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scheduler: rework load balancing locking

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Matheus
2026-08-17 21:47:00 -03:00
parent fc013c665c
commit d7343e7b55
1 changed files with 23 additions and 22 deletions
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kernel-src/sys/scheduler/queue.c
+23 -22
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@@ -303,34 +303,37 @@ void sched_load_balancer(context_t *, dpcarg_t) {
interrupt_set(false);
cpu_t *most_loaded = NULL;
cpu_t *least_loaded = NULL;
size_t most_loaded_count = 0;
size_t least_loaded_count = 0;
// find the least loaded and most loaded cpus
for (int i = 0; i < arch_smp_cpusawake; ++i) {
cpu_t *old_most_loaded = NULL;
cpu_t *old_least_loaded = NULL;
for (size_t i = 0; i < arch_smp_cpusawake; ++i) {
spinlock_acquire(&smp_cpus[i]->sched_lock);
if ((most_loaded == NULL || most_loaded->thread_count < smp_cpus[i]->thread_count) && smp_cpus[i]->stealable_thread_count) {
old_most_loaded = most_loaded;
size_t thread_count = smp_cpus[i]->thread_count;
size_t stealable_thread_count = smp_cpus[i]->stealable_thread_count;
spinlock_release(&smp_cpus[i]->sched_lock);
if ((most_loaded == NULL || most_loaded_count < thread_count) && stealable_thread_count) {
most_loaded = smp_cpus[i];
most_loaded_count = thread_count;
}
if (least_loaded == NULL || least_loaded->thread_count > smp_cpus[i]->thread_count) {
old_least_loaded = least_loaded;
if (least_loaded == NULL || least_loaded_count > thread_count) {
least_loaded = smp_cpus[i];
least_loaded_count = thread_count;
}
if (old_most_loaded)
spinlock_release(&old_most_loaded->sched_lock);
if (old_least_loaded && old_least_loaded != most_loaded && old_least_loaded != old_most_loaded)
spinlock_release(&old_least_loaded->sched_lock);
if (least_loaded != smp_cpus[i] && most_loaded != smp_cpus[i])
spinlock_release(&smp_cpus[i]->sched_lock);
}
if (most_loaded == NULL || most_loaded->thread_count <= 1 || most_loaded->thread_count == least_loaded->thread_count)
if (most_loaded == NULL || most_loaded == least_loaded)
return;
cpu_t *first = most_loaded->internal_id < least_loaded->internal_id ? most_loaded : least_loaded;
cpu_t *second = first == most_loaded ? least_loaded : most_loaded;
spinlock_acquire(&first->sched_lock);
spinlock_acquire(&second->sched_lock);
// the queues may have changed since the scan, so only move work if it still reduces the imbalance
if (most_loaded->stealable_thread_count == 0 || most_loaded->thread_count <= 1 || most_loaded->thread_count <= least_loaded->thread_count)
goto leave;
thread_t *thread = sched_steal_work_from_cpu(most_loaded);
@@ -342,8 +345,6 @@ void sched_load_balancer(context_t *, dpcarg_t) {
sched_preempt_cpu(least_loaded);
leave:
if (most_loaded)
spinlock_release(&most_loaded->sched_lock);
if (most_loaded != least_loaded)
spinlock_release(&least_loaded->sched_lock);
spinlock_release(&second->sched_lock);
spinlock_release(&first->sched_lock);
}