Merge tag 'sched_ext-for-6.18-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:
 "Five fixes addressing PREEMPT_RT compatibility and locking issues.

  Three commits fix potential deadlocks and sleeps in atomic contexts on
  RT kernels by converting locks to raw spinlocks and ensuring IRQ work
  runs in hard-irq context. The remaining two fix unsafe locking in the
  debug dump path and a variable dereference typo"

* tag 'sched_ext-for-6.18-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: Use IRQ_WORK_INIT_HARD() to initialize rq->scx.kick_cpus_irq_work
  sched_ext: Fix possible deadlock in the deferred_irq_workfn()
  sched/ext: convert scx_tasks_lock to raw spinlock
  sched_ext: Fix unsafe locking in the scx_dump_state()
  sched_ext: Fix use of uninitialized variable in scx_bpf_cpuperf_set()

Author: torvalds

kernel/sched/ext.c

@@ -25,7 +25,7 @@ static struct scx_sched __rcu *scx_root;
  * guarantee system safety. Maintain a dedicated task list which contains every
  * task between its fork and eventual free.
  */
-static DEFINE_SPINLOCK(scx_tasks_lock);
+static DEFINE_RAW_SPINLOCK(scx_tasks_lock);
 static LIST_HEAD(scx_tasks);
 
 /* ops enable/disable */
@@ -476,7 +476,7 @@ static void scx_task_iter_start(struct scx_task_iter *iter)
 	BUILD_BUG_ON(__SCX_DSQ_ITER_ALL_FLAGS &
 		     ((1U << __SCX_DSQ_LNODE_PRIV_SHIFT) - 1));
 
-	spin_lock_irq(&scx_tasks_lock);
+	raw_spin_lock_irq(&scx_tasks_lock);
 
 	iter->cursor = (struct sched_ext_entity){ .flags = SCX_TASK_CURSOR };
 	list_add(&iter->cursor.tasks_node, &scx_tasks);
@@ -507,14 +507,14 @@ static void scx_task_iter_unlock(struct scx_task_iter *iter)
 	__scx_task_iter_rq_unlock(iter);
 	if (iter->list_locked) {
 		iter->list_locked = false;
-		spin_unlock_irq(&scx_tasks_lock);
+		raw_spin_unlock_irq(&scx_tasks_lock);
 	}
 }
 
 static void __scx_task_iter_maybe_relock(struct scx_task_iter *iter)
 {
 	if (!iter->list_locked) {
-		spin_lock_irq(&scx_tasks_lock);
+		raw_spin_lock_irq(&scx_tasks_lock);
 		iter->list_locked = true;
 	}
 }
@@ -2940,9 +2940,9 @@ void scx_post_fork(struct task_struct *p)
 		}
 	}
 
-	spin_lock_irq(&scx_tasks_lock);
+	raw_spin_lock_irq(&scx_tasks_lock);
 	list_add_tail(&p->scx.tasks_node, &scx_tasks);
-	spin_unlock_irq(&scx_tasks_lock);
+	raw_spin_unlock_irq(&scx_tasks_lock);
 
 	percpu_up_read(&scx_fork_rwsem);
 }
@@ -2966,9 +2966,9 @@ void sched_ext_free(struct task_struct *p)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&scx_tasks_lock, flags);
+	raw_spin_lock_irqsave(&scx_tasks_lock, flags);
 	list_del_init(&p->scx.tasks_node);
-	spin_unlock_irqrestore(&scx_tasks_lock, flags);
+	raw_spin_unlock_irqrestore(&scx_tasks_lock, flags);
 
 	/*
 	 * @p is off scx_tasks and wholly ours. scx_enable()'s READY -> ENABLED
@@ -4276,7 +4276,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
 		size_t avail, used;
 		bool idle;
 
-		rq_lock(rq, &rf);
+		rq_lock_irqsave(rq, &rf);
 
 		idle = list_empty(&rq->scx.runnable_list) &&
 			rq->curr->sched_class == &idle_sched_class;
@@ -4345,7 +4345,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
 		list_for_each_entry(p, &rq->scx.runnable_list, scx.runnable_node)
 			scx_dump_task(&s, &dctx, p, ' ');
 	next:
-		rq_unlock(rq, &rf);
+		rq_unlock_irqrestore(rq, &rf);
 	}
 
 	dump_newline(&s);
@@ -5321,8 +5321,8 @@ void __init init_sched_ext_class(void)
 		BUG_ON(!zalloc_cpumask_var_node(&rq->scx.cpus_to_kick_if_idle, GFP_KERNEL, n));
 		BUG_ON(!zalloc_cpumask_var_node(&rq->scx.cpus_to_preempt, GFP_KERNEL, n));
 		BUG_ON(!zalloc_cpumask_var_node(&rq->scx.cpus_to_wait, GFP_KERNEL, n));
-		init_irq_work(&rq->scx.deferred_irq_work, deferred_irq_workfn);
-		init_irq_work(&rq->scx.kick_cpus_irq_work, kick_cpus_irq_workfn);
+		rq->scx.deferred_irq_work = IRQ_WORK_INIT_HARD(deferred_irq_workfn);
+		rq->scx.kick_cpus_irq_work = IRQ_WORK_INIT_HARD(kick_cpus_irq_workfn);
 
 		if (cpu_online(cpu))
 			cpu_rq(cpu)->scx.flags |= SCX_RQ_ONLINE;
@@ -6401,7 +6401,7 @@ __bpf_kfunc void scx_bpf_cpuperf_set(s32 cpu, u32 perf)
 
 	guard(rcu)();
 
-	sch = rcu_dereference(sch);
+	sch = rcu_dereference(scx_root);
 	if (unlikely(!sch))
 		return;