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); 198