Line data Source code
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 :
27 : static DEFINE_PER_CPU(struct llist_head, raised_list);
28 : static DEFINE_PER_CPU(struct llist_head, lazy_list);
29 : static DEFINE_PER_CPU(struct task_struct *, irq_workd);
30 :
31 : static 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
40 : static void irq_work_wake(struct irq_work *entry)
41 : {
42 : wake_irq_workd();
43 : }
44 :
45 : static DEFINE_PER_CPU(struct irq_work, irq_work_wakeup) =
46 : IRQ_WORK_INIT_HARD(irq_work_wake);
47 : #endif
48 :
49 : static 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 : */
57 : static bool irq_work_claim(struct irq_work *work)
58 : {
59 : int oflags;
60 :
61 0 : 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 0 : if (oflags & IRQ_WORK_PENDING)
68 : return false;
69 : return true;
70 : }
71 :
72 0 : void __weak arch_irq_work_raise(void)
73 : {
74 : /*
75 : * Lame architectures will get the timer tick callback
76 : */
77 0 : }
78 :
79 : static __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 0 : arch_irq_work_raise();
85 : }
86 :
87 : /* Enqueue on current CPU, work must already be claimed and preempt disabled */
88 0 : static void __irq_work_queue_local(struct irq_work *work)
89 : {
90 : struct llist_head *list;
91 0 : bool rt_lazy_work = false;
92 0 : bool lazy_work = false;
93 : int work_flags;
94 :
95 0 : work_flags = atomic_read(&work->node.a_flags);
96 0 : if (work_flags & IRQ_WORK_LAZY)
97 0 : 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 0 : if (lazy_work || rt_lazy_work)
103 : list = this_cpu_ptr(&lazy_list);
104 : else
105 0 : list = this_cpu_ptr(&raised_list);
106 :
107 0 : if (!llist_add(&work->node.llist, list))
108 : return;
109 :
110 : /* If the work is "lazy", handle it from next tick if any */
111 0 : if (!lazy_work || tick_nohz_tick_stopped())
112 : irq_work_raise(work);
113 : }
114 :
115 : /* Enqueue the irq work @work on the current CPU */
116 0 : bool irq_work_queue(struct irq_work *work)
117 : {
118 : /* Only queue if not already pending */
119 0 : if (!irq_work_claim(work))
120 : return false;
121 :
122 : /* Queue the entry and raise the IPI if needed. */
123 0 : preempt_disable();
124 0 : __irq_work_queue_local(work);
125 0 : preempt_enable();
126 :
127 0 : return true;
128 : }
129 : EXPORT_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 : */
137 0 : bool irq_work_queue_on(struct irq_work *work, int cpu)
138 : {
139 : #ifndef CONFIG_SMP
140 0 : 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 : }
177 : out:
178 : preempt_enable();
179 :
180 : return true;
181 : #endif /* CONFIG_SMP */
182 : }
183 :
184 0 : bool irq_work_needs_cpu(void)
185 : {
186 : struct llist_head *raised, *lazy;
187 :
188 0 : raised = this_cpu_ptr(&raised_list);
189 0 : lazy = this_cpu_ptr(&lazy_list);
190 :
191 : if (llist_empty(raised) || arch_irq_work_has_interrupt())
192 0 : 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 :
201 0 : void irq_work_single(void *arg)
202 : {
203 0 : 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 0 : flags = atomic_read(&work->node.a_flags);
212 0 : flags &= ~IRQ_WORK_PENDING;
213 0 : atomic_set(&work->node.a_flags, flags);
214 :
215 : /*
216 : * See irq_work_claim().
217 : */
218 0 : smp_mb();
219 :
220 : lockdep_irq_work_enter(flags);
221 0 : 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 0 : (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 0 : rcuwait_wake_up(&work->irqwait);
233 0 : }
234 :
235 2943 : static 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 2943 : BUG_ON(!irqs_disabled() && !IS_ENABLED(CONFIG_PREEMPT_RT));
246 :
247 2943 : if (llist_empty(list))
248 : return;
249 :
250 0 : llnode = llist_del_all(list);
251 0 : llist_for_each_entry_safe(work, tmp, llnode, node.llist)
252 0 : irq_work_single(work);
253 : }
254 :
255 : /*
256 : * hotplug calls this through:
257 : * hotplug_cfd() -> flush_smp_call_function_queue()
258 : */
259 0 : void irq_work_run(void)
260 : {
261 0 : irq_work_run_list(this_cpu_ptr(&raised_list));
262 : if (!IS_ENABLED(CONFIG_PREEMPT_RT))
263 0 : irq_work_run_list(this_cpu_ptr(&lazy_list));
264 : else
265 : wake_irq_workd();
266 0 : }
267 : EXPORT_SYMBOL_GPL(irq_work_run);
268 :
269 2943 : void irq_work_tick(void)
270 : {
271 2943 : struct llist_head *raised = this_cpu_ptr(&raised_list);
272 :
273 2943 : if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
274 0 : irq_work_run_list(raised);
275 :
276 : if (!IS_ENABLED(CONFIG_PREEMPT_RT))
277 2943 : irq_work_run_list(this_cpu_ptr(&lazy_list));
278 : else
279 : wake_irq_workd();
280 2943 : }
281 :
282 : /*
283 : * Synchronize against the irq_work @entry, ensures the entry is not
284 : * currently in use.
285 : */
286 0 : void 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 0 : 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 : }
301 : EXPORT_SYMBOL_GPL(irq_work_sync);
302 :
303 : static void run_irq_workd(unsigned int cpu)
304 : {
305 : irq_work_run_list(this_cpu_ptr(&lazy_list));
306 : }
307 :
308 : static void irq_workd_setup(unsigned int cpu)
309 : {
310 : sched_set_fifo_low(current);
311 : }
312 :
313 : static 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 :
321 1 : static __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 1 : return 0;
326 : }
327 : early_initcall(irq_work_init_threads);
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