Commit 16b70698 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'sched_ext-for-6.16-rc1-fixes' of... 

Merge tag 'sched_ext-for-6.16-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:
 "Two fixes in the built-in idle selection helpers:

   - Fix prev_cpu handling to guarantee that idle selection never
     returns a CPU that's not allowed

   - Skip cross-node search when !NUMA which could lead to infinite
     looping due to a bug in NUMA iterator"

* tag 'sched_ext-for-6.16-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: idle: Skip cross-node search with !CONFIG_NUMA
  sched_ext: idle: Properly handle invalid prev_cpu during idle selection
parents 3719a04a 9960be72

kernel/sched/ext_idle.c

+19 −18
Original line number Diff line number Diff line
@@ -138,6 +138,7 @@ static s32 pick_idle_cpu_in_node(const struct cpumask *cpus_allowed, int node, u 
		goto retry;

}



#ifdef CONFIG_NUMA

/*

 * Tracks nodes that have not yet been visited when searching for an idle

 * CPU across all available nodes.
@@ -186,6 +187,13 @@ static s32 pick_idle_cpu_from_online_nodes(const struct cpumask *cpus_allowed, i 


	return cpu;

}

#else

static inline s32

pick_idle_cpu_from_online_nodes(const struct cpumask *cpus_allowed, int node, u64 flags)

{

	return -EBUSY;

}

#endif



/*

 * Find an idle CPU in the system, starting from @node.
@@ -447,10 +455,17 @@ s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, 
	const struct cpumask *llc_cpus = NULL, *numa_cpus = NULL;

	const struct cpumask *allowed = cpus_allowed ?: p->cpus_ptr;

	int node = scx_cpu_node_if_enabled(prev_cpu);

	bool is_prev_allowed;

	s32 cpu;



	preempt_disable();



	/*

	 * Check whether @prev_cpu is still within the allowed set. If not,

	 * we can still try selecting a nearby CPU.

	 */

	is_prev_allowed = cpumask_test_cpu(prev_cpu, allowed);



	/*

	 * Determine the subset of CPUs usable by @p within @cpus_allowed.

	 */
@@ -465,21 +480,6 @@ s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, 
			cpu = -EBUSY;

			goto out_enable;

		}



		/*

		 * If @prev_cpu is not in the allowed CPUs, skip topology

		 * optimizations and try to pick any idle CPU usable by the

		 * task.

		 *

		 * If %SCX_OPS_BUILTIN_IDLE_PER_NODE is enabled, prioritize

		 * the current node, as it may optimize some waker->wakee

		 * workloads.

		 */

		if (!cpumask_test_cpu(prev_cpu, allowed)) {

			node = scx_cpu_node_if_enabled(smp_processor_id());

			cpu = scx_pick_idle_cpu(allowed, node, flags);

			goto out_enable;

		}

	}



	/*
@@ -525,7 +525,7 @@ s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, 
		 * then avoid a migration.

		 */

		cpu = smp_processor_id();

		if (cpus_share_cache(cpu, prev_cpu) &&

		if (is_prev_allowed && cpus_share_cache(cpu, prev_cpu) &&

		    scx_idle_test_and_clear_cpu(prev_cpu)) {

			cpu = prev_cpu;

			goto out_unlock;
@@ -562,7 +562,8 @@ s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, 
		/*

		 * Keep using @prev_cpu if it's part of a fully idle core.

		 */

		if (cpumask_test_cpu(prev_cpu, idle_cpumask(node)->smt) &&

		if (is_prev_allowed &&

		    cpumask_test_cpu(prev_cpu, idle_cpumask(node)->smt) &&

		    scx_idle_test_and_clear_cpu(prev_cpu)) {

			cpu = prev_cpu;

			goto out_unlock;
@@ -611,7 +612,7 @@ s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, 
	/*

	 * Use @prev_cpu if it's idle.

	 */

	if (scx_idle_test_and_clear_cpu(prev_cpu)) {

	if (is_prev_allowed && scx_idle_test_and_clear_cpu(prev_cpu)) {

		cpu = prev_cpu;

		goto out_unlock;

	}