From: Tejun Heo Date: Wed, 29 Oct 2025 18:35:25 +0000 (-1000) Subject: sched_ext/tools: Restore backward compat with v6.12 kernels X-Git-Tag: v6.19-rc1~177^2~23 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=34423456443c5cf5ad5180155f7d40f96b836194;p=thirdparty%2Fkernel%2Flinux.git sched_ext/tools: Restore backward compat with v6.12 kernels Commit 111a79800aed ("tools/sched_ext: Strip compatibility macros for cgroup and dispatch APIs") removed the compat layer for v6.12-v6.13 kfunc renaming, but v6.12 is the current LTS kernel and will remain supported through 2026. Restore backward compatibility so schedulers built with v6.19+ headers can run on v6.12 kernels. The restored compat differs from the original in two ways: 1. Uses ___new/___old suffixes instead of ___compat for clarity. The new macros check for v6.13+ names (scx_bpf_dsq_move*), fall back to v6.12 names (scx_bpf_dispatch_from_dsq*, scx_bpf_consume), then return safe no-ops for missing symbols. 2. Integrates with the args-struct-packing changes added in c0d630ba347c ("sched_ext: Wrap kfunc args in struct to prepare for aux__prog"). scx_bpf_dsq_insert_vtime() now tries __scx_bpf_dsq_insert_vtime (args struct), then scx_bpf_dsq_insert_vtime___compat (v6.13-v6.18), then scx_bpf_dispatch_vtime___compat (pre-v6.13). Forward compatibility is not restored - binaries built against v6.13 or earlier headers won't run on v6.19+ kernels, as the old kfunc names are not exported. This is acceptable since the priority is new binaries running on older kernels. Also add missing compat checks for ops.cgroup_set_bandwidth() (added v6.17) and ops.cgroup_set_idle() (added v6.19). These need to be NULLed out in userspace on older kernels. Reported-by: Andrea Righi Acked-and-tested-by: Andrea Righi Signed-off-by: Tejun Heo --- diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h index 82a798c3fb222..821d5791bd422 100644 --- a/tools/sched_ext/include/scx/common.bpf.h +++ b/tools/sched_ext/include/scx/common.bpf.h @@ -65,11 +65,6 @@ s32 __scx_bpf_select_cpu_and(struct task_struct *p, const struct cpumask *cpus_a bool __scx_bpf_dsq_insert_vtime(struct task_struct *p, struct scx_bpf_dsq_insert_vtime_args *args) __ksym __weak; u32 scx_bpf_dispatch_nr_slots(void) __ksym; void scx_bpf_dispatch_cancel(void) __ksym; -bool scx_bpf_dsq_move_to_local(u64 dsq_id) __ksym __weak; -void scx_bpf_dsq_move_set_slice(struct bpf_iter_scx_dsq *it__iter, u64 slice) __ksym __weak; -void scx_bpf_dsq_move_set_vtime(struct bpf_iter_scx_dsq *it__iter, u64 vtime) __ksym __weak; -bool scx_bpf_dsq_move(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __ksym __weak; -bool scx_bpf_dsq_move_vtime(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __ksym __weak; void scx_bpf_kick_cpu(s32 cpu, u64 flags) __ksym; s32 scx_bpf_dsq_nr_queued(u64 dsq_id) __ksym; void scx_bpf_destroy_dsq(u64 dsq_id) __ksym; @@ -104,7 +99,6 @@ s32 scx_bpf_task_cpu(const struct task_struct *p) __ksym; struct rq *scx_bpf_cpu_rq(s32 cpu) __ksym; struct rq *scx_bpf_locked_rq(void) __ksym; struct task_struct *scx_bpf_cpu_curr(s32 cpu) __ksym __weak; -struct cgroup *scx_bpf_task_cgroup(struct task_struct *p) __ksym __weak; u64 scx_bpf_now(void) __ksym __weak; void scx_bpf_events(struct scx_event_stats *events, size_t events__sz) __ksym __weak; diff --git a/tools/sched_ext/include/scx/compat.bpf.h b/tools/sched_ext/include/scx/compat.bpf.h index 0bfb8abe2a46a..f2969c3061a75 