| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20251007015147.2496026-5-tj@kernel.org>
Date: Mon, 6 Oct 2025 15:51:47 -1000
From: Tejun Heo <tj@...nel.org>
To: David Vernet <void@...ifault.com>,
Andrea Righi <arighi@...dia.com>,
Changwoo Min <changwoo@...lia.com>
Cc: linux-kernel@...r.kernel.org,
sched-ext@...ts.linux.dev,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 4/4] sched_ext: Make scx_bpf_dsq_insert*() return bool
In preparation for hierarchical schedulers, change scx_bpf_dsq_insert() and
scx_bpf_dsq_insert_vtime() to return bool instead of void. With
sub-schedulers, there will be no reliable way to guarantee a task is still
owned by the sub-scheduler at insertion time (e.g., the task may have been
migrated to another scheduler). The bool return value will enable
sub-schedulers to detect and gracefully handle insertion failures.
For the root scheduler, insertion failures will continue to trigger scheduler
abort via scx_error(), so existing code doesn't need to check the return
value. Backward compatibility is maintained through compat wrappers.
Also update scx_bpf_dsq_move() documentation to clarify that it can return
false for sub-schedulers when @dsq_id points to a disallowed local DSQ.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/sched/ext.c | 45 ++++++++++++++++++------
tools/sched_ext/include/scx/common.bpf.h | 3 +-
tools/sched_ext/include/scx/compat.bpf.h | 23 ++++++++++--
3 files changed, 56 insertions(+), 15 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index a34e731229de..399e53c8939c 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -5323,8 +5323,12 @@ __bpf_kfunc_start_defs();
* exhaustion. If zero, the current residual slice is maintained. If
* %SCX_SLICE_INF, @p never expires and the BPF scheduler must kick the CPU with
* scx_bpf_kick_cpu() to trigger scheduling.
+ *
+ * Returns %true on successful insertion, %false on failure. On the root
+ * scheduler, %false return triggers scheduler abort and the caller doesn't need
+ * to check the return value.
*/
-__bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice,
+__bpf_kfunc bool scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice,
u64 enq_flags)
{
struct scx_sched *sch;
@@ -5332,10 +5336,10 @@ __bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice
guard(rcu)();
sch = rcu_dereference(scx_root);
if (unlikely(!sch))
- return;
+ return false;
if (!scx_dsq_insert_preamble(sch, p, enq_flags))
- return;
+ return false;
if (slice)
p->scx.slice = slice;
@@ -5343,13 +5347,24 @@ __bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice
p->scx.slice = p->scx.slice ?: 1;
scx_dsq_insert_commit(sch, p, dsq_id, enq_flags);
+
+ return true;
+}
+
+/*
+ * COMPAT: Will be removed in v6.23.
+ */
+__bpf_kfunc void scx_bpf_dsq_insert___compat(struct task_struct *p, u64 dsq_id,
+ u64 slice, u64 enq_flags)
+{
+ scx_bpf_dsq_insert(p, dsq_id, slice, enq_flags);
}
-static void scx_dsq_insert_vtime(struct scx_sched *sch, struct task_struct *p,
+static bool scx_dsq_insert_vtime(struct scx_sched *sch, struct task_struct *p,
u64 dsq_id, u64 slice, u64 vtime, u64 enq_flags)
{
if (!scx_dsq_insert_preamble(sch, p, enq_flags))
- return;
+ return false;
if (slice)
p->scx.slice = slice;
@@ -5359,6 +5374,8 @@ static void scx_dsq_insert_vtime(struct scx_sched *sch, struct task_struct *p,
p->scx.dsq_vtime = vtime;
scx_dsq_insert_commit(sch, p, dsq_id, enq_flags | SCX_ENQ_DSQ_PRIQ);
+
+ return true;
}
struct scx_bpf_dsq_insert_vtime_args {
@@ -5394,8 +5411,12 @@ struct scx_bpf_dsq_insert_vtime_args {
* function must not be called on a DSQ which already has one or more FIFO tasks
* queued and vice-versa. Also, the built-in DSQs (SCX_DSQ_LOCAL and
* SCX_DSQ_GLOBAL) cannot be used as priority queues.
