diff options
Diffstat (limited to 'lib/irq_poll.c')
| -rw-r--r-- | lib/irq_poll.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/lib/irq_poll.c b/lib/irq_poll.c new file mode 100644 index 000000000..2d5329a42 --- /dev/null +++ b/lib/irq_poll.c @@ -0,0 +1,219 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Functions related to interrupt-poll handling in the block layer. This + * is similar to NAPI for network devices. + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/bio.h> +#include <linux/interrupt.h> +#include <linux/cpu.h> +#include <linux/irq_poll.h> +#include <linux/delay.h> + +static unsigned int irq_poll_budget __read_mostly = 256; + +static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll); + +/** + * irq_poll_sched - Schedule a run of the iopoll handler + * @iop: The parent iopoll structure + * + * Description: + * Add this irq_poll structure to the pending poll list and trigger the + * raise of the blk iopoll softirq. + **/ +void irq_poll_sched(struct irq_poll *iop) +{ + unsigned long flags; + + if (test_bit(IRQ_POLL_F_DISABLE, &iop->state)) + return; + if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state)) + return; + + local_irq_save(flags); + list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll)); + raise_softirq_irqoff(IRQ_POLL_SOFTIRQ); + local_irq_restore(flags); +} +EXPORT_SYMBOL(irq_poll_sched); + +/** + * __irq_poll_complete - Mark this @iop as un-polled again + * @iop: The parent iopoll structure + * + * Description: + * See irq_poll_complete(). This function must be called with interrupts + * disabled. + **/ +static void __irq_poll_complete(struct irq_poll *iop) +{ + list_del(&iop->list); + smp_mb__before_atomic(); + clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state); +} + +/** + * irq_poll_complete - Mark this @iop as un-polled again + * @iop: The parent iopoll structure + * + * Description: + * If a driver consumes less than the assigned budget in its run of the + * iopoll handler, it'll end the polled mode by calling this function. The + * iopoll handler will not be invoked again before irq_poll_sched() + * is called. + **/ +void irq_poll_complete(struct irq_poll *iop) +{ + unsigned long flags; + + local_irq_save(flags); + __irq_poll_complete(iop); + local_irq_restore(flags); +} +EXPORT_SYMBOL(irq_poll_complete); + +static void __latent_entropy irq_poll_softirq(struct softirq_action *h) +{ + struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll); + int rearm = 0, budget = irq_poll_budget; + unsigned long start_time = jiffies; + + local_irq_disable(); + + while (!list_empty(list)) { + struct irq_poll *iop; + int work, weight; + + /* + * If softirq window is exhausted then punt. + */ + if (budget <= 0 || time_after(jiffies, start_time)) { + rearm = 1; + break; + } + + local_irq_enable(); + + /* Even though interrupts have been re-enabled, this + * access is safe because interrupts can only add new + * entries to the tail of this list, and only ->poll() + * calls can remove this head entry from the list. + */ + iop = list_entry(list->next, struct irq_poll, list); + + weight = iop->weight; + work = 0; + if (test_bit(IRQ_POLL_F_SCHED, &iop->state)) + work = iop->poll(iop, weight); + + budget -= work; + + local_irq_disable(); + + /* + * Drivers must not modify the iopoll state, if they + * consume their assigned weight (or more, some drivers can't + * easily just stop processing, they have to complete an + * entire mask of commands).In such cases this code + * still "owns" the iopoll instance and therefore can + * move the instance around on the list at-will. + */ + if (work >= weight) { + if (test_bit(IRQ_POLL_F_DISABLE, &iop->state)) + __irq_poll_complete(iop); + else + list_move_tail(&iop->list, list); + } + } + + if (rearm) + __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ); + + local_irq_enable(); +} + +/** + * irq_poll_disable - Disable iopoll on this @iop + * @iop: The parent iopoll structure + * + * Description: + * Disable io polling and wait for any pending callbacks to have completed. + **/ +void irq_poll_disable(struct irq_poll *iop) +{ + set_bit(IRQ_POLL_F_DISABLE, &iop->state); + while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state)) + msleep(1); + clear_bit(IRQ_POLL_F_DISABLE, &iop->state); +} +EXPORT_SYMBOL(irq_poll_disable); + +/** + * irq_poll_enable - Enable iopoll on this @iop + * @iop: The parent iopoll structure + * + * Description: + * Enable iopoll on this @iop. Note that the handler run will not be + * scheduled, it will only mark it as active. + **/ +void irq_poll_enable(struct irq_poll *iop) +{ + BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state)); + smp_mb__before_atomic(); + clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state); +} +EXPORT_SYMBOL(irq_poll_enable); + +/** + * irq_poll_init - Initialize this @iop + * @iop: The parent iopoll structure + * @weight: The default weight (or command completion budget) + * @poll_fn: The handler to invoke + * + * Description: + * Initialize and enable this irq_poll structure. + **/ +void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn) +{ + memset(iop, 0, sizeof(*iop)); + INIT_LIST_HEAD(&iop->list); + iop->weight = weight; + iop->poll = poll_fn; +} +EXPORT_SYMBOL(irq_poll_init); + +static int irq_poll_cpu_dead(unsigned int cpu) +{ + /* + * If a CPU goes away, splice its entries to the current CPU and + * set the POLL softirq bit. The local_bh_disable()/enable() pair + * ensures that it is handled. Otherwise the current CPU could + * reach idle with the POLL softirq pending. + */ + local_bh_disable(); + local_irq_disable(); + list_splice_init(&per_cpu(blk_cpu_iopoll, cpu), + this_cpu_ptr(&blk_cpu_iopoll)); + __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ); + local_irq_enable(); + local_bh_enable(); + + return 0; +} + +static __init int irq_poll_setup(void) +{ + int i; + + for_each_possible_cpu(i) + INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i)); + + open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq); + cpuhp_setup_state_nocalls(CPUHP_IRQ_POLL_DEAD, "irq_poll:dead", NULL, + irq_poll_cpu_dead); + return 0; +} +subsys_initcall(irq_poll_setup); |