100644 --- a/tools/sched_ext/include/scx/compat.bpf.h +++ b/tools/sched_ext/include/scx/compat.bpf.h @@ -15,6 +15,65 @@ __ret; \ }) +/* v6.12: 819513666966 ("sched_ext: Add cgroup support") */ +struct cgroup *scx_bpf_task_cgroup___new(struct task_struct *p) __ksym __weak; + +#define scx_bpf_task_cgroup(p) \ + (bpf_ksym_exists(scx_bpf_task_cgroup___new) ? \ + scx_bpf_task_cgroup___new((p)) : NULL) + +/* + * v6.13: The verb `dispatch` was too overloaded and confusing. kfuncs are + * renamed to unload the verb. + * + * scx_bpf_dispatch_from_dsq() and friends were added during v6.12 by + * 4c30f5ce4f7a ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()"). + */ +bool scx_bpf_dsq_move_to_local___new(u64 dsq_id) __ksym __weak; +void scx_bpf_dsq_move_set_slice___new(struct bpf_iter_scx_dsq *it__iter, u64 slice) __ksym __weak; +void scx_bpf_dsq_move_set_vtime___new(struct bpf_iter_scx_dsq *it__iter, u64 vtime) __ksym __weak; +bool scx_bpf_dsq_move___new(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __ksym __weak; +bool scx_bpf_dsq_move_vtime___new(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __ksym __weak; + +bool scx_bpf_consume___old(u64 dsq_id) __ksym __weak; +void scx_bpf_dispatch_from_dsq_set_slice___old(struct bpf_iter_scx_dsq *it__iter, u64 slice) __ksym __weak; +void scx_bpf_dispatch_from_dsq_set_vtime___old(struct bpf_iter_scx_dsq *it__iter, u64 vtime) __ksym __weak; +bool scx_bpf_dispatch_from_dsq___old(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __ksym __weak; +bool scx_bpf_dispatch_vtime_from_dsq___old(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __ksym __weak; + +#define scx_bpf_dsq_move_to_local(dsq_id) \ + (bpf_ksym_exists(scx_bpf_dsq_move_to_local___new) ? \ + scx_bpf_dsq_move_to_local___new((dsq_id)) : \ + scx_bpf_consume___old((dsq_id))) + +#define scx_bpf_dsq_move_set_slice(it__iter, slice) \ + (bpf_ksym_exists(scx_bpf_dsq_move_set_slice___new) ? \ + scx_bpf_dsq_move_set_slice___new((it__iter), (slice)) : \ + (bpf_ksym_exists(scx_bpf_dispatch_from_dsq_set_slice___old) ? \ + scx_bpf_dispatch_from_dsq_set_slice___old((it__iter), (slice)) : \ + (void)0)) + +#define scx_bpf_dsq_move_set_vtime(it__iter, vtime) \ + (bpf_ksym_exists(scx_bpf_dsq_move_set_vtime___new) ? \ + scx_bpf_dsq_move_set_vtime___new((it__iter), (vtime)) : \ + (bpf_ksym_exists(scx_bpf_dispatch_from_dsq_set_vtime___old) ? \ + scx_bpf_dispatch_from_dsq_set_vtime___old((it__iter), (vtime)) : \ + (void)0)) + +#define scx_bpf_dsq_move(it__iter, p, dsq_id, enq_flags) \ + (bpf_ksym_exists(scx_bpf_dsq_move___new) ? \ + scx_bpf_dsq_move___new((it__iter), (p), (dsq_id), (enq_flags)) : \ + (bpf_ksym_exists(scx_bpf_dispatch_from_dsq___old) ? \ + scx_bpf_dispatch_from_dsq___old((it__iter), (p), (dsq_id), (enq_flags)) : \ + false)) + +#define scx_bpf_dsq_move_vtime(it__iter, p, dsq_id, enq_flags) \ + (bpf_ksym_exists(scx_bpf_dsq_move_vtime___new) ? \ + scx_bpf_dsq_move_vtime___new((it__iter), (p), (dsq_id), (enq_flags)) : \ + (bpf_ksym_exists(scx_bpf_dispatch_vtime_from_dsq___old) ? \ + scx_bpf_dispatch_vtime_from_dsq___old((it__iter), (p), (dsq_id), (enq_flags)) : \ + false)) + /* * v6.15: 950ad93df2fc ("bpf: add kfunc for populating cpumask bits") * @@ -166,12 +225,16 @@ static inline struct task_struct *__COMPAT_scx_bpf_cpu_curr(int cpu) * replaced with variants that pack scalar arguments in a struct. Wrappers are * provided to maintain source