diff options
| -rw-r--r-- | kernel/irq_work.c | 118 |
1 files changed, 106 insertions, 12 deletions
diff --git a/kernel/irq_work.c b/kernel/irq_work.c index e789beda8297..90b6b56f92e9 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -18,11 +18,36 @@ #include <linux/cpu.h> #include <linux/notifier.h> #include <linux/smp.h> +#include <linux/smpboot.h> #include <asm/processor.h> #include <linux/kasan.h> static DEFINE_PER_CPU(struct llist_head, raised_list); static DEFINE_PER_CPU(struct llist_head, lazy_list); +static DEFINE_PER_CPU(struct task_struct *, irq_workd); + +static void wake_irq_workd(void) +{ + struct task_struct *tsk = __this_cpu_read(irq_workd); + + if (!llist_empty(this_cpu_ptr(&lazy_list)) && tsk) + wake_up_process(tsk); +} + +#ifdef CONFIG_SMP +static void irq_work_wake(struct irq_work *entry) +{ + wake_irq_workd(); +} + +static DEFINE_PER_CPU(struct irq_work, irq_work_wakeup) = + IRQ_WORK_INIT_HARD(irq_work_wake); +#endif + +static int irq_workd_should_run(unsigned int cpu) +{ + return !llist_empty(this_cpu_ptr(&lazy_list)); +} /* * Claim the entry so that no one else will poke at it. @@ -52,15 +77,29 @@ void __weak arch_irq_work_raise(void) /* Enqueue on current CPU, work must already be claimed and preempt disabled */ static void __irq_work_queue_local(struct irq_work *work) { + struct llist_head *list; + bool rt_lazy_work = false; + bool lazy_work = false; + int work_flags; + + work_flags = atomic_read(&work->node.a_flags); + if (work_flags & IRQ_WORK_LAZY) + lazy_work = true; + else if (IS_ENABLED(CONFIG_PREEMPT_RT) && + !(work_flags & IRQ_WORK_HARD_IRQ)) + rt_lazy_work = true; + + if (lazy_work || rt_lazy_work) + list = this_cpu_ptr(&lazy_list); + else + list = this_cpu_ptr(&raised_list); + + if (!llist_add(&work->node.llist, list)) + return; + /* If the work is "lazy", handle it from next tick if any */ - if (atomic_read(&work->node.a_flags) & IRQ_WORK_LAZY) { - if (llist_add(&work->node.llist, this_cpu_ptr(&lazy_list)) && - tick_nohz_tick_stopped()) - arch_irq_work_raise(); - } else { - if (llist_add(&work->node.llist, this_cpu_ptr(&raised_list))) - arch_irq_work_raise(); - } + if (!lazy_work || tick_nohz_tick_stopped()) + arch_irq_work_raise(); } /* Enqueue the irq work @work on the current CPU */ @@ -104,17 +143,34 @@ bool irq_work_queue_on(struct irq_work *work, int cpu) if (cpu != smp_processor_id()) { /* Arch remote IPI send/receive backend aren't NMI safe */ WARN_ON_ONCE(in_nmi()); + + /* + * On PREEMPT_RT the items which are not marked as + * IRQ_WORK_HARD_IRQ are added to the lazy list and a HARD work + * item is used on the remote CPU to wake the thread. + */ + if (IS_ENABLED(CONFIG_PREEMPT_RT) && + !(atomic_read(&work->node.a_flags) & IRQ_WORK_HARD_IRQ)) { + + if (!llist_add(&work->node.llist, &per_cpu(lazy_list, cpu))) + goto out; + + work = &per_cpu(irq_work_wakeup, cpu); + if (!irq_work_claim(work)) + goto out; + } + __smp_call_single_queue(cpu, &work->node.llist); } else { __irq_work_queue_local(work); } +out: preempt_enable(); return true; #endif /* CONFIG_SMP */ } - bool irq_work_needs_cpu(void) { struct llist_head *raised, *lazy; @@ -170,7 +226,12 @@ static void irq_work_run_list(struct llist_head *list) struct irq_work *work, *tmp; struct llist_node *llnode; - BUG_ON(!irqs_disabled()); + /* + * On PREEMPT_RT IRQ-work which is not marked as HARD will be processed + * in a per-CPU thread in preemptible context. Only the items which are + * marked as IRQ_WORK_HARD_IRQ will be processed in hardirq context. + */ + BUG_ON(!irqs_disabled() && !IS_ENABLED(CONFIG_PREEMPT_RT)); if (llist_empty(list)) return; @@ -187,7 +248,10 @@ static void irq_work_run_list(struct llist_head *list) void irq_work_run(void) { irq_work_run_list(this_cpu_ptr(&raised_list)); - irq_work_run_list(this_cpu_ptr(&lazy_list)); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + irq_work_run_list(this_cpu_ptr(&lazy_list)); + else + wake_irq_workd(); } EXPORT_SYMBOL_GPL(irq_work_run); @@ -197,7 +261,11 @@ void irq_work_tick(void) if (!llist_empty(raised) && !arch_irq_work_has_interrupt()) irq_work_run_list(raised); - irq_work_run_list(this_cpu_ptr(&lazy_list)); + + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + irq_work_run_list(this_cpu_ptr(&lazy_list)); + else + wake_irq_workd(); } /* @@ -219,3 +287,29 @@ void irq_work_sync(struct irq_work *work) cpu_relax(); } EXPORT_SYMBOL_GPL(irq_work_sync); + +static void run_irq_workd(unsigned int cpu) +{ + irq_work_run_list(this_cpu_ptr(&lazy_list)); +} + +static void irq_workd_setup(unsigned int cpu) +{ + sched_set_fifo_low(current); +} + +static struct smp_hotplug_thread irqwork_threads = { + .store = &irq_workd, + .setup = irq_workd_setup, + .thread_should_run = irq_workd_should_run, + .thread_fn = run_irq_workd, + .thread_comm = "irq_work/%u", +}; + +static __init int irq_work_init_threads(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + BUG_ON(smpboot_register_percpu_thread(&irqwork_threads)); + return 0; +} +early_initcall(irq_work_init_threads); |