Commit 4616a9c3 authored by Tejun Heo's avatar Tejun Heo
Browse files

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



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: 6b4576b0 ("sched_ext: Reject sub-sched attachment to a disabled parent")
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
parent b34c8277

kernel/sched/ext.c

+17 −5
Original line number Diff line number Diff line
@@ -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;

}