interface and add ___v2 to the new bool-returning version.
This allows old binaries to continue working while new code can use the
___v2 variant. Once libbpf is updated to ignore kernel-side ___SUFFIX, the
___v2 suffix can be dropped when the compat interface is removed.

v2: Use ___v2 instead of ___new.

Fixes: cded46d97159 ("sched_ext: Make scx_bpf_dsq_insert*() return bool")
Signed-off-by: Tejun Heo <tj@kernel.org>

Tejun Heo 8 months ago 2dbbdeda 67fa319f

+11 -11

2 changed files

expand all

kernel

sched

ext.c

tools

sched_ext

include

scx

compat.bpf.h

+6 -6

kernel/sched/ext.c

··· 5421 5421 * scheduler, %false return triggers scheduler abort and the caller doesn't need 5422 5422 * to check the return value. 5423 5423 */ 5424 - __bpf_kfunc bool scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice, 5425 - u64 enq_flags) 5424 + __bpf_kfunc bool scx_bpf_dsq_insert___v2(struct task_struct *p, u64 dsq_id, 5425 + u64 slice, u64 enq_flags) 5426 5426 { 5427 5427 struct scx_sched *sch; 5428 5428 ··· 5445 5445 } 5446 5446 5447 5447 /* 5448 - * COMPAT: Will be removed in v6.23. 5448 + * COMPAT: Will be removed in v6.23 along with the ___v2 suffix. 5449 5449 */ 5450 - __bpf_kfunc void scx_bpf_dsq_insert___compat(struct task_struct *p, u64 dsq_id, 5450 + __bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, 5451 5451 u64 slice, u64 enq_flags) 5452 5452 { 5453 - scx_bpf_dsq_insert(p, dsq_id, slice, enq_flags); 5453 + scx_bpf_dsq_insert___v2(p, dsq_id, slice, enq_flags); 5454 5454 } 5455 5455 5456 5456 static bool scx_dsq_insert_vtime(struct scx_sched *sch, struct task_struct *p, ··· 5546 5546 5547 5547 BTF_KFUNCS_START(scx_kfunc_ids_enqueue_dispatch) 5548 5548 BTF_ID_FLAGS(func, scx_bpf_dsq_insert, KF_RCU) 5549 - BTF_ID_FLAGS(func, scx_bpf_dsq_insert___compat, KF_RCU) 5549 + BTF_ID_FLAGS(func, scx_bpf_dsq_insert___v2, KF_RCU) 5550 5550 BTF_ID_FLAGS(func, __scx_bpf_dsq_insert_vtime, KF_RCU) 5551 5551 BTF_ID_FLAGS(func, scx_bpf_dsq_insert_vtime, KF_RCU) 5552 5552 BTF_KFUNCS_END(scx_kfunc_ids_enqueue_dispatch)

+5 -5

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

··· 238 238 * v6.19: scx_bpf_dsq_insert() now returns bool instead of void. Move 239 239 * scx_bpf_dsq_insert() decl to common.bpf.h and drop compat helper after v6.22. 240 240 */ 241 - bool scx_bpf_dsq_insert___new(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak; 242 - void scx_bpf_dsq_insert___compat(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak; 241 + bool scx_bpf_dsq_insert___v2(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak; 242 + void scx_bpf_dsq_insert___v1(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak; 243 243 244 244 static inline bool 245 245 scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) 246 246 { 247 - if (bpf_ksym_exists(scx_bpf_dsq_insert___new)) { 248 - return scx_bpf_dsq_insert___new(p, dsq_id, slice, enq_flags); 247 + if (bpf_ksym_exists(scx_bpf_dsq_insert___v2)) { 248 + return scx_bpf_dsq_insert___v2(p, dsq_id, slice, enq_flags); 249 249 } else { 250 - scx_bpf_dsq_insert___compat(p, dsq_id, slice, enq_flags); 250 + scx_bpf_dsq_insert___v1(p, dsq_id, slice, enq_flags); 251 251 return true; 252 252 } 253 253 }

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