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sched_ext: Fix scx_bpf_dsq_insert() backward binary compatibility

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cded46d971 ("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: cded46d971 ("sched_ext: Make scx_bpf_dsq_insert*() return bool")
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo
2025-10-21 10:39:24 -10:00
parent 67fa319f5f
commit 2dbbdeda77
2 changed files with 11 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
kernel/sched/ext.c
View File

@@ -5421,8 +5421,8 @@ __bpf_kfunc_start_defs();
* scheduler, %false return triggers scheduler abort and the caller doesn't need
* to check the return value.
*/
__bpf_kfunc bool scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice,
u64 enq_flags)
__bpf_kfunc bool scx_bpf_dsq_insert___v2(struct task_struct *p, u64 dsq_id,
u64 slice, u64 enq_flags)
{
struct scx_sched *sch;
@@ -5445,12 +5445,12 @@ __bpf_kfunc bool scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice
}
/*
* COMPAT: Will be removed in v6.23.
* COMPAT: Will be removed in v6.23 along with the ___v2 suffix.
*/
__bpf_kfunc void scx_bpf_dsq_insert___compat(struct task_struct *p, u64 dsq_id,
__bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id,
u64 slice, u64 enq_flags)
{
scx_bpf_dsq_insert(p, dsq_id, slice, enq_flags);
scx_bpf_dsq_insert___v2(p, dsq_id, slice, enq_flags);
}
static bool scx_dsq_insert_vtime(struct scx_sched *sch, struct task_struct *p,
@@ -5546,7 +5546,7 @@ __bpf_kfunc_end_defs();
BTF_KFUNCS_START(scx_kfunc_ids_enqueue_dispatch)
BTF_ID_FLAGS(func, scx_bpf_dsq_insert, KF_RCU)
BTF_ID_FLAGS(func, scx_bpf_dsq_insert___compat, KF_RCU)
BTF_ID_FLAGS(func, scx_bpf_dsq_insert___v2, KF_RCU)
BTF_ID_FLAGS(func, __scx_bpf_dsq_insert_vtime, KF_RCU)
BTF_ID_FLAGS(func, scx_bpf_dsq_insert_vtime, KF_RCU)
BTF_KFUNCS_END(scx_kfunc_ids_enqueue_dispatch)

10
tools/sched_ext/include/scx/compat.bpf.h
View File

@@ -238,16 +238,16 @@ scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime
* v6.19: scx_bpf_dsq_insert() now returns bool instead of void. Move
* scx_bpf_dsq_insert() decl to common.bpf.h and drop compat helper after v6.22.
*/
bool scx_bpf_dsq_insert___new(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak;
void scx_bpf_dsq_insert___compat(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak;
bool scx_bpf_dsq_insert___v2(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak;
void scx_bpf_dsq_insert___v1(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak;
static inline bool
scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags)
{
if (bpf_ksym_exists(scx_bpf_dsq_insert___new)) {
return scx_bpf_dsq_insert___new(p, dsq_id, slice, enq_flags);
if (bpf_ksym_exists(scx_bpf_dsq_insert___v2)) {
return scx_bpf_dsq_insert___v2(p, dsq_id, slice, enq_flags);
} else {
scx_bpf_dsq_insert___compat(p, dsq_id, slice, enq_flags);
scx_bpf_dsq_insert___v1(p, dsq_id, slice, enq_flags);
return true;
}
}