softirq: Remove unused 'action' parameter from action callback

When soft interrupt actions are called, they are passed a pointer to the
struct softirq action which contains the action's function pointer.

This pointer isn't useful, as the action callback already knows what
function it is. And since each callback handles a specific soft interrupt,
the callback also knows which soft interrupt number is running.

No soft interrupt action callback actually uses this parameter, so remove
it from the function pointer signature. This clarifies that soft interrupt
actions are global routines and makes it slightly cheaper to call them.

Signed-off-by: Caleb Sander Mateos <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Jens Axboe <[e-mail]>
Link: https://lore.kernel.org/all/[e-mail]

block/blk-mq.c

···
 		rq->q->mq_ops->complete(rq);
 }
 
-static __latent_entropy void blk_done_softirq(struct softirq_action *h)
+static __latent_entropy void blk_done_softirq(void)
 {
 	blk_complete_reqs(this_cpu_ptr(&blk_cpu_done));
 }

include/linux/interrupt.h

···
 
 struct softirq_action
 {
-	void	(*action)(struct softirq_action *);
+	void	(*action)(void);
 };
 
 asmlinkage void do_softirq(void);
···
 }
 #endif
 
-extern void open_softirq(int nr, void (*action)(struct softirq_action *));
+extern void open_softirq(int nr, void (*action)(void));
 extern void softirq_init(void);
 extern void __raise_softirq_irqoff(unsigned int nr);
 

kernel/rcu/tiny.c

···
 }
 
 /* Invoke the RCU callbacks whose grace period has elapsed.  */
-static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
+static __latent_entropy void rcu_process_callbacks(void)
 {
 	struct rcu_head *next, *list;
 	unsigned long flags;

kernel/rcu/tree.c

···
 		queue_work_on(rdp->cpu, rcu_gp_wq, &rdp->strict_work);
 }
 
-static void rcu_core_si(struct softirq_action *h)
+static void rcu_core_si(void)
 {
 	rcu_core();
 }

kernel/sched/fair.c

···
  * - indirectly from a remote scheduler_tick() for NOHZ idle balancing
  *   through the SMP cross-call nohz_csd_func()
  */
-static __latent_entropy void sched_balance_softirq(struct softirq_action *h)
+static __latent_entropy void sched_balance_softirq(void)
 {
 	struct rq *this_rq = this_rq();
 	enum cpu_idle_type idle = this_rq->idle_balance;

kernel/softirq.c

···
 		kstat_incr_softirqs_this_cpu(vec_nr);
 
 		trace_softirq_entry(vec_nr);
-		h->action(h);
+		h->action();
 		trace_softirq_exit(vec_nr);
 		if (unlikely(prev_count != preempt_count())) {
 			pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
···
 	or_softirq_pending(1UL << nr);
 }
 
-void open_softirq(int nr, void (*action)(struct softirq_action *))
+void open_softirq(int nr, void (*action)(void))
 {
 	softirq_vec[nr].action = action;
 }
···
 	return false;
 }
 
-static void tasklet_action_common(struct softirq_action *a,
-				  struct tasklet_head *tl_head,
+static void tasklet_action_common(struct tasklet_head *tl_head,
 				  unsigned int softirq_nr)
 {
 	struct tasklet_struct *list;
···
 	}
 }
 
-static __latent_entropy void tasklet_action(struct softirq_action *a)
+static __latent_entropy void tasklet_action(void)
 {
 	workqueue_softirq_action(false);
-	tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
+	tasklet_action_common(this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
 }
 
-static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
+static __latent_entropy void tasklet_hi_action(void)
 {
 	workqueue_softirq_action(true);
-	tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
+	tasklet_action_common(this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
 }
 
 void tasklet_setup(struct tasklet_struct *t,

kernel/time/hrtimer.c

···
 	}
 }
 
-static __latent_entropy void hrtimer_run_softirq(struct softirq_action *h)
+static __latent_entropy void hrtimer_run_softirq(void)
 {
 	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
 	unsigned long flags;

kernel/time/timer.c

···
 /*
  * This function runs timers and the timer-tq in bottom half context.
  */
-static __latent_entropy void run_timer_softirq(struct softirq_action *h)
+static __latent_entropy void run_timer_softirq(void)
 {
 	run_timer_base(BASE_LOCAL);
 	if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {

lib/irq_poll.c

···
 }
 EXPORT_SYMBOL(irq_poll_complete);
 
-static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
+static void __latent_entropy irq_poll_softirq(void)
 {
 	struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);
 	int rearm = 0, budget = irq_poll_budget;

net/core/dev.c

···
 }
 EXPORT_SYMBOL(netif_rx);
 
-static __latent_entropy void net_tx_action(struct softirq_action *h)
+static __latent_entropy void net_tx_action(void)
 {
 	struct softnet_data *sd = this_cpu_ptr(&softnet_data);
 
···
 	return 0;
 }
 
-static __latent_entropy void net_rx_action(struct softirq_action *h)
+static __latent_entropy void net_rx_action(void)
 {
 	struct softnet_data *sd = this_cpu_ptr(&softnet_data);
 	unsigned long time_limit = jiffies +