Loading...
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 <linux/smpboot.h>
22#include <asm/processor.h>
23#include <linux/kasan.h>
24
25#include <trace/events/ipi.h>
26
27static DEFINE_PER_CPU(struct llist_head, raised_list);
28static DEFINE_PER_CPU(struct llist_head, lazy_list);
29static DEFINE_PER_CPU(struct task_struct *, irq_workd);
30
31static void wake_irq_workd(void)
32{
33 struct task_struct *tsk = __this_cpu_read(irq_workd);
34
35 if (!llist_empty(this_cpu_ptr(&lazy_list)) && tsk)
36 wake_up_process(tsk);
37}
38
39#ifdef CONFIG_SMP
40static void irq_work_wake(struct irq_work *entry)
41{
42 wake_irq_workd();
43}
44
45static DEFINE_PER_CPU(struct irq_work, irq_work_wakeup) =
46 IRQ_WORK_INIT_HARD(irq_work_wake);
47#endif
48
49static int irq_workd_should_run(unsigned int cpu)
50{
51 return !llist_empty(this_cpu_ptr(&lazy_list));
52}
53
54/*
55 * Claim the entry so that no one else will poke at it.
56 */
57static bool irq_work_claim(struct irq_work *work)
58{
59 int oflags;
60
61 oflags = atomic_fetch_or(IRQ_WORK_CLAIMED | CSD_TYPE_IRQ_WORK, &work->node.a_flags);
62 /*
63 * If the work is already pending, no need to raise the IPI.
64 * The pairing smp_mb() in irq_work_single() makes sure
65 * everything we did before is visible.
66 */
67 if (oflags & IRQ_WORK_PENDING)
68 return false;
69 return true;
70}
71
72void __weak arch_irq_work_raise(void)
73{
74 /*
75 * Lame architectures will get the timer tick callback
76 */
77}
78
79static __always_inline void irq_work_raise(struct irq_work *work)
80{
81 if (trace_ipi_send_cpu_enabled() && arch_irq_work_has_interrupt())
82 trace_ipi_send_cpu(smp_processor_id(), _RET_IP_, work->func);
83
84 arch_irq_work_raise();
85}
86
87/* Enqueue on current CPU, work must already be claimed and preempt disabled */
88static void __irq_work_queue_local(struct irq_work *work)
89{
90 struct llist_head *list;
91 bool rt_lazy_work = false;
92 bool lazy_work = false;
93 int work_flags;
94
95 work_flags = atomic_read(&work->node.a_flags);
96 if (work_flags & IRQ_WORK_LAZY)
97 lazy_work = true;
98 else if (IS_ENABLED(CONFIG_PREEMPT_RT) &&
99 !(work_flags & IRQ_WORK_HARD_IRQ))
100 rt_lazy_work = true;
101
102 if (lazy_work || rt_lazy_work)
103 list = this_cpu_ptr(&lazy_list);
104 else
105 list = this_cpu_ptr(&raised_list);
106
107 if (!llist_add(&work->node.llist, list))
108 return;
109
110 /* If the work is "lazy", handle it from next tick if any */
111 if (!lazy_work || tick_nohz_tick_stopped())
112 irq_work_raise(work);
113}
114
115/* Enqueue the irq work @work on the current CPU */
116bool irq_work_queue(struct irq_work *work)
117{
118 /* Only queue if not already pending */
119 if (!irq_work_claim(work))
120 return false;
121
122 /* Queue the entry and raise the IPI if needed. */
123 preempt_disable();
124 __irq_work_queue_local(work);
125 preempt_enable();
126
127 return true;
128}
129EXPORT_SYMBOL_GPL(irq_work_queue);
130
131/*
132 * Enqueue the irq_work @work on @cpu unless it's already pending
133 * somewhere.
134 *
135 * Can be re-enqueued while the callback is still in progress.
136 */
137bool irq_work_queue_on(struct irq_work *work, int cpu)
138{
139#ifndef CONFIG_SMP
140 return irq_work_queue(work);
141
142#else /* CONFIG_SMP: */
143 /* All work should have been flushed before going offline */
144 WARN_ON_ONCE(cpu_is_offline(cpu));
145
146 /* Only queue if not already pending */
147 if (!irq_work_claim(work))
148 return false;
149
150 kasan_record_aux_stack_noalloc(work);
151
152 preempt_disable();
153 if (cpu != smp_processor_id()) {
154 /* Arch remote IPI send/receive backend aren't NMI safe */
155 WARN_ON_ONCE(in_nmi());
156
157 /*
158 * On PREEMPT_RT the items which are not marked as
159 * IRQ_WORK_HARD_IRQ are added to the lazy list and a HARD work
160 * item is used on the remote CPU to wake the thread.
