generic-ipi: make struct call_function_data lockless

[mirror_ubuntu-hirsute-kernel.git] / kernel / smp.c

diff --git a/kernel/smp.c b/kernel/smp.c
index 8e218500ab14b7ff0a91810b5bc34abbd64e2a7b..fd47a256a24e4e95005203ebe117a4e47fd9b44c 100644 (file)
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -29,8 +29,7 @@ enum {
 
 struct call_function_data {
        struct call_single_data csd;
-       spinlock_t              lock;
-       unsigned int            refs;
+       atomic_t                refs;
        cpumask_var_t           cpumask;
 };
 
@@ -39,9 +38,7 @@ struct call_single_queue {
        spinlock_t              lock;
 };
 
-static DEFINE_PER_CPU(struct call_function_data, cfd_data) = {
-       .lock                   = __SPIN_LOCK_UNLOCKED(cfd_data.lock),
-};
+static DEFINE_PER_CPU(struct call_function_data, cfd_data);
 
 static int
 hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
@@ -196,25 +193,18 @@ void generic_smp_call_function_interrupt(void)
        list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
                int refs;
 
-               spin_lock(&data->lock);
-               if (!cpumask_test_cpu(cpu, data->cpumask)) {
-                       spin_unlock(&data->lock);
+               if (!cpumask_test_and_clear_cpu(cpu, data->cpumask))
                        continue;
-               }
-               cpumask_clear_cpu(cpu, data->cpumask);
-               spin_unlock(&data->lock);
 
                data->csd.func(data->csd.info);
 
-               spin_lock(&data->lock);
-               WARN_ON(data->refs == 0);
-               refs = --data->refs;
+               refs = atomic_dec_return(&data->refs);
+               WARN_ON(refs < 0);
                if (!refs) {
                        spin_lock(&call_function.lock);
                        list_del_rcu(&data->csd.list);
                        spin_unlock(&call_function.lock);
                }
-               spin_unlock(&data->lock);
 
                if (refs)
                        continue;
@@ -419,23 +409,20 @@ void smp_call_function_many(const struct cpumask *mask,
        data = &__get_cpu_var(cfd_data);
        csd_lock(&data->csd);
 
-       spin_lock_irqsave(&data->lock, flags);
        data->csd.func = func;
        data->csd.info = info;
        cpumask_and(data->cpumask, mask, cpu_online_mask);
        cpumask_clear_cpu(this_cpu, data->cpumask);
-       data->refs = cpumask_weight(data->cpumask);
+       atomic_set(&data->refs, cpumask_weight(data->cpumask));
 
-       spin_lock(&call_function.lock);
+       spin_lock_irqsave(&call_function.lock, flags);
        /*
         * Place entry at the _HEAD_ of the list, so that any cpu still
         * observing the entry in generic_smp_call_function_interrupt()
         * will not miss any other list entries:
         */
        list_add_rcu(&data->csd.list, &call_function.queue);
-       spin_unlock(&call_function.lock);
-
-       spin_unlock_irqrestore(&data->lock, flags);
+       spin_unlock_irqrestore(&call_function.lock, flags);
 
        /*
         * Make the list addition visible before sending the ipi.