On Thu, Aug 15, 2024 at 11:15:40AM -0600, 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.
>
> v2: use full 72 characters in commit description lines, add Reviewed-by
>
> Signed-off-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
> Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
For the RCU pieces:
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> ---
> 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(-)
>
> 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;
> --
> 2.45.2
>
