commit e06ece82d7b0 ("sched_ext: Report NMI kicks with scx_error()") made
scx_bpf_kick_cpu() reject NMI calls, and its cover letter describes the
reachability: sched_ext kfuncs in the "any" category "are callable from
tracing progs that can attach to functions running in NMI", and an unlucky
call from there "could deadlock the machine". The fix in that series made
the error/exit path lock-free so scx_error() is safe to call from NMI. That
closes the *error* path of every kfunc, but not a kfunc's own
business-logic lock acquisition on its success path.

The remaining lock-taking kfuncs that scx_kfunc_context_filter() exposes to
BPF_PROG_TYPE_TRACING have the same hazard: if an NMI lands on a CPU whose
interrupted context already holds the lock, the kfunc's raw spinlock
acquisition spins forever and hard-locks the CPU:

 - scx_bpf_destroy_dsq()                    -> dsq->lock
 - scx_bpf_dsq_reenq()                      -> rq's deferred_reenq_lock
 - scx_bpf_cpuperf_set() / scx_bpf_cidperf_set() -> rq->lock
 - scx_bpf_sub_grant() / scx_bpf_sub_revoke()     -> pshard lock
   (via the shared sub_cap_preamble())
 - bpf_iter_scx_dsq_next() / bpf_iter_scx_dsq_destroy() -> dsq->lock
   (bpf_iter_scx_dsq_new() is lockless and needs no guard)

As things stand, there is no scenario for reenqueueing, iterating a DSQ,
setting a performance target or granting sub-caps from NMI. The guards
defend against a buggy or malicious BPF program turning an "any"-category
kfunc into a machine-wide hard-lockup through the door that
scx_kfunc_context_filter() already opens. This matches the intent of
scx_bpf_kick_cpu()'s NMI check, which the commit cited above added not to
enable an NMI use case but to surface such a bug as a clean abort.

Route all of them through a new scx_kf_allowed_ctx() helper and reuse
scx_bpf_kick_cpu()'s existing in_nmi() check - now shared with its cid
equivalent scx_bpf_kick_cid() through scx_kick_cpu() - so the rule is
stated once and the coverage is auditable from one place. scx_error() is
already NMI-safe (commit f883dbb64ca5 ("sched_ext: Make exit claiming
lock-free")), so the reject-abort cannot deadlock the lock acquisition.
Kfuncs with an error return report -EDEADLK, the situation being avoided.

Read-only members of the reachable sets (dsq_peek, dsq_nr_queued,
cpuperf_cur/cap, sub_caps, the idle cpumask helpers and the cid lookups)
take no scheduler lock on the path a tracing program reaches them, and were
audited to that effect; they are correctly left unguarded. The select_cpu
kfuncs do take pi_lock, but scx_kfunc_context_filter() only exposes the
any/idle/cid sets to BPF_PROG_TYPE_TRACING, and struct_ops run in task
context, so no lock-taking path here is reachable from NMI.

Link: https://lore.kernel.org/r/20260901095652.1009104-1-liwanwu@kylinos.cn
Acked-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Wanwu Li <liwanwu@kylinos.cn>
---
Changes in v2:
- Rename the helper to scx_kf_allowed_ctx(), implemented as a macro that
  passes __func__ to the inline __scx_kf_allowed_ctx() so callers no longer
  spell out @who (Tejun Heo).
- Report -EDEADLK instead of -EBUSY where a kfunc bails out with an error
  (Tejun Heo).
- Condense the in-code comment to the suggested wording (Tejun Heo); the
  extended rationale now lives in this commit message.
- Move the destroy_dsq() guard into the scx_bpf_destroy_dsq() kfunc itself
  so that __func__ reports the user-visible name and the internal callers
  of destroy_dsq() are unaffected. scx_kick_cpu() now reports itself in the
  error message (shared with scx_bpf_kick_cid()).
- Carry over Acked-by from Andrea Righi (v1).

 kernel/sched/ext/ext.c      | 33 ++++++++++++++++++++++++---------
 kernel/sched/ext/internal.h | 17 +++++++++++++++++
 kernel/sched/ext/sub.c      |  3 +++
 3 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index 10af28a9f2c0..09ce239e9c4b 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -9518,14 +9518,8 @@ void scx_kick_cpu(struct scx_sched *sch, s32 cpu, u64 flags)
 	struct rq *this_rq;
 	unsigned long irq_flags;
 
