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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
24static DEFINE_PER_CPU(struct llist_head, raised_list);
25static DEFINE_PER_CPU(struct llist_head, lazy_list);
26
27/*
28 * Claim the entry so that no one else will poke at it.
29 */
30static 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
53void __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 */
61static 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 */
75bool 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}
88EXPORT_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 */
96bool 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
125bool 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
142static 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 */
178void 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}
183EXPORT_SYMBOL_GPL(irq_work_run);
184
185void 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 */
198void 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}
205EXPORT_SYMBOL_GPL(irq_work_sync);
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
24static DEFINE_PER_CPU(struct llist_head, raised_list);
25static DEFINE_PER_CPU(struct llist_head, lazy_list);
26
27/*
28 * Claim the entry so that no one else will poke at it.
29 */
30static 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
45void __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 */
53static 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 */
67bool 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}
80EXPORT_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 */
88bool 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 kasan_record_aux_stack(work);
102
103 preempt_disable();
104 if (cpu != smp_processor_id()) {
105 /* Arch remote IPI send/receive backend aren't NMI safe */
106 WARN_ON_ONCE(in_nmi());
107 __smp_call_single_queue(cpu, &work->node.llist);
108 } else {
109 __irq_work_queue_local(work);
110 }
111 preempt_enable();
112
113 return true;
114#endif /* CONFIG_SMP */
115}
116
117
118bool irq_work_needs_cpu(void)
119{
120 struct llist_head *raised, *lazy;
121
122 raised = this_cpu_ptr(&raised_list);
123 lazy = this_cpu_ptr(&lazy_list);
124
125 if (llist_empty(raised) || arch_irq_work_has_interrupt())
126 if (llist_empty(lazy))
127 return false;
128
129 /* All work should have been flushed before going offline */
130 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
131
132 return true;
133}
134
135void irq_work_single(void *arg)
136{
137 struct irq_work *work = arg;
138 int flags;
139
140 /*
141 * Clear the PENDING bit, after this point the @work can be re-used.
142 * The PENDING bit acts as a lock, and we own it, so we can clear it
143 * without atomic ops.
144 */
145 flags = atomic_read(&work->node.a_flags);
146 flags &= ~IRQ_WORK_PENDING;
147 atomic_set(&work->node.a_flags, flags);
148
149 /*
150 * See irq_work_claim().
151 */
152 smp_mb();
153
154 lockdep_irq_work_enter(flags);
155 work->func(work);
156 lockdep_irq_work_exit(flags);
157
158 /*
159 * Clear the BUSY bit, if set, and return to the free state if no-one
160 * else claimed it meanwhile.
161 */
162 (void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY);
163}
164
165static void irq_work_run_list(struct llist_head *list)
166{
167 struct irq_work *work, *tmp;
168 struct llist_node *llnode;
169
170 BUG_ON(!irqs_disabled());
171
172 if (llist_empty(list))
173 return;
174
175 llnode = llist_del_all(list);
176 llist_for_each_entry_safe(work, tmp, llnode, node.llist)
177 irq_work_single(work);
178}
179
180/*
181 * hotplug calls this through:
182 * hotplug_cfd() -> flush_smp_call_function_queue()
183 */
184void irq_work_run(void)
185{
186 irq_work_run_list(this_cpu_ptr(&raised_list));
187 irq_work_run_list(this_cpu_ptr(&lazy_list));
188}
189EXPORT_SYMBOL_GPL(irq_work_run);
190
191void irq_work_tick(void)
192{
193 struct llist_head *raised = this_cpu_ptr(&raised_list);
194
195 if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
196 irq_work_run_list(raised);
197 irq_work_run_list(this_cpu_ptr(&lazy_list));
198}
199
200/*
201 * Synchronize against the irq_work @entry, ensures the entry is not
202 * currently in use.
203 */
204void irq_work_sync(struct irq_work *work)
205{
206 lockdep_assert_irqs_enabled();
207
208 while (irq_work_is_busy(work))
209 cpu_relax();
210}
211EXPORT_SYMBOL_GPL(irq_work_sync);