Loading...
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);
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 <linux/smpboot.h>
22#include <asm/processor.h>
23#include <linux/kasan.h>
24
25static DEFINE_PER_CPU(struct llist_head, raised_list);
26static DEFINE_PER_CPU(struct llist_head, lazy_list);
27static DEFINE_PER_CPU(struct task_struct *, irq_workd);
28
29static void wake_irq_workd(void)
30{
31 struct task_struct *tsk = __this_cpu_read(irq_workd);
32
33 if (!llist_empty(this_cpu_ptr(&lazy_list)) && tsk)
34 wake_up_process(tsk);
35}
36
37#ifdef CONFIG_SMP
38static void irq_work_wake(struct irq_work *entry)
39{
40 wake_irq_workd();
41}
42
43static DEFINE_PER_CPU(struct irq_work, irq_work_wakeup) =
44 IRQ_WORK_INIT_HARD(irq_work_wake);
45#endif
46
47static int irq_workd_should_run(unsigned int cpu)
48{
49 return !llist_empty(this_cpu_ptr(&lazy_list));
50}
51
52/*
53 * Claim the entry so that no one else will poke at it.
54 */
55static bool irq_work_claim(struct irq_work *work)
56{
57 int oflags;
58
59 oflags = atomic_fetch_or(IRQ_WORK_CLAIMED | CSD_TYPE_IRQ_WORK, &work->node.a_flags);
60 /*
61 * If the work is already pending, no need to raise the IPI.
62 * The pairing smp_mb() in irq_work_single() makes sure
63 * everything we did before is visible.
64 */
65 if (oflags & IRQ_WORK_PENDING)
66 return false;
67 return true;
68}
69
70void __weak arch_irq_work_raise(void)
71{
72 /*
73 * Lame architectures will get the timer tick callback
74 */
75}
76
77/* Enqueue on current CPU, work must already be claimed and preempt disabled */
78static void __irq_work_queue_local(struct irq_work *work)
79{
80 struct llist_head *list;
81 bool rt_lazy_work = false;
82 bool lazy_work = false;
83 int work_flags;
84
85 work_flags = atomic_read(&work->node.a_flags);
86 if (work_flags & IRQ_WORK_LAZY)
87 lazy_work = true;
88 else if (IS_ENABLED(CONFIG_PREEMPT_RT) &&
89 !(work_flags & IRQ_WORK_HARD_IRQ))
90 rt_lazy_work = true;
91
92 if (lazy_work || rt_lazy_work)
93 list = this_cpu_ptr(&lazy_list);
94 else
95 list = this_cpu_ptr(&raised_list);
96
97 if (!llist_add(&work->node.llist, list))
98 return;
99
100 /* If the work is "lazy", handle it from next tick if any */
101 if (!lazy_work || tick_nohz_tick_stopped())
102 arch_irq_work_raise();
103}
104
105/* Enqueue the irq work @work on the current CPU */
106bool irq_work_queue(struct irq_work *work)
107{
108 /* Only queue if not already pending */
109 if (!irq_work_claim(work))
110 return false;
111
112 /* Queue the entry and raise the IPI if needed. */
113 preempt_disable();
114 __irq_work_queue_local(work);
115 preempt_enable();
116
117 return true;
118}
119EXPORT_SYMBOL_GPL(irq_work_queue);
120
121/*
122 * Enqueue the irq_work @work on @cpu unless it's already pending
123 * somewhere.
124 *
125 * Can be re-enqueued while the callback is still in progress.
126 */
127bool irq_work_queue_on(struct irq_work *work, int cpu)
128{
129#ifndef CONFIG_SMP
130 return irq_work_queue(work);
131
132#else /* CONFIG_SMP: */
133 /* All work should have been flushed before going offline */
134 WARN_ON_ONCE(cpu_is_offline(cpu));
135
136 /* Only queue if not already pending */
137 if (!irq_work_claim(work))
138 return false;
139
140 kasan_record_aux_stack_noalloc(work);
141
142 preempt_disable();
143 if (cpu != smp_processor_id()) {
144 /* Arch remote IPI send/receive backend aren't NMI safe */
145 WARN_ON_ONCE(in_nmi());
146
147 /*
148 * On PREEMPT_RT the items which are not marked as
149 * IRQ_WORK_HARD_IRQ are added to the lazy list and a HARD work
150 * item is used on the remote CPU to wake the thread.