+ *
+ * Returns %true on successful insertion, %false on failure. On the root
+ * scheduler, %false return triggers scheduler abort and the caller doesn't need
+ * to check the return value.
*/
-__bpf_kfunc void
+__bpf_kfunc bool
__scx_bpf_dsq_insert_vtime(struct task_struct *p,
struct scx_bpf_dsq_insert_vtime_args *args)
{
@@ -5405,10 +5426,10 @@ __scx_bpf_dsq_insert_vtime(struct task_struct *p,
sch = rcu_dereference(scx_root);
if (unlikely(!sch))
- return;
+ return false;
- scx_dsq_insert_vtime(sch, p, args->dsq_id, args->slice, args->vtime,
- args->enq_flags);
+ return scx_dsq_insert_vtime(sch, p, args->dsq_id, args->slice,
+ args->vtime, args->enq_flags);
}
/*
@@ -5432,6 +5453,7 @@ __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_vtime, KF_RCU)
BTF_ID_FLAGS(func, scx_bpf_dsq_insert_vtime, KF_RCU)
BTF_KFUNCS_END(scx_kfunc_ids_enqueue_dispatch)
@@ -5686,8 +5708,9 @@ __bpf_kfunc void scx_bpf_dsq_move_set_vtime(struct bpf_iter_scx_dsq *it__iter,
* Can be called from ops.dispatch() or any BPF context which doesn't hold a rq
* lock (e.g. BPF timers or SYSCALL programs).
*
- * Returns %true if @p has been consumed, %false if @p had already been consumed
- * or dequeued.
+ * Returns %true if @p has been consumed, %false if @p had already been
+ * consumed, dequeued, or, for sub-scheds, @dsq_id points to a disallowed local
+ * DSQ.
*/
__bpf_kfunc bool scx_bpf_dsq_move(struct bpf_iter_scx_dsq *it__iter,
struct task_struct *p, u64 dsq_id,
diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h
index b1c2a0dde76e..522c90d0ced2 100644
--- a/tools/sched_ext/include/scx/common.bpf.h
+++ b/tools/sched_ext/include/scx/common.bpf.h
@@ -62,8 +62,7 @@ s32 scx_bpf_create_dsq(u64 dsq_id, s32 node) __ksym;
s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, bool *is_idle) __ksym;
s32 __scx_bpf_select_cpu_and(struct task_struct *p, const struct cpumask *cpus_allowed,
struct scx_bpf_select_cpu_and_args *args) __ksym __weak;
-void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __ksym __weak;
-void __scx_bpf_dsq_insert_vtime(struct task_struct *p, struct scx_bpf_dsq_insert_vtime_args *args) __ksym __weak;
+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;
diff --git a/tools/sched_ext/include/scx/compat.bpf.h b/tools/sched_ext/include/scx/compat.bpf.h
index e172de696f99..33c26928f4e9 100644
--- a/tools/sched_ext/include/scx/compat.bpf.h
+++ b/tools/sched_ext/include/scx/compat.bpf.h
@@ -196,7 +196,7 @@ scx_bpf_select_cpu_and(struct task_struct *p, s32 prev_cpu, u64 wake_flags,
* Inline wrapper that packs scalar arguments into a struct and calls
* __scx_bpf_dsq_insert_vtime(). See __scx_bpf_dsq_insert_vtime() for details.
*/
-static inline void
+static inline bool
scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime,
u64 enq_flags)
{
@@ -208,10 +208,29 @@ scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime
.enq_flags = enq_flags,
};
- __scx_bpf_dsq_insert_vtime(p, &args);
+ return __scx_bpf_dsq_insert_vtime(p, &args);
} else {
scx_bpf_dsq_insert_vtime___compat(p, dsq_id, slice, vtime,
enq_flags);
+ return true;
+ }
+}
+
+/*
+ * 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;
+
+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);
+ } else {
+ scx_bpf_dsq_insert___compat(p, dsq_id, slice, enq_flags);
+ return true;
}
}
--
2.51.0
Powered by blists - more mailing lists