-	/*
-	 * The per-cpu kick list is guarded only by local_irq_save(), which does
-	 * not mask NMIs, so kicking from NMI could corrupt it and is unsupported.
-	 */
-	if (unlikely(in_nmi())) {
-		scx_error(sch, "scx_bpf_kick_cpu() called from NMI");
+	if (!scx_kf_allowed_ctx(sch))
 		return;
-	}
 
 	local_irq_save(irq_flags);
 
@@ -9693,8 +9687,13 @@ __bpf_kfunc void scx_bpf_destroy_dsq(u64 dsq_id, const struct bpf_prog_aux *aux)
 
 	guard(rcu)();
 	sch = scx_prog_sched(aux);
-	if (sch)
-		destroy_dsq(sch, dsq_id);
+	if (!sch)
+		return;
+
+	if (!scx_kf_allowed_ctx(sch))
+		return;
+
+	destroy_dsq(sch, dsq_id);
 }
 
 /**
@@ -9756,6 +9755,9 @@ __bpf_kfunc struct task_struct *bpf_iter_scx_dsq_next(struct bpf_iter_scx_dsq *i
 	if (!kit->dsq)
 		return NULL;
 
+	if (!scx_kf_allowed_ctx(kit->dsq->sched))
+		return NULL;
+
 	guard(raw_spinlock_irqsave)(&kit->dsq->lock);
 
 	return nldsq_cursor_next_task(&kit->cursor, kit->dsq);
@@ -9777,6 +9779,9 @@ __bpf_kfunc void bpf_iter_scx_dsq_destroy(struct bpf_iter_scx_dsq *it)
 	if (!list_empty(&kit->cursor.node)) {
 		unsigned long flags;
 
+		if (!scx_kf_allowed_ctx(kit->dsq->sched))
+			return;
+
 		raw_spin_lock_irqsave(&kit->dsq->lock, flags);
 		list_del_init(&kit->cursor.node);
 		raw_spin_unlock_irqrestore(&kit->dsq->lock, flags);
@@ -9857,6 +9862,9 @@ __bpf_kfunc void scx_bpf_dsq_reenq(u64 dsq_id, u64 reenq_flags,
 		return;
 	}
 
+	if (!scx_kf_allowed_ctx(sch))
+		return;
+
 	/* not specifying any filter bits is the same as %SCX_REENQ_ANY */
 	if (!(reenq_flags & __SCX_REENQ_FILTER_MASK))
 		reenq_flags |= SCX_REENQ_ANY;
@@ -10244,6 +10252,9 @@ __bpf_kfunc void scx_bpf_cpuperf_set(s32 cpu, u32 perf, const struct bpf_prog_au
 	if (unlikely(!sch))
 		return;
 
+	if (!scx_kf_allowed_ctx(sch))
+		return;
+
 	scx_cpuperf_set(sch, cpu, perf);
 }
 
@@ -10269,6 +10280,10 @@ __bpf_kfunc s32 scx_bpf_cidperf_set(s32 cid, u32 perf,
 	sch = scx_prog_sched(aux);
 	if (unlikely(!sch))
 		return -ENODEV;
+
+	if (!scx_kf_allowed_ctx(sch))
+		return -EDEADLK;
+
 	cpu = scx_cid_to_cpu(sch, cid);
 	if (cpu < 0)
 		return cpu;
diff --git a/kernel/sched/ext/internal.h b/kernel/sched/ext/internal.h
index 27bbf5e04d90..d7f48ec63e01 100644
--- a/kernel/sched/ext/internal.h
+++ b/kernel/sched/ext/internal.h
@@ -2091,6 +2091,23 @@ extern struct scx_sched *scx_enabling_sub_sched;
 #define scx_error(sch, fmt, args...)						\
 	scx_exit((sch), SCX_EXIT_ERROR, 0, fmt, ##args)
 
+/*
+ * Tracing progs can call kfuncs from NMI. Kfuncs that take scheduler locks or
+ * touch the kick lists, which are only protected by irq masking, can't run
+ * there, so abort the scheduler instead. scx_error() is NMI-safe.
+ */
+static __always_inline bool __scx_kf_allowed_ctx(struct scx_sched *sch,
+						 const char *who)
+{
+	if (unlikely(in_nmi())) {
+		scx_error(sch, "%s called from NMI", who);
+		return false;
+	}
+	return true;
+}
+
+#define scx_kf_allowed_ctx(sch) __scx_kf_allowed_ctx((sch), __func__)
+
 /**
  * scx_root_protected_live - Root sched for paths that only run while live
  *
diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c
index 0554448835bd..7d444f7aa7ab 100644
--- a/kernel/sched/ext/sub.c
+++ b/kernel/sched/ext/sub.c
@@ -2265,6 +2265,9 @@ static s32 sub_cap_preamble(u64 cgroup_id, u64 caps, const struct bpf_prog_aux *
 	if (unlikely(!parent))
 		return -ENODEV;
 
