[PATCH] Remove More Unneccessary CPU Notifiers

From: Rusty Russell <rusty@rustcorp.com.au>

Three more removed CPU notifiers extracted from the hotplug CPU patch.

kernel/softirq.c: the tasklet cpu prepration callback is useless:
the vectors are already initialized to NULL.  Even with the hotplug
CPU patches, they're of little or no use.

fs/buffer.c: once again, they are already initialized to zero.

mm/page_alloc.c: once again, already initialized to zero.

fs/buffer.c

@@ -2987,33 +2987,6 @@ init_buffer_head(void *data, kmem_cache_t *cachep, unsigned long flags)
 	}
 }
 
-static void buffer_init_cpu(int cpu)
-{
-	struct bh_accounting *bha = &per_cpu(bh_accounting, cpu);
-	struct bh_lru *bhl = &per_cpu(bh_lrus, cpu);
-
-	bha->nr = 0;
-	bha->ratelimit = 0;
-	memset(bhl, 0, sizeof(*bhl));
-}
-	
-static int __devinit buffer_cpu_notify(struct notifier_block *self, 
-				unsigned long action, void *hcpu)
-{
-	long cpu = (long)hcpu;
-	switch(action) {
-	case CPU_UP_PREPARE:
-		buffer_init_cpu(cpu);
-		break;
-	default:
-		break;
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block __devinitdata buffer_nb = {
-	.notifier_call	= buffer_cpu_notify,
-};
 
 void __init buffer_init(void)
 {
@@ -3031,9 +3004,6 @@ void __init buffer_init(void)
 	 */
 	nrpages = (nr_free_buffer_pages() * 10) / 100;
 	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
-	buffer_cpu_notify(&buffer_nb, (unsigned long)CPU_UP_PREPARE,
-				(void *)(long)smp_processor_id());
-	register_cpu_notifier(&buffer_nb);
 }
 
 EXPORT_SYMBOL(__bforget);

kernel/softirq.c

@@ -300,38 +300,10 @@ void tasklet_kill(struct tasklet_struct *t)
 
 EXPORT_SYMBOL(tasklet_kill);
 
-static void tasklet_init_cpu(int cpu)
-{
-	per_cpu(tasklet_vec, cpu).list = NULL;
-	per_cpu(tasklet_hi_vec, cpu).list = NULL;
-}
-	
-static int tasklet_cpu_notify(struct notifier_block *self, 
-				unsigned long action, void *hcpu)
-{
-	long cpu = (long)hcpu;
-	switch(action) {
-	case CPU_UP_PREPARE:
-		tasklet_init_cpu(cpu);
-		break;
-	default:
-		break;
-	}
-	return 0;
-}
-
-static struct notifier_block tasklet_nb = {
-	.notifier_call	= tasklet_cpu_notify,
-	.next		= NULL,
-};
-
 void __init softirq_init(void)
 {
 	open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
 	open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
-	tasklet_cpu_notify(&tasklet_nb, (unsigned long)CPU_UP_PREPARE,
-				(void *)(long)smp_processor_id());
-	register_cpu_notifier(&tasklet_nb);
 }
 
 static int ksoftirqd(void * __bind_cpu)

mm/page_alloc.c

@@ -1536,34 +1536,9 @@ struct seq_operations vmstat_op = {
 
 #endif /* CONFIG_PROC_FS */
 
-static void __devinit init_page_alloc_cpu(int cpu)
-{
-	struct page_state *ps = &per_cpu(page_states, cpu);
-	memset(ps, 0, sizeof(*ps));
-}
-	
-static int __devinit page_alloc_cpu_notify(struct notifier_block *self, 
-				unsigned long action, void *hcpu)
-{
-	int cpu = (unsigned long)hcpu;
-	switch(action) {
-	case CPU_UP_PREPARE:
-		init_page_alloc_cpu(cpu);
-		break;
-	default:
-		break;
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block __devinitdata page_alloc_nb = {
-	.notifier_call	= page_alloc_cpu_notify,
-};
 
 void __init page_alloc_init(void)
 {
-	init_page_alloc_cpu(smp_processor_id());
-	register_cpu_notifier(&page_alloc_nb);
 }
 
 /*