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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_FLAGS;
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#ifdef CONFIG_SMP
60/*
61 * Enqueue the irq_work @work on @cpu unless it's already pending
62 * somewhere.
63 *
64 * Can be re-enqueued while the callback is still in progress.
65 */
66bool irq_work_queue_on(struct irq_work *work, int cpu)
67{
68 /* All work should have been flushed before going offline */
69 WARN_ON_ONCE(cpu_is_offline(cpu));
70
71 /* Arch remote IPI send/receive backend aren't NMI safe */
72 WARN_ON_ONCE(in_nmi());
73
74 /* Only queue if not already pending */
75 if (!irq_work_claim(work))
76 return false;
77
78 if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
79 arch_send_call_function_single_ipi(cpu);
80
81 return true;
82}
83EXPORT_SYMBOL_GPL(irq_work_queue_on);
84#endif
85
86/* Enqueue the irq work @work on the current CPU */
87bool irq_work_queue(struct irq_work *work)
88{
89 /* Only queue if not already pending */
90 if (!irq_work_claim(work))
91 return false;
92
93 /* Queue the entry and raise the IPI if needed. */
94 preempt_disable();
95
96 /* If the work is "lazy", handle it from next tick if any */
97 if (work->flags & IRQ_WORK_LAZY) {
98 if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
99 tick_nohz_tick_stopped())
100 arch_irq_work_raise();
101 } else {
102 if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
103 arch_irq_work_raise();
104 }
105
106 preempt_enable();
107
108 return true;
109}
110EXPORT_SYMBOL_GPL(irq_work_queue);
111
112bool irq_work_needs_cpu(void)
113{
114 struct llist_head *raised, *lazy;
115
116 raised = this_cpu_ptr(&raised_list);
117 lazy = this_cpu_ptr(&lazy_list);
118
119 if (llist_empty(raised) || arch_irq_work_has_interrupt())
120 if (llist_empty(lazy))
121 return false;
122
123 /* All work should have been flushed before going offline */
124 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
125
126 return true;
127}
128
129static void irq_work_run_list(struct llist_head *list)
130{
131 unsigned long flags;
132 struct irq_work *work;
133 struct llist_node *llnode;
134
135 BUG_ON(!irqs_disabled());
136
137 if (llist_empty(list))
138 return;
139
140 llnode = llist_del_all(list);
141 while (llnode != NULL) {
142 work = llist_entry(llnode, struct irq_work, llnode);
143
144 llnode = llist_next(llnode);
145
146 /*
147 * Clear the PENDING bit, after this point the @work
148 * can be re-used.
149 * Make it immediately visible so that other CPUs trying
150 * to claim that work don't rely on us to handle their data
151 * while we are in the middle of the func.
152 */
153 flags = work->flags & ~IRQ_WORK_PENDING;
154 xchg(&work->flags, 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 (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
162 }
163}
164
165/*
166 * hotplug calls this through:
167 * hotplug_cfd() -> flush_smp_call_function_queue()
168 */
169void irq_work_run(void)
170{
171 irq_work_run_list(this_cpu_ptr(&raised_list));
172 irq_work_run_list(this_cpu_ptr(&lazy_list));
173}
174EXPORT_SYMBOL_GPL(irq_work_run);
175
176void irq_work_tick(void)
177{
178 struct llist_head *raised = this_cpu_ptr(&raised_list);
179
180 if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
181 irq_work_run_list(raised);
182 irq_work_run_list(this_cpu_ptr(&lazy_list));
183}
184
185/*
186 * Synchronize against the irq_work @entry, ensures the entry is not
187 * currently in use.
188 */
189void irq_work_sync(struct irq_work *work)
190{
191 WARN_ON_ONCE(irqs_disabled());
192
193 while (work->flags & IRQ_WORK_BUSY)
194 cpu_relax();
195}
196EXPORT_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);