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); 215