161 */
162 if (IS_ENABLED(CONFIG_PREEMPT_RT) &&
163 !(atomic_read(&work->node.a_flags) & IRQ_WORK_HARD_IRQ)) {
164
165 if (!llist_add(&work->node.llist, &per_cpu(lazy_list, cpu)))
166 goto out;
167
168 work = &per_cpu(irq_work_wakeup, cpu);
169 if (!irq_work_claim(work))
170 goto out;
171 }
172
173 __smp_call_single_queue(cpu, &work->node.llist);
174 } else {
175 __irq_work_queue_local(work);
176 }
177out:
178 preempt_enable();
179
180 return true;
181#endif /* CONFIG_SMP */
182}
183
184bool irq_work_needs_cpu(void)
185{
186 struct llist_head *raised, *lazy;
187
188 raised = this_cpu_ptr(&raised_list);
189 lazy = this_cpu_ptr(&lazy_list);
190
191 if (llist_empty(raised) || arch_irq_work_has_interrupt())
192 if (llist_empty(lazy))
193 return false;
194
195 /* All work should have been flushed before going offline */
196 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
197
198 return true;
199}
200
201void irq_work_single(void *arg)
202{
203 struct irq_work *work = arg;
204 int flags;
205
206 /*
207 * Clear the PENDING bit, after this point the @work can be re-used.
208 * The PENDING bit acts as a lock, and we own it, so we can clear it
209 * without atomic ops.
210 */
211 flags = atomic_read(&work->node.a_flags);
212 flags &= ~IRQ_WORK_PENDING;
213 atomic_set(&work->node.a_flags, flags);
214
215 /*
216 * See irq_work_claim().
217 */
218 smp_mb();
219
220 lockdep_irq_work_enter(flags);
221 work->func(work);
222 lockdep_irq_work_exit(flags);
223
224 /*
225 * Clear the BUSY bit, if set, and return to the free state if no-one
226 * else claimed it meanwhile.
227 */
228 (void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY);
229
230 if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
231 !arch_irq_work_has_interrupt())
232 rcuwait_wake_up(&work->irqwait);
233}
234
235static void irq_work_run_list(struct llist_head *list)
236{
237 struct irq_work *work, *tmp;
238 struct llist_node *llnode;
239
240 /*
241 * On PREEMPT_RT IRQ-work which is not marked as HARD will be processed
242 * in a per-CPU thread in preemptible context. Only the items which are
243 * marked as IRQ_WORK_HARD_IRQ will be processed in hardirq context.
244 */
245 BUG_ON(!irqs_disabled() && !IS_ENABLED(CONFIG_PREEMPT_RT));
246
247 if (llist_empty(list))
248 return;
249
250 llnode = llist_del_all(list);
251 llist_for_each_entry_safe(work, tmp, llnode, node.llist)
252 irq_work_single(work);
253}
254
255/*
256 * hotplug calls this through:
257 * hotplug_cfd() -> flush_smp_call_function_queue()
258 */
259void irq_work_run(void)
260{
261 irq_work_run_list(this_cpu_ptr(&raised_list));
262 if (!IS_ENABLED(CONFIG_PREEMPT_RT))
263 irq_work_run_list(this_cpu_ptr(&lazy_list));
264 else
265 wake_irq_workd();
266}
267EXPORT_SYMBOL_GPL(irq_work_run);
268
269void irq_work_tick(void)
270{
271 struct llist_head *raised = this_cpu_ptr(&raised_list);
272
273 if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
274 irq_work_run_list(raised);
275
276 if (!IS_ENABLED(CONFIG_PREEMPT_RT))
277 irq_work_run_list(this_cpu_ptr(&lazy_list));
278 else
279 wake_irq_workd();
280}
281
282/*
283 * Synchronize against the irq_work @entry, ensures the entry is not
284 * currently in use.
285 */
286void irq_work_sync(struct irq_work *work)
287{
288 lockdep_assert_irqs_enabled();
289 might_sleep();
290
291 if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
292 !arch_irq_work_has_interrupt()) {
293 rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work),
294 TASK_UNINTERRUPTIBLE);
295 return;
296 }
297
298 while (irq_work_is_busy(work))
299 cpu_relax();
300}
301EXPORT_SYMBOL_GPL(irq_work_sync);
302
303static void run_irq_workd(unsigned int cpu)
304{
305 irq_work_run_list(this_cpu_ptr(&lazy_list));
306}
307
308static void irq_workd_setup(unsigned int cpu)
309{
310 sched_set_fifo_low(current);
311}
312
313static struct smp_hotplug_thread irqwork_threads = {
314 .store = &irq_workd,
315 .setup = irq_workd_setup,
316 .thread_should_run = irq_workd_should_run,
317 .thread_fn = run_irq_workd,
318 .thread_comm = "irq_work/%u",
319};
320
321static __init int irq_work_init_threads(void)
322{
323 if (IS_ENABLED(CONFIG_PREEMPT_RT))
324 BUG_ON(smpboot_register_percpu_thread(&irqwork_threads));
325 return 0;
326}
327early_initcall(irq_work_init_threads);