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 unsigned long flags, oflags, nflags; 33 34 /* 35 * Start with our best wish as a premise but only trust any 36 * flag value after cmpxchg() result. 37 */ 38 flags = work->flags & ~IRQ_WORK_PENDING; 39 for (;;) { 40 nflags = flags | IRQ_WORK_CLAIMED; 41 oflags = cmpxchg(&work->flags, flags, nflags); 42 if (oflags == flags) 43 break; 44 if (oflags & IRQ_WORK_PENDING) 45 return false; 46 flags = oflags; 47 cpu_relax(); 48 } 49 50 return true; 51 } 52 53 void __weak arch_irq_work_raise(void) 54 { 55 /* 56 * Lame architectures will get the timer tick callback 57 */ 58 } 59 60 /* Enqueue on current CPU, work must already be claimed and preempt disabled */ 61 static void __irq_work_queue_local(struct irq_work *work) 62 { 63 /* If the work is "lazy", handle it from next tick if any */ 64 if (work->flags & IRQ_WORK_LAZY) { 65 if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) && 66 tick_nohz_tick_stopped()) 67 arch_irq_work_raise(); 68 } else { 69 if (llist_add(&work->llnode, this_cpu_ptr(&raised_list))) 70 arch_irq_work_raise(); 71 } 72 } 73 74 /* Enqueue the irq work @work on the current CPU */ 75 bool irq_work_queue(struct irq_work *work) 76 { 77 /* Only queue if not already pending */ 78 if (!irq_work_claim(work)) 79 return false; 80 81 /* Queue the entry and raise the IPI if needed. */ 82 preempt_disable(); 83 __irq_work_queue_local(work); 84 preempt_enable(); 85 86 return true; 87 } 88 EXPORT_SYMBOL_GPL(irq_work_queue); 89 90 /* 91 * Enqueue the irq_work @work on @cpu unless it's already pending 92 * somewhere. 93 * 94 * Can be re-enqueued while the callback is still in progress. 95 */ 96 bool irq_work_queue_on(struct irq_work *work, int cpu) 97 { 98 #ifndef CONFIG_SMP 99 return irq_work_queue(work); 100 101 #else /* CONFIG_SMP: */ 102 /* All work should have been flushed before going offline */ 103 WARN_ON_ONCE(cpu_is_offline(cpu)); 104 105 /* Only queue if not already pending */ 106 if (!irq_work_claim(work)) 107 return false; 108 109 preempt_disable(); 110 if (cpu != smp_processor_id()) { 111 /* Arch remote IPI send/receive backend aren't NMI safe */ 112 WARN_ON_ONCE(in_nmi()); 113 if (llist_add(&work->llnode, &per_cpu(raised_list, cpu))) 114 arch_send_call_function_single_ipi(cpu); 115 } else { 116 __irq_work_queue_local(work); 117 } 118 preempt_enable(); 119 120 return true; 121 #endif /* CONFIG_SMP */ 122 } 123 124 125 bool irq_work_needs_cpu(void) 126 { 127 struct llist_head *raised, *lazy; 128 129 raised = this_cpu_ptr(&raised_list); 130 lazy = this_cpu_ptr(&lazy_list); 131 132 if (llist_empty(raised) || arch_irq_work_has_interrupt()) 133 if (llist_empty(lazy)) 134 return false; 135 136 /* All work should have been flushed before going offline */ 137 WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); 138 139 return true; 140 } 141 142 static void irq_work_run_list(struct llist_head *list) 143 { 144 struct irq_work *work, *tmp; 145 struct llist_node *llnode; 146 unsigned long flags; 147 148 BUG_ON(!irqs_disabled()); 149 150 if (llist_empty(list)) 151 return; 152 153 llnode = llist_del_all(list); 154 llist_for_each_entry_safe(work, tmp, llnode, llnode) { 155 /* 156 * Clear the PENDING bit, after this point the @work 157 * can be re-used. 158 * Make it immediately visible so that other CPUs trying 159 * to claim that work don't rely on us to handle their data 160 * while we are in the middle of the func. 161 */ 162 flags = work->flags & ~IRQ_WORK_PENDING; 163 xchg(&work->flags, flags); 164 165 work->func(work); 166 /* 167 * Clear the BUSY bit and return to the free state if 168 * no-one else claimed it meanwhile. 169 */ 170 (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY); 171 } 172 } 173 174 /* 175 * hotplug calls this through: 176 * hotplug_cfd() -> flush_smp_call_function_queue() 177 */ 178 void irq_work_run(void) 179 { 180 irq_work_run_list(this_cpu_ptr(&raised_list)); 181 irq_work_run_list(this_cpu_ptr(&lazy_list)); 182 } 183 EXPORT_SYMBOL_GPL(irq_work_run); 184 185 void irq_work_tick(void) 186 { 187 struct llist_head *raised = this_cpu_ptr(&raised_list); 188 189 if (!llist_empty(raised) && !arch_irq_work_has_interrupt()) 190 irq_work_run_list(raised); 191 irq_work_run_list(this_cpu_ptr(&lazy_list)); 192 } 193 194 /* 195 * Synchronize against the irq_work @entry, ensures the entry is not 196 * currently in use. 197 */ 198 void irq_work_sync(struct irq_work *work) 199 { 200 lockdep_assert_irqs_enabled(); 201 202 while (work->flags & IRQ_WORK_BUSY) 203 cpu_relax(); 204 } 205 EXPORT_SYMBOL_GPL(irq_work_sync); 206