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sched_ext: Report scx_link_sched() failures inline

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scx_link_sched() carries each failure out of the locked section through
err_msg and ret because scx_error() used to take scx_sched_lock and couldn't
be called under it. That restriction is gone, so report each failure at the
site it's detected and return directly. The scx_error() here claims the exit
on the sched being linked, which has no descendants yet, and the locked
propagation walk is deferred, so nothing reacquires scx_sched_lock inline.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo
2026-07-27 11:20:32 -10:00
parent 3c4b380649
commit ee7aece608
1 changed files with 9 additions and 20 deletions
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kernel/sched/ext/ext.c
+9 -20
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@@ -5975,31 +5975,30 @@ static void refresh_watchdog(void)
s32 scx_link_sched(struct scx_sched *sch)
{
const char *err_msg = "";
s32 ret = 0;
scoped_guard(raw_spinlock_irqsave, &scx_bypass_lock) /* for the parent bypass check */
scoped_guard(raw_spinlock, &scx_sched_lock) {
#ifdef CONFIG_EXT_SUB_SCHED
struct scx_sched *parent = scx_parent(sch);
if (parent) {
s32 ret;
/*
* Bypass state is spread across per-cpu flags and a
* depth count, so inheriting it is tricky and has no
* valid use case. Refuse it.
*/
if (READ_ONCE(parent->bypass_depth)) {
err_msg = "parent bypassing";
ret = -EBUSY;
break;
scx_error(sch, "parent bypassing (%d)", -EBUSY);
return -EBUSY;
}
ret = rhashtable_lookup_insert_fast(&scx_sched_hash,
&sch->hash_node, scx_sched_hash_params);
if (ret) {
err_msg = "failed to insert into scx_sched_hash";
break;
scx_error(sch, "failed to insert into scx_sched_hash (%d)",
ret);
return ret;
}
list_add_tail_rcu(&sch->sibling, &parent->children);
@@ -6014,9 +6013,8 @@ s32 scx_link_sched(struct scx_sched *sch)
rhashtable_remove_fast(&scx_sched_hash, &sch->hash_node,
scx_sched_hash_params);
list_del_rcu(&sch->sibling);
err_msg = "parent disabled";
ret = -ENOENT;
break;
scx_error(sch, "parent disabled (%d)", -ENOENT);
return -ENOENT;
}
sch->linked = true;
@@ -6026,15 +6024,6 @@ s32 scx_link_sched(struct scx_sched *sch)
list_add_tail_rcu(&sch->all, &scx_sched_all);
}
/*
* scx_error() takes scx_sched_lock via scx_claim_exit(), so it must run after
* the guard above is released.
*/
if (ret) {
scx_error(sch, "%s (%d)", err_msg, ret);
return ret;
}
refresh_watchdog();
return 0;
}