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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/*
2 * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra
3 *
4 * Provides a framework for enqueueing and running callbacks from hardirq
5 * context. The enqueueing is NMI-safe.
6 */
7
8#include <linux/bug.h>
9#include <linux/kernel.h>
10#include <linux/export.h>
11#include <linux/irq_work.h>
12#include <linux/percpu.h>
13#include <linux/hardirq.h>
14#include <linux/irqflags.h>
15#include <linux/sched.h>
16#include <linux/tick.h>
17#include <linux/cpu.h>
18#include <linux/notifier.h>
19#include <linux/smp.h>
20#include <asm/processor.h>
21
22
23static DEFINE_PER_CPU(struct llist_head, raised_list);
24static DEFINE_PER_CPU(struct llist_head, lazy_list);
25
26/*
27 * Claim the entry so that no one else will poke at it.
28 */
29static bool irq_work_claim(struct irq_work *work)
30{
31 unsigned long flags, oflags, nflags;
32
33 /*
34 * Start with our best wish as a premise but only trust any
35 * flag value after cmpxchg() result.
36 */
37 flags = work->flags & ~IRQ_WORK_PENDING;
38 for (;;) {
39 nflags = flags | IRQ_WORK_CLAIMED;
40 oflags = cmpxchg(&work->flags, flags, nflags);
41 if (oflags == flags)
42 break;
43 if (oflags & IRQ_WORK_PENDING)
44 return false;
45 flags = oflags;
46 cpu_relax();
47 }
48
49 return true;
50}
51
52void __weak arch_irq_work_raise(void)
53{
54 /*
55 * Lame architectures will get the timer tick callback
56 */
57}
58
59/*
60 * Enqueue the irq_work @work on @cpu unless it's already pending
61 * somewhere.
62 *
63 * Can be re-enqueued while the callback is still in progress.
64 */
65bool irq_work_queue_on(struct irq_work *work, int cpu)
66{
67 /* All work should have been flushed before going offline */
68 WARN_ON_ONCE(cpu_is_offline(cpu));
69
70#ifdef CONFIG_SMP
71
72 /* Arch remote IPI send/receive backend aren't NMI safe */
73 WARN_ON_ONCE(in_nmi());
74
75 /* Only queue if not already pending */
76 if (!irq_work_claim(work))
77 return false;
78
79 if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
80 arch_send_call_function_single_ipi(cpu);
81
82#else /* #ifdef CONFIG_SMP */
83 irq_work_queue(work);
84#endif /* #else #ifdef CONFIG_SMP */
85
86 return true;
87}
88
89/* Enqueue the irq work @work on the current CPU */
90bool irq_work_queue(struct irq_work *work)
91{
92 /* Only queue if not already pending */
93 if (!irq_work_claim(work))
94 return false;
95
96 /* Queue the entry and raise the IPI if needed. */
97 preempt_disable();
98
99 /* If the work is "lazy", handle it from next tick if any */
100 if (work->flags & IRQ_WORK_LAZY) {
101 if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
102 tick_nohz_tick_stopped())
103 arch_irq_work_raise();
104 } else {
105 if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
106 arch_irq_work_raise();
107 }
108
109 preempt_enable();
110
111 return true;
112}
113EXPORT_SYMBOL_GPL(irq_work_queue);
114
115bool irq_work_needs_cpu(void)
116{
117 struct llist_head *raised, *lazy;
118
119 raised = this_cpu_ptr(&raised_list);
120 lazy = this_cpu_ptr(&lazy_list);
121
122 if (llist_empty(raised) || arch_irq_work_has_interrupt())
123 if (llist_empty(lazy))
124 return false;
125
126 /* All work should have been flushed before going offline */
127 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
128
129 return true;
130}
131
132static void irq_work_run_list(struct llist_head *list)
133{
134 struct irq_work *work, *tmp;
135 struct llist_node *llnode;
136 unsigned long flags;
137
138 BUG_ON(!irqs_disabled());
139
140 if (llist_empty(list))
141 return;
142
143 llnode = llist_del_all(list);
144 llist_for_each_entry_safe(work, tmp, llnode, llnode) {
145 /*
146 * Clear the PENDING bit, after this point the @work
147 * can be re-used.
148 * Make it immediately visible so that other CPUs trying
149 * to claim that work don't rely on us to handle their data
150 * while we are in the middle of the func.
151 */
152 flags = work->flags & ~IRQ_WORK_PENDING;
153 xchg(&work->flags, flags);
154
155 work->func(work);
156 /*
157 * Clear the BUSY bit and return to the free state if
158 * no-one else claimed it meanwhile.
159 */
160 (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
161 }
162}
163
164/*
165 * hotplug calls this through:
166 * hotplug_cfd() -> flush_smp_call_function_queue()
167 */
168void irq_work_run(void)
169{
170 irq_work_run_list(this_cpu_ptr(&raised_list));
171 irq_work_run_list(this_cpu_ptr(&lazy_list));
172}
173EXPORT_SYMBOL_GPL(irq_work_run);
174
175void irq_work_tick(void)
176{
177 struct llist_head *raised = this_cpu_ptr(&raised_list);
178
179 if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
180 irq_work_run_list(raised);
181 irq_work_run_list(this_cpu_ptr(&lazy_list));
182}
183
184/*
185 * Synchronize against the irq_work @entry, ensures the entry is not
186 * currently in use.
187 */
188void irq_work_sync(struct irq_work *work)
189{
190 lockdep_assert_irqs_enabled();
191
192 while (work->flags & IRQ_WORK_BUSY)
193 cpu_relax();
194}
195EXPORT_SYMBOL_GPL(irq_work_sync);