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sched_ext: Move scx_error() out of scx_link_sched()'s lock region

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scx_link_sched() holds scx_sched_lock. The scx_error() calls inside take the
same lock through scx_claim_exit() and deadlock. Move them out of the guard.

Fixes: 6b4576b097 ("sched_ext: Reject sub-sched attachment to a disabled parent")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2026-05-07 11:05:31 -10:00
parent b34c82777a
commit 4616a9c36b
1 changed files with 17 additions and 5 deletions
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22
kernel/sched/ext.c
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@ -5585,10 +5585,12 @@ static void refresh_watchdog(void)
static s32 scx_link_sched(struct scx_sched *sch)
{
const char *err_msg;
s32 ret = 0;
scoped_guard(raw_spinlock_irq, &scx_sched_lock) {
#ifdef CONFIG_EXT_SUB_SCHED
struct scx_sched *parent = scx_parent(sch);
s32 ret;
if (parent) {
/*
@ -5598,15 +5600,16 @@ static s32 scx_link_sched(struct scx_sched *sch)
* parent can shoot us down.
*/
if (atomic_read(&parent->exit_kind) != SCX_EXIT_NONE) {
scx_error(sch, "parent disabled");
return -ENOENT;
err_msg = "parent disabled";
ret = -ENOENT;
break;
}
ret = rhashtable_lookup_insert_fast(&scx_sched_hash,
&sch->hash_node, scx_sched_hash_params);
if (ret) {
scx_error(sch, "failed to insert into scx_sched_hash (%d)", ret);
return ret;
err_msg = "failed to insert into scx_sched_hash";
break;
}
list_add_tail(&sch->sibling, &parent->children);
@ -5616,6 +5619,15 @@ static 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;
}