+	if (!__scx_kf_allowed_ctx(parent, "sub-cap kfuncs"))
+		return -EDEADLK;
+
 	if (!scx_is_cid_type()) {
 		scx_error(parent, "sub-cap kfuncs require a cid-form scheduler");
 		return -EOPNOTSUPP;
-- 
2.25.1

Hello,

On Wed, Sep 02, 2026 at 10:31:24AM +0800, Wanwu Li wrote:
> -	if (sch)
> -		destroy_dsq(sch, dsq_id);
> +	if (!sch)
> +		return;

unlikely(!sch) like the other kfuncs.

> @@ -9756,6 +9755,9 @@ __bpf_kfunc struct task_struct *bpf_iter_scx_dsq_next(struct bpf_iter_scx_dsq *i
>  	if (!kit->dsq)
>  		return NULL;
>
> +	if (!scx_kf_allowed_ctx(kit->dsq->sched))
> +		return NULL;

new(), next() and destroy() always run in the same context, so reject in
bpf_iter_scx_dsq_new() and drop the checks from next() and destroy(). With
kit->dsq left NULL, both are no-ops.

> +static __always_inline bool __scx_kf_allowed_ctx(struct scx_sched *sch,
> +						 const char *who)

No need to wrap.

Thanks.

-- 
tejun

Hi Tejun,

Thanks for the review. v3 folds in your three points (single
scx_kf_allowed_ctx() macro with no wrapper, one reject in
bpf_iter_scx_dsq_new(), unlikely(!sch) in scx_bpf_destroy_dsq()).

Continuing the audit that the sashiko bot kicked off, I swept every
kfunc exposed to BPF_PROG_TYPE_TRACING through the any / idle / cid
context-filter sets. I found a second class of problems beyond the
lock-taking set already covered. The first subclass I plan to fold
into v4 and want to make sure you agree with the scope.

Three "any"-category kfuncs read scx_locked_rq() on their success path
and treat a non-NULL return as "the rq lock is already held by me",
which a false positive under NMI turns into either a data race or a
wrong result:

  - scx_bpf_task_set_slice() (the sashiko bot's finding) races its
    direct p->scx.slice write with update_curr_scx()'s RMW of the same
    field.
  - scx_bpf_dsq_nr_queued() resolves %SCX_DSQ_LOCAL to
    (scx_locked_rq() ?: this_rq()) and can therefore report the wrong
    rq's length.
  - scx_bpf_locked_rq() hands the interrupted context's rq to the BPF
    program, which may then operate on it as if the lock were owned.

A second, different subclass I have NOT folded in, and would like your
guidance on.

scx_bpf_pick_idle_cpu_node() and scx_bpf_pick_any_cpu_node() pass the
caller's @node and @flags straight through to scx_pick_idle_cpu(). When
@node != NUMA_NO_NODE and SCX_PICK_IDLE_IN_NODE is not set and no idle
CPU is found in the starting node, the search falls through to
pick_idle_cpu_from_online_nodes() (kernel/sched/ext/idle.c:151), which
writes the per-CPU nodemask per_cpu_unvisited (idle.c:146) under only
preempt_disable(). preempt_disable() does not mask NMIs, so an NMI that
lands on a CPU whose interrupted context is mid-way through that loop
clobbers the scratch nodemask the interrupted context is still
iterating. Same "irq/preempt-only per-CPU state is not NMI-safe" premise
behind scx_kick_cpu()'s check, just a scratch buffer rather than a
lock or a list.

Note this is a wrong-result / lost-scratch race for the interrupted
struct_ops context, not a hard lockup, and it needs CONFIG_NUMA plus
per-node idle tracking to be reachable. The non-node
scx_bpf_pick_idle_cpu()/pick_any_cpu() force NUMA_NO_NODE and never
reach the scratch, and every cid-set kfunc is an RCU-read lookup, so the
hazard is confined to those two node-variants.

Should these two issue classes be folded into this series or are they 
out of scope for now? Looking forward to your suggestion.

