Remove argument from open_softirq which is always NULL

As git-grep shows, open_softirq() is always called with the last argument
being NULL

block/blk-core.c:       open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
kernel/hrtimer.c:       open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL);
kernel/rcuclassic.c:    open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
kernel/rcupreempt.c:    open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
kernel/sched.c: open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);
kernel/softirq.c:       open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
kernel/softirq.c:       open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
kernel/timer.c: open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
net/core/dev.c: open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL);
net/core/dev.c: open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL);

This observation has already been made by Matthew Wilcox in June 2002
(http://www.cs.helsinki.fi/linux/linux-kernel/2002-25/0687.html)

"I notice that none of the current softirq routines use the data element
passed to them."

and the situation hasn't changed since them. So it appears we can safely
remove that extra argument to save 128 (54) bytes of kernel data (text).

Signed-off-by: Carlos R. Mafra <crmafra@ift.unesp.br>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

block/blk-core.c

@@ -2048,7 +2048,7 @@ int __init blk_dev_init(void)
 	for_each_possible_cpu(i)
 		INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
 
-	open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
+	open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
 	register_hotcpu_notifier(&blk_cpu_notifier);
 
 	return 0;

include/linux/interrupt.h

@@ -285,12 +285,11 @@ enum
 struct softirq_action
 {
 	void	(*action)(struct softirq_action *);
-	void	*data;
 };
 
 asmlinkage void do_softirq(void);
 asmlinkage void __do_softirq(void);
-extern void open_softirq(int nr, void (*action)(struct softirq_action*), void *data);
+extern void open_softirq(int nr, void (*action)(struct softirq_action *));
 extern void softirq_init(void);
 #define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0)
 extern void raise_softirq_irqoff(unsigned int nr);

kernel/hrtimer.c

@@ -1669,7 +1669,7 @@ void __init hrtimers_init(void)
 			  (void *)(long)smp_processor_id());
 	register_cpu_notifier(&hrtimers_nb);
 #ifdef CONFIG_HIGH_RES_TIMERS
-	open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL);
+	open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq);
 #endif
 }
 

kernel/rcuclassic.c

@@ -529,7 +529,7 @@ static void __cpuinit rcu_online_cpu(int cpu)
 
 	rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
 	rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
-	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
+	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 }
 
 static int __cpuinit rcu_cpu_notify(struct notifier_block *self,

kernel/rcupreempt.c

@@ -1125,7 +1125,7 @@ void __init __rcu_init(void)
 	for_each_online_cpu(cpu)
 		rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,	(void *)(long) cpu);
 
-	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
+	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 }
 
 /*

kernel/sched.c

@@ -8154,7 +8154,7 @@ void __init sched_init(void)
 #endif
 
 #ifdef CONFIG_SMP
-	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);
+	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
 #endif
 
 #ifdef CONFIG_RT_MUTEXES

kernel/softirq.c

@@ -347,9 +347,8 @@ void raise_softirq(unsigned int nr)
 	local_irq_restore(flags);
 }
 
-void open_softirq(int nr, void (*action)(struct softirq_action*), void *data)
+void open_softirq(int nr, void (*action)(struct softirq_action *))
 {
-	softirq_vec[nr].data = data;
 	softirq_vec[nr].action = action;
 }
 
@@ -503,8 +502,8 @@ void __init softirq_init(void)
 			&per_cpu(tasklet_hi_vec, cpu).head;
 	}
 
-	open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
-	open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
+	open_softirq(TASKLET_SOFTIRQ, tasklet_action);
+	open_softirq(HI_SOFTIRQ, tasklet_hi_action);
 }
 
 static int ksoftirqd(void * __bind_cpu)

kernel/timer.c

@@ -1502,7 +1502,7 @@ void __init init_timers(void)
 
 	BUG_ON(err == NOTIFY_BAD);
 	register_cpu_notifier(&timers_nb);
-	open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
+	open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
 }
 
 /**

net/core/dev.c

@@ -4563,8 +4563,8 @@ static int __init net_dev_init(void)
 
 	dev_boot_phase = 0;
 
-	open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL);
-	open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL);
+	open_softirq(NET_TX_SOFTIRQ, net_tx_action);
+	open_softirq(NET_RX_SOFTIRQ, net_rx_action);
 
 	hotcpu_notifier(dev_cpu_callback, 0);
 	dst_init();