kernel/irq_work.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra
   4  *
   5  * Provides a framework for enqueueing and running callbacks from hardirq
   6  * context. The enqueueing is NMI-safe.
   7  */
   8
   9 #include <linux/bug.h>
  10 #include <linux/kernel.h>
  11 #include <linux/export.h>
  12 #include <linux/irq_work.h>
  13 #include <linux/percpu.h>
  14 #include <linux/hardirq.h>
  15 #include <linux/irqflags.h>
  16 #include <linux/sched.h>
  17 #include <linux/tick.h>
  18 #include <linux/cpu.h>
  19 #include <linux/notifier.h>
  20 #include <linux/smp.h>
  21 #include <asm/processor.h>
  22
  23
  24 static DEFINE_PER_CPU(struct llist_head, raised_list);
  25 static DEFINE_PER_CPU(struct llist_head, lazy_list);
  26
  27 /*
  28  * Claim the entry so that no one else will poke at it.
  29  */
  30 static bool irq_work_claim(struct irq_work *work)
  31 {
  32         int oflags;
  33
  34         oflags = atomic_fetch_or(IRQ_WORK_CLAIMED, &work->flags);
  35         /*
  36          * If the work is already pending, no need to raise the IPI.
  37          * The pairing atomic_fetch_andnot() in irq_work_run() makes sure
  38          * everything we did before is visible.
  39          */
  40         if (oflags & IRQ_WORK_PENDING)
  41                 return false;
  42         return true;
  43 }
  44
  45 void __weak arch_irq_work_raise(void)
  46 {
  47         /*
  48          * Lame architectures will get the timer tick callback
  49          */
  50 }
  51
  52 /* Enqueue on current CPU, work must already be claimed and preempt disabled */
  53 static void __irq_work_queue_local(struct irq_work *work)
  54 {
  55         /* If the work is "lazy", handle it from next tick if any */
  56         if (atomic_read(&work->flags) & IRQ_WORK_LAZY) {
  57                 if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
  58                     tick_nohz_tick_stopped())
  59                         arch_irq_work_raise();
  60         } else {
  61                 if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
  62                         arch_irq_work_raise();
  63         }
  64 }
  65
  66 /* Enqueue the irq work @work on the current CPU */
  67 bool irq_work_queue(struct irq_work *work)
  68 {
  69         /* Only queue if not already pending */
  70         if (!irq_work_claim(work))
  71                 return false;
  72
  73         /* Queue the entry and raise the IPI if needed. */
  74         preempt_disable();
  75         __irq_work_queue_local(work);
  76         preempt_enable();
  77
  78         return true;
  79 }
  80 EXPORT_SYMBOL_GPL(irq_work_queue);
  81
  82 /*
  83  * Enqueue the irq_work @work on @cpu unless it's already pending
  84  * somewhere.
  85  *
  86  * Can be re-enqueued while the callback is still in progress.
  87  */
  88 bool irq_work_queue_on(struct irq_work *work, int cpu)
  89 {
  90 #ifndef CONFIG_SMP
  91         return irq_work_queue(work);
  92
  93 #else /* CONFIG_SMP: */
  94         /* All work should have been flushed before going offline */
  95         WARN_ON_ONCE(cpu_is_offline(cpu));
  96
  97         /* Only queue if not already pending */
  98         if (!irq_work_claim(work))
  99                 return false;
 100
 101         preempt_disable();
 102         if (cpu != smp_processor_id()) {
 103                 /* Arch remote IPI send/receive backend aren't NMI safe */
 104                 WARN_ON_ONCE(in_nmi());
 105                 if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
 106                         arch_send_call_function_single_ipi(cpu);
 107         } else {
 108                 __irq_work_queue_local(work);
 109         }
 110         preempt_enable();
 111
 112         return true;
 113 #endif /* CONFIG_SMP */
 114 }
 115
 116
 117 bool irq_work_needs_cpu(void)
 118 {
 119         struct llist_head *raised, *lazy;
 120
 121         raised = this_cpu_ptr(&raised_list);
 122         lazy = this_cpu_ptr(&lazy_list);
 123
 124         if (llist_empty(raised) || arch_irq_work_has_interrupt())
 125                 if (llist_empty(lazy))
 126                         return false;
 127
 128         /* All work should have been flushed before going offline */
 129         WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
 130
 131         return true;
 132 }
 133
 134 static void irq_work_run_list(struct llist_head *list)
 135 {
 136         struct irq_work *work, *tmp;
 137         struct llist_node *llnode;
 138
 139         BUG_ON(!irqs_disabled());
 140
 141         if (llist_empty(list))
 142                 return;
 143
 144         llnode = llist_del_all(list);
 145         llist_for_each_entry_safe(work, tmp, llnode, llnode) {
 146                 int flags;
 147                 /*
 148                  * Clear the PENDING bit, after this point the @work
 149                  * can be re-used.
 150                  * Make it immediately visible so that other CPUs trying
 151                  * to claim that work don't rely on us to handle their data
 152                  * while we are in the middle of the func.
 153                  */
 154                 flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags);
 155
 156                 work->func(work);
 157                 /*
 158                  * Clear the BUSY bit and return to the free state if
 159                  * no-one else claimed it meanwhile.
 160                  */
 161                 flags &= ~IRQ_WORK_PENDING;
 162                 (void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
 163         }
 164 }
 165
 166 /*
 167  * hotplug calls this through:
 168  *  hotplug_cfd() -> flush_smp_call_function_queue()
 169  */
 170 void irq_work_run(void)
 171 {
 172         irq_work_run_list(this_cpu_ptr(&raised_list));
 173         irq_work_run_list(this_cpu_ptr(&lazy_list));
 174 }
 175 EXPORT_SYMBOL_GPL(irq_work_run);
 176
 177 void irq_work_tick(void)
 178 {
 179         struct llist_head *raised = this_cpu_ptr(&raised_list);
 180
 181         if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
 182                 irq_work_run_list(raised);
 183         irq_work_run_list(this_cpu_ptr(&lazy_list));
 184 }
 185
 186 /*
 187  * Synchronize against the irq_work @entry, ensures the entry is not
 188  * currently in use.
 189  */
 190 void irq_work_sync(struct irq_work *work)
 191 {
 192         lockdep_assert_irqs_enabled();
 193
 194         while (atomic_read(&work->flags) & IRQ_WORK_BUSY)
 195                 cpu_relax();
 196 }
 197 EXPORT_SYMBOL_GPL(irq_work_sync);