softirq: remove parameter from action callback

Commit Message

Caleb Sander Aug. 13, 2024, 11:31 p.m. UTC

When softirq actions are called, they are passed a pointer to the
entry in the softirq_vec table containing the action's function pointer.
This pointer isn't very useful, as the action callback already knows
what function it is. And since each callback handles a specific softirq,
the callback also knows which softirq number is running.

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

Signed-off-by: Caleb Sander Mateos <[e-mail]>
---
 block/blk-mq.c            |  2 +-
 include/linux/interrupt.h |  4 ++--
 kernel/rcu/tiny.c         |  2 +-
 kernel/rcu/tree.c         |  2 +-
 kernel/sched/fair.c       |  2 +-
 kernel/softirq.c          | 15 +++++++--------
 kernel/time/hrtimer.c     |  2 +-
 kernel/time/timer.c       |  2 +-
 lib/irq_poll.c            |  2 +-
 net/core/dev.c            |  4 ++--
 10 files changed, 18 insertions(+), 19 deletions(-)

Comments

Jens Axboe Aug. 14, 2024, 2 p.m. UTC | #1

On 8/13/24 5:31 PM, Caleb Sander Mateos wrote:
> When softirq actions are called, they are passed a pointer to the
> entry in the softirq_vec table containing the action's function pointer.
> This pointer isn't very useful, as the action callback already knows
> what function it is. And since each callback handles a specific softirq,
> the callback also knows which softirq number is running.
> 
> No softirq action callbacks actually use this parameter,
> so remove it from the function pointer signature.
> This clarifies that softirq actions are global routines
> and makes it slightly cheaper to call them.

Commit message should use ~72 char line lengths, but outside of that:

Reviewed-by: Jens Axboe <[e-mail]>

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e3c3c0c21b55..aa28157b1aaf 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1126,11 +1126,11 @@  static void blk_complete_reqs(struct llist_head *list)
 
 	llist_for_each_entry_safe(rq, next, entry, ipi_list)
 		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));
 }
 
 static int blk_softirq_cpu_dead(unsigned int cpu)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 3f30c88e0b4c..694de61e0b38 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -592,11 +592,11 @@  extern const char * const softirq_to_name[NR_SOFTIRQS];
  * asm/hardirq.h to get better cache usage.  KAO
  */
 
 struct softirq_action
 {
-	void	(*action)(struct softirq_action *);
+	void	(*action)(void);
 };
 
 asmlinkage void do_softirq(void);
 asmlinkage void __do_softirq(void);
 
@@ -607,11 +607,11 @@  static inline void do_softirq_post_smp_call_flush(unsigned int unused)
 {
 	do_softirq();
 }
 #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);
 
 extern void raise_softirq_irqoff(unsigned int nr);
 extern void raise_softirq(unsigned int nr);
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 4402d6f5f857..b3b3ce34df63 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -103,11 +103,11 @@  static inline bool rcu_reclaim_tiny(struct rcu_head *head)
 	rcu_lock_release(&rcu_callback_map);
 	return false;
 }
 
 /* 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;
 
 	/* Move the ready-to-invoke callbacks to a local list. */
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e641cc681901..93bd665637c0 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2853,11 +2853,11 @@  static __latent_entropy void rcu_core(void)
 	// If strict GPs, schedule an RCU reader in a clean environment.
 	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
 		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();
 }
 
 static void rcu_wake_cond(struct task_struct *t, int status)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9057584ec06d..8dc9385f6da4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12481,11 +12481,11 @@  static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
  * - directly from the local scheduler_tick() for periodic load balancing
  *
  * - 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;
 	/*
 	 * If this CPU has a pending NOHZ_BALANCE_KICK, then do the
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 02582017759a..d082e7840f88 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -549,11 +549,11 @@  static void handle_softirqs(bool ksirqd)
 		prev_count = preempt_count();
 
 		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",
 			       vec_nr, softirq_to_name[vec_nr], h->action,
 			       prev_count, preempt_count());
@@ -698,11 +698,11 @@  void __raise_softirq_irqoff(unsigned int nr)
 	lockdep_assert_irqs_disabled();
 	trace_softirq_raise(nr);
 	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;
 }
 
 /*
@@ -758,12 +758,11 @@  static bool tasklet_clear_sched(struct tasklet_struct *t)
 		  t->use_callback ? (void *)t->callback : (void *)t->func);
 
 	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;
 
 	local_irq_disable();
@@ -803,20 +802,20 @@  static void tasklet_action_common(struct softirq_action *a,
 		__raise_softirq_irqoff(softirq_nr);
 		local_irq_enable();
 	}
 }
 
-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,
 		   void (*callback)(struct tasklet_struct *))
 {
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index b8ee320208d4..836157e09e25 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1755,11 +1755,11 @@  static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
 				hrtimer_sync_wait_running(cpu_base, flags);
 		}
 	}
 }
 
-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;
 	ktime_t now;
 
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 64b0d8a0aa0f..760bbeb1f331 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -2438,11 +2438,11 @@  static void run_timer_base(int index)
 }
 
 /*
  * 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)) {
 		run_timer_base(BASE_GLOBAL);
 		run_timer_base(BASE_DEF);
diff --git a/lib/irq_poll.c b/lib/irq_poll.c
index 2d5329a42105..08b242bbdbdf 100644
--- a/lib/irq_poll.c
+++ b/lib/irq_poll.c
@@ -73,11 +73,11 @@  void irq_poll_complete(struct irq_poll *iop)
 	__irq_poll_complete(iop);
 	local_irq_restore(flags);
 }
 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;
 	unsigned long start_time = jiffies;
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 751d9b70e6ad..3ac02b0ca29e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5246,11 +5246,11 @@  int netif_rx(struct sk_buff *skb)
 		local_bh_enable();
 	return ret;
 }
 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);
 
 	if (sd->completion_queue) {
 		struct sk_buff *clist;
@@ -6919,11 +6919,11 @@  static int napi_threaded_poll(void *data)
 		napi_threaded_poll_loop(napi);
 
 	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 +
 		usecs_to_jiffies(READ_ONCE(net_hotdata.netdev_budget_usecs));
 	struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;