151 */
152 if (IS_ENABLED(CONFIG_PREEMPT_RT) &&
153 !(atomic_read(&work->node.a_flags) & IRQ_WORK_HARD_IRQ)) {
154
155 if (!llist_add(&work->node.llist, &per_cpu(lazy_list, cpu)))
156 goto out;
157
158 work = &per_cpu(irq_work_wakeup, cpu);
159 if (!irq_work_claim(work))
160 goto out;
161 }
162
163 __smp_call_single_queue(cpu, &work->node.llist);
164 } else {
165 __irq_work_queue_local(work);
166 }
167out:
168 preempt_enable();
169
170 return true;
171#endif /* CONFIG_SMP */
172}
173
174bool irq_work_needs_cpu(void)
175{
176 struct llist_head *raised, *lazy;
177
178 raised = this_cpu_ptr(&raised_list);
179 lazy = this_cpu_ptr(&lazy_list);
180
181 if (llist_empty(raised) || arch_irq_work_has_interrupt())
182 if (llist_empty(lazy))
183 return false;
184
185 /* All work should have been flushed before going offline */
186 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
187
188 return true;
189}
190
191void irq_work_single(void *arg)
192{
193 struct irq_work *work = arg;
194 int flags;
195
196 /*
197 * Clear the PENDING bit, after this point the @work can be re-used.
198 * The PENDING bit acts as a lock, and we own it, so we can clear it
199 * without atomic ops.
200 */
201 flags = atomic_read(&work->node.a_flags);
202 flags &= ~IRQ_WORK_PENDING;
203 atomic_set(&work->node.a_flags, flags);
204
205 /*
206 * See irq_work_claim().
207 */
208 smp_mb();
209
210 lockdep_irq_work_enter(flags);
211 work->func(work);
212 lockdep_irq_work_exit(flags);
213
214 /*
215 * Clear the BUSY bit, if set, and return to the free state if no-one
216 * else claimed it meanwhile.
217 */
218 (void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY);
219
220 if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
221 !arch_irq_work_has_interrupt())
222 rcuwait_wake_up(&work->irqwait);
223}
224
225static void irq_work_run_list(struct llist_head *list)
226{
227 struct irq_work *work, *tmp;
228 struct llist_node *llnode;
229
230 /*
231 * On PREEMPT_RT IRQ-work which is not marked as HARD will be processed
232 * in a per-CPU thread in preemptible context. Only the items which are
233 * marked as IRQ_WORK_HARD_IRQ will be processed in hardirq context.
234 */
235 BUG_ON(!irqs_disabled() && !IS_ENABLED(CONFIG_PREEMPT_RT));
236
237 if (llist_empty(list))
238 return;
239
240 llnode = llist_del_all(list);
241 llist_for_each_entry_safe(work, tmp, llnode, node.llist)
242 irq_work_single(work);
243}
244
245/*
246 * hotplug calls this through:
247 * hotplug_cfd() -> flush_smp_call_function_queue()
248 */
249void irq_work_run(void)
250{
251 irq_work_run_list(this_cpu_ptr(&raised_list));
252 if (!IS_ENABLED(CONFIG_PREEMPT_RT))
253 irq_work_run_list(this_cpu_ptr(&lazy_list));
254 else
255 wake_irq_workd();
256}
257EXPORT_SYMBOL_GPL(irq_work_run);
258
259void irq_work_tick(void)
260{
261 struct llist_head *raised = this_cpu_ptr(&raised_list);
262
263 if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
264 irq_work_run_list(raised);
265
266 if (!IS_ENABLED(CONFIG_PREEMPT_RT))
267 irq_work_run_list(this_cpu_ptr(&lazy_list));
268 else
269 wake_irq_workd();
270}
271
272/*
273 * Synchronize against the irq_work @entry, ensures the entry is not
274 * currently in use.
275 */
276void irq_work_sync(struct irq_work *work)
277{
278 lockdep_assert_irqs_enabled();
279 might_sleep();
280
281 if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
282 !arch_irq_work_has_interrupt()) {
283 rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work),
284 TASK_UNINTERRUPTIBLE);
285 return;
286 }
287
288 while (irq_work_is_busy(work))
289 cpu_relax();
290}
291EXPORT_SYMBOL_GPL(irq_work_sync);
292
293static void run_irq_workd(unsigned int cpu)
294{
295 irq_work_run_list(this_cpu_ptr(&lazy_list));
296}
297
298static void irq_workd_setup(unsigned int cpu)
299{
300 sched_set_fifo_low(current);
301}
302
303static struct smp_hotplug_thread irqwork_threads = {
304 .store = &irq_workd,
305 .setup = irq_workd_setup,
306 .thread_should_run = irq_workd_should_run,
307 .thread_fn = run_irq_workd,
308 .thread_comm = "irq_work/%u",
309};
310
311static __init int irq_work_init_threads(void)
312{
313 if (IS_ENABLED(CONFIG_PREEMPT_RT))
314 BUG_ON(smpboot_register_percpu_thread(&irqwork_threads));
315 return 0;
316}
317early_initcall(irq_work_init_threads);