Thanks,
Wanwu

在 2026/9/2 14:44, Tejun Heo 写道:
> Hello,
> 
> On Wed, Sep 02, 2026 at 10:31:24AM +0800, Wanwu Li wrote:
>> -	if (sch)
>> -		destroy_dsq(sch, dsq_id);
>> +	if (!sch)
>> +		return;
> 
> unlikely(!sch) like the other kfuncs.
> 
>> @@ -9756,6 +9755,9 @@ __bpf_kfunc struct task_struct *bpf_iter_scx_dsq_next(struct bpf_iter_scx_dsq *i
>>   	if (!kit->dsq)
>>   		return NULL;
>>
>> +	if (!scx_kf_allowed_ctx(kit->dsq->sched))
>> +		return NULL;
> 
> new(), next() and destroy() always run in the same context, so reject in
> bpf_iter_scx_dsq_new() and drop the checks from next() and destroy(). With
> kit->dsq left NULL, both are no-ops.
> 
>> +static __always_inline bool __scx_kf_allowed_ctx(struct scx_sched *sch,
>> +						 const char *who)
> 
> No need to wrap.
> 
> Thanks.
> 

Hello,

On Wed, Sep 02, 2026 at 09:48:28PM +0800, liwanwu wrote:
> Three "any"-category kfuncs read scx_locked_rq() on their success path
> and treat a non-NULL return as "the rq lock is already held by me",
> which a false positive under NMI turns into either a data race or a
> wrong result:

Let's add the in_nmi() test to scx_locked_rq() so that it returns NULL from
NMI. That sends all three down their unlocked paths.

> pick_idle_cpu_from_online_nodes() (kernel/sched/ext/idle.c:151), which
> writes the per-CPU nodemask per_cpu_unvisited (idle.c:146) under only
> preempt_disable(). preempt_disable() does not mask NMIs, so an NMI that
> lands on a CPU whose interrupted context is mid-way through that loop
> clobbers the scratch nodemask the interrupted context is still
> iterating.

That probably needs to be irqsave'd. preempt_disable() doesn't mask IRQs
either and the idle kfuncs can be called from IRQ-enabled contexts. As for
NMI, if someone is calling pick_idle from NMI, they're asking for it. As
long as the machine doesn't crash, it doesn't matter.

Thanks.

-- 
tejun

commit e06ece82d7b0 ("sched_ext: Report NMI kicks with scx_error()") made
scx_bpf_kick_cpu() reject NMI calls, and its cover letter describes the
reachability: sched_ext kfuncs in the "any" category "are callable from
tracing progs that can attach to functions running in NMI", and an unlucky
call from there "could deadlock the machine". The fix in that series made
the error/exit path lock-free so scx_error() is safe to call from NMI. That
closes the *error* path of every kfunc, but not a kfunc's own
business-logic lock acquisition on its success path.

The remaining lock-taking kfuncs that scx_kfunc_context_filter() exposes to
BPF_PROG_TYPE_TRACING have the same hazard: if an NMI lands on a CPU whose
interrupted context already holds the lock, the kfunc's raw spinlock
acquisition spins forever and hard-locks the CPU:

 - scx_bpf_destroy_dsq()                    -> dsq->lock
 - scx_bpf_dsq_reenq()                      -> rq's deferred_reenq_lock
 - scx_bpf_cpuperf_set() / scx_bpf_cidperf_set() -> rq->lock
 - scx_bpf_sub_grant() / scx_bpf_sub_revoke()     -> pshard lock
   (via the shared sub_cap_preamble())
 - bpf_iter_scx_dsq_next() / bpf_iter_scx_dsq_destroy() -> dsq->lock
   (the reject is placed in bpf_iter_scx_dsq_new(), which is otherwise
    lockless, so next() and destroy() are no-ops while it leaves kit->dsq
    NULL)

As things stand, there is no scenario for reenqueueing, iterating a DSQ,
setting a performance target or granting sub-caps from NMI. The guards
defend against a buggy or malicious BPF program turning an "any"-category
kfunc into a machine-wide hard-lockup through the door that
scx_kfunc_context_filter() already opens. This matches the intent of
scx_bpf_kick_cpu()'s NMI check, which the commit cited above added not to
enable an NMI use case but to surface such a bug as a clean abort.

Route all of them through a new scx_kf_allowed_ctx() helper and reuse
scx_bpf_kick_cpu()'s existing in_nmi() check - now shared with its cid
equivalent scx_bpf_kick_cid() through scx_kick_cpu() - so the rule is
stated once and the coverage is auditable from one place. scx_error() is
already NMI-safe (commit f883dbb64ca5 ("sched_ext: Make exit claiming
lock-free")), so the reject-abort cannot deadlock the lock acquisition.
Kfuncs with an error return report -EDEADLK, the situation being avoided.

