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 #include <linux/kasan.h>
  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 | CSD_TYPE_IRQ_WORK, &work->node.a_flags);
  35         /*
  36          * If the work is already pending, no need to raise the IPI.
  37          * The pairing smp_mb() in irq_work_single() 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->node.a_flags) & IRQ_WORK_LAZY) {
  57                 if (llist_add(&work->node.llist, this_cpu_ptr(&lazy_list)) &&
  58                     tick_nohz_tick_stopped())
  59                         arch_irq_work_raise();
  60         } else {
  61                 if (llist_add(&work->node.llist, 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         /*record irq_work call stack in order to print it in KASAN reports*/
  74         kasan_record_aux_stack(work);
  75
  76         /* Queue the entry and raise the IPI if needed. */
  77         preempt_disable();
  78         __irq_work_queue_local(work);
  79         preempt_enable();
  80
  81         return true;
  82 }
  83 EXPORT_SYMBOL_GPL(irq_work_queue);
  84
  85 /*
  86  * Enqueue the irq_work @work on @cpu unless it's already pending
  87  * somewhere.
  88  *
  89  * Can be re-enqueued while the callback is still in progress.
  90  */
  91 bool irq_work_queue_on(struct irq_work *work, int cpu)
  92 {
  93 #ifndef CONFIG_SMP
  94         return irq_work_queue(work);
  95
  96 #else /* CONFIG_SMP: */
  97         /* All work should have been flushed before going offline */
  98         WARN_ON_ONCE(cpu_is_offline(cpu));
  99
 100         /* Only queue if not already pending */
 101         if (!irq_work_claim(work))
 102                 return false;
 103
 104         kasan_record_aux_stack(work);
 105
 106         preempt_disable();
 107         if (cpu != smp_processor_id()) {
 108                 /* Arch remote IPI send/receive backend aren't NMI safe */
 109                 WARN_ON_ONCE(in_nmi());
 110                 __smp_call_single_queue(cpu, &work->node.llist);
 111         } else {
 112                 __irq_work_queue_local(work);
 113         }
 114         preempt_enable();
 115
 116         return true;
 117 #endif /* CONFIG_SMP */
 118 }
 119
 120
 121 bool irq_work_needs_cpu(void)
 122 {
 123         struct llist_head *raised, *lazy;
 124
 125         raised = this_cpu_ptr(&raised_list);
 126         lazy = this_cpu_ptr(&lazy_list);
 127
 128         if (llist_empty(raised) || arch_irq_work_has_interrupt())
 129                 if (llist_empty(lazy))
 130                         return false;
 131
 132         /* All work should have been flushed before going offline */
 133         WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
 134
 135         return true;
 136 }
 137
 138 void irq_work_single(void *arg)
 139 {
 140         struct irq_work *work = arg;
 141         int flags;
 142
 143         /*
 144          * Clear the PENDING bit, after this point the @work can be re-used.
 145          * The PENDING bit acts as a lock, and we own it, so we can clear it
 146          * without atomic ops.
 147          */
 148         flags = atomic_read(&work->node.a_flags);
 149         flags &= ~IRQ_WORK_PENDING;
 150         atomic_set(&work->node.a_flags, flags);
 151
 152         /*
 153          * See irq_work_claim().
 154          */
 155         smp_mb();
 156
 157         lockdep_irq_work_enter(flags);
 158         work->func(work);
 159         lockdep_irq_work_exit(flags);
 160
 161         /*
 162          * Clear the BUSY bit, if set, and return to the free state if no-one
 163          * else claimed it meanwhile.
 164          */
 165         (void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY);
 166 }
 167
 168 static void irq_work_run_list(struct llist_head *list)
 169 {
 170         struct irq_work *work, *tmp;
 171         struct llist_node *llnode;
 172
 173         BUG_ON(!irqs_disabled());
 174
 175         if (llist_empty(list))
 176                 return;
 177
 178         llnode = llist_del_all(list);
 179         llist_for_each_entry_safe(work, tmp, llnode, node.llist)
 180                 irq_work_single(work);
 181 }
 182
 183 /*
 184  * hotplug calls this through:
 185  *  hotplug_cfd() -> flush_smp_call_function_queue()
 186  */
 187 void irq_work_run(void)
 188 {
 189         irq_work_run_list(this_cpu_ptr(&raised_list));
 190         irq_work_run_list(this_cpu_ptr(&lazy_list));
 191 }
 192 EXPORT_SYMBOL_GPL(irq_work_run);
 193
 194 void irq_work_tick(void)
 195 {
 196         struct llist_head *raised = this_cpu_ptr(&raised_list);
 197
 198         if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
 199                 irq_work_run_list(raised);
 200         irq_work_run_list(this_cpu_ptr(&lazy_list));
 201 }
 202
 203 /*
 204  * Synchronize against the irq_work @entry, ensures the entry is not
 205  * currently in use.
 206  */
 207 void irq_work_sync(struct irq_work *work)
 208 {
 209         lockdep_assert_irqs_enabled();
 210
 211         while (irq_work_is_busy(work))
 212                 cpu_relax();
 213 }
 214 EXPORT_SYMBOL_GPL(irq_work_sync);