compatibility. * + * v6.13: scx_bpf_dsq_insert_vtime() renaming is also handled here. See the + * block on dispatch renaming above for more details. + * * The kernel will carry the compat variants until v6.23 to maintain binary * compatibility. After v6.23 release, remove the compat handling and move the * wrappers to common.bpf.h. */ s32 scx_bpf_select_cpu_and___compat(struct task_struct *p, s32 prev_cpu, u64 wake_flags, const struct cpumask *cpus_allowed, u64 flags) __ksym __weak; +void scx_bpf_dispatch_vtime___compat(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime, u64 enq_flags) __ksym __weak; void scx_bpf_dsq_insert_vtime___compat(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime, u64 enq_flags) __ksym __weak; /** @@ -227,10 +290,14 @@ scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime }; return __scx_bpf_dsq_insert_vtime(p, &args); - } else { + } else if (bpf_ksym_exists(scx_bpf_dsq_insert_vtime___compat)) { scx_bpf_dsq_insert_vtime___compat(p, dsq_id, slice, vtime, enq_flags); return true; + } else { + scx_bpf_dispatch_vtime___compat(p, dsq_id, slice, vtime, + enq_flags); + return true; } } @@ -239,18 +306,25 @@ scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime * scx_bpf_dsq_insert() decl to common.bpf.h and drop compat helper after v6.22. * The extra ___compat suffix is to work around libbpf not ignoring __SUFFIX on * kernel side. The entire suffix can be dropped later. + * + * v6.13: scx_bpf_dsq_insert() renaming is also handled here. See the block on + * dispatch renaming above for more details. */ bool scx_bpf_dsq_insert___v2___compat(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; +void scx_bpf_dispatch___compat(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___v2___compat)) { return scx_bpf_dsq_insert___v2___compat(p, dsq_id, slice, enq_flags); - } else { + } else if (bpf_ksym_exists(scx_bpf_dsq_insert___v1)) { scx_bpf_dsq_insert___v1(p, dsq_id, slice, enq_flags); return true; + } else { + scx_bpf_dispatch___compat(p, dsq_id, slice, enq_flags); + return true; } } diff --git a/tools/sched_ext/include/scx/compat.h b/tools/sched_ext/include/scx/compat.h index 35c67c5174ac0..8b4897fc8b998 100644 --- a/tools/sched_ext/include/scx/compat.h +++ b/tools/sched_ext/include/scx/compat.h @@ -151,6 +151,10 @@ static inline long scx_hotplug_seq(void) * * ec7e3b0463e1 ("implement-ops") in https://github.com/sched-ext/sched_ext is * the current minimum required kernel version. + * + * COMPAT: + * - v6.17: ops.cgroup_set_bandwidth() + * - v6.19: ops.cgroup_set_idle() */ #define SCX_OPS_OPEN(__ops_name, __scx_name) ({ \ struct __scx_name *__skel; \ @@ -162,6 +166,16 @@ static inline long scx_hotplug_seq(void) SCX_BUG_ON(!__skel, "Could not open " #__scx_name); \ __skel->struct_ops.__ops_name->hotplug_seq = scx_hotplug_seq(); \ SCX_ENUM_INIT(__skel); \ + if (__skel->struct_ops.__ops_name->cgroup_set_bandwidth && \ + !__COMPAT_struct_has_field("sched_ext_ops", "cgroup_set_bandwidth")) { \ + fprintf(stderr, "WARNING: kernel doesn't support ops.cgroup_set_bandwidth()\n"); \ + __skel->struct_ops.__ops_name->cgroup_set_bandwidth = NULL; \ + } \ + if (__skel->struct_ops.__ops_name->cgroup_set_idle && \ + !__COMPAT_struct_has_field("sched_ext_ops", "cgroup_set_idle")) { \ + fprintf(stderr, "WARNING: kernel doesn't support ops.cgroup_set_idle()\n"); \ + __skel->struct_ops.__ops_name->cgroup_set_idle = NULL; \ + } \ __skel; \ })