Read-only members of the reachable sets (dsq_peek, dsq_nr_queued,
cpuperf_cur/cap, sub_caps, the idle cpumask helpers and the cid lookups)
take no scheduler lock on the path a tracing program reaches them, and were
audited to that effect; they are correctly left unguarded. The select_cpu
kfuncs do take pi_lock, but scx_kfunc_context_filter() only exposes the
any/idle/cid sets to BPF_PROG_TYPE_TRACING, and struct_ops run in task
context, so no lock-taking path here is reachable from NMI.

Link: https://lore.kernel.org/r/20260901095652.1009104-1-liwanwu@kylinos.cn
Acked-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Wanwu Li <liwanwu@kylinos.cn>
---
V2 -> V3:
 - Collapse the __scx_kf_allowed_ctx() inline + scx_kf_allowed_ctx() macro
   into a single macro that takes the function name implicitly (Tejun Heo).
 - Guard DSQ iteration once in bpf_iter_scx_dsq_new(); drop the redundant
   checks in bpf_iter_scx_dsq_next()/destroy() (Tejun Heo).
 - Use unlikely(!sch) in scx_bpf_destroy_dsq() (Tejun Heo).

v2: https://lore.kernel.org/r/20260902023124.1422942-1-liwanwu@kylinos.cn
v1: https://lore.kernel.org/r/20260901095652.1009104-1-liwanwu@kylinos.cn

 kernel/sched/ext/ext.c      | 30 +++++++++++++++++++++---------
 kernel/sched/ext/internal.h | 16 ++++++++++++++++
 kernel/sched/ext/sub.c      |  3 +++
 3 files changed, 40 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index 10af28a9f2c0..3f8bde1dbb4c 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -9518,14 +9518,8 @@ void scx_kick_cpu(struct scx_sched *sch, s32 cpu, u64 flags)
 	struct rq *this_rq;
 	unsigned long irq_flags;
 
-	/*
-	 * The per-cpu kick list is guarded only by local_irq_save(), which does
-	 * not mask NMIs, so kicking from NMI could corrupt it and is unsupported.
-	 */
-	if (unlikely(in_nmi())) {
-		scx_error(sch, "scx_bpf_kick_cpu() called from NMI");
+	if (!scx_kf_allowed_ctx(sch))
 		return;
-	}
 
 	local_irq_save(irq_flags);
 
@@ -9693,8 +9687,13 @@ __bpf_kfunc void scx_bpf_destroy_dsq(u64 dsq_id, const struct bpf_prog_aux *aux)
 
 	guard(rcu)();
 	sch = scx_prog_sched(aux);
-	if (sch)
-		destroy_dsq(sch, dsq_id);
+	if (unlikely(!sch))
+		return;
+
+	if (!scx_kf_allowed_ctx(sch))
+		return;
+
+	destroy_dsq(sch, dsq_id);
 }
 
 /**
@@ -9731,6 +9730,9 @@ __bpf_kfunc int bpf_iter_scx_dsq_new(struct bpf_iter_scx_dsq *it, u64 dsq_id,
 	if (unlikely(!sch))
 		return -ENODEV;
 
+	if (!scx_kf_allowed_ctx(sch))
+		return -EDEADLK;
+
 	if (flags & ~__SCX_DSQ_ITER_USER_FLAGS)
 		return -EINVAL;
 
@@ -9857,6 +9859,9 @@ __bpf_kfunc void scx_bpf_dsq_reenq(u64 dsq_id, u64 reenq_flags,
 		return;
 	}
 
+	if (!scx_kf_allowed_ctx(sch))
+		return;
+
 	/* not specifying any filter bits is the same as %SCX_REENQ_ANY */
 	if (!(reenq_flags & __SCX_REENQ_FILTER_MASK))
 		reenq_flags |= SCX_REENQ_ANY;
@@ -10244,6 +10249,9 @@ __bpf_kfunc void scx_bpf_cpuperf_set(s32 cpu, u32 perf, const struct bpf_prog_au
 	if (unlikely(!sch))
 		return;
 
+	if (!scx_kf_allowed_ctx(sch))
+		return;
+
 	scx_cpuperf_set(sch, cpu, perf);
 }
 
@@ -10269,6 +10277,10 @@ __bpf_kfunc s32 scx_bpf_cidperf_set(s32 cid, u32 perf,
 	sch = scx_prog_sched(aux);
 	if (unlikely(!sch))
 		return -ENODEV;
+
+	if (!scx_kf_allowed_ctx(sch))
+		return -EDEADLK;
+
 	cpu = scx_cid_to_cpu(sch, cid);
 	if (cpu < 0)
 		return cpu;
diff --git a/kernel/sched/ext/internal.h b/kernel/sched/ext/internal.h
index 27bbf5e04d90..ca8ebb11f03c 100644
--- a/kernel/sched/ext/internal.h
+++ b/kernel/sched/ext/internal.h
@@ -2091,6 +2091,22 @@ extern struct scx_sched *scx_enabling_sub_sched;
 #define scx_error(sch, fmt, args...)						\
 	scx_exit((sch), SCX_EXIT_ERROR, 0, fmt, ##args)
 
+/*
+ * Tracing progs can call kfuncs from NMI. Kfuncs that take scheduler locks or
+ * touch the kick lists, which are only protected by irq masking, can't run
+ * there, so abort the scheduler instead. scx_error() is NMI-safe.
+ */
+#define scx_kf_allowed_ctx(sch)						\
+({										\
+	bool __allowed = true;							\
+										\
+	if (unlikely(in_nmi())) {						\
+		scx_error((sch), "%s called from NMI", __func__);		\
+		__allowed = false;						\
+	}									\
+	__allowed;								\
+})
+
 /**
  * scx_root_protected_live - Root sched for paths that only run while live
  *
diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c
index 0554448835bd..78349acd0a67 100644
--- a/kernel/sched/ext/sub.c
+++ b/kernel/sched/ext/sub.c
@@ -2265,6 +2265,9 @@ static s32 sub_cap_preamble(u64 cgroup_id, u64 caps, const struct bpf_prog_aux *
 	if (unlikely(!parent))
 		return -ENODEV;
 
+	if (!scx_kf_allowed_ctx(parent))
+		return -EDEADLK;
+
 	if (!scx_is_cid_type()) {
 		scx_error(parent, "sub-cap kfuncs require a cid-form scheduler");
 		return -EOPNOTSUPP;
-- 
2.25.1

Hello,

On Wed, Sep 02, 2026 at 05:36:11PM +0800, Wanwu Li wrote:
> +#define scx_kf_allowed_ctx(sch)						\
> +({										\
> +	bool __allowed = true;							\

Applied to sched_ext/for-7.4 with the following changes:

- "No need to wrap" in my v2 reply was about the line wrap of the function
  signature. Restored the inline function + macro wrapper form:

    static __always_inline bool __scx_kf_allowed_ctx(struct scx_sched *sch, const char *who)
    {
    	if (unlikely(in_nmi())) {
    		scx_error(sch, "%s called from NMI", who);
    		return false;
    	}
    	return true;
    }

    #define scx_kf_allowed_ctx(sch)	__scx_kf_allowed_ctx((sch), __func__)

- struct_ops don't run in task context (e.g. ops.tick() runs from the tick
  interrupt). They just never run in NMI. Updated the last paragraph of the
  description accordingly.

Thanks.

--
tejun

Thanks for the correction and the guidance. I'll send a follow-up
patch to fix the remaining issues.

在 2026/9/3 07:05, Tejun Heo 写道:
> Hello,
> 
> On Wed, Sep 02, 2026 at 05:36:11PM +0800, Wanwu Li wrote:
>> +#define scx_kf_allowed_ctx(sch)						\
>> +({										\
>> +	bool __allowed = true;							\
> 
> Applied to sched_ext/for-7.4 with the following changes:
> 
> - "No need to wrap" in my v2 reply was about the line wrap of the function
>    signature. Restored the inline function + macro wrapper form:
> 
>      static __always_inline bool __scx_kf_allowed_ctx(struct scx_sched *sch, const char *who)
>      {
>      	if (unlikely(in_nmi())) {
>      		scx_error(sch, "%s called from NMI", who);
>      		return false;
>      	}
>      	return true;
>      }
> 
>      #define scx_kf_allowed_ctx(sch)	__scx_kf_allowed_ctx((sch), __func__)
> 
> - struct_ops don't run in task context (e.g. ops.tick() runs from the tick
>    interrupt). They just never run in NMI. Updated the last paragraph of the
>    description accordingly.
> 
> Thanks.
> 
> --
> tejun