1b2441318SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0
2511cbce2SChristoph Hellwig /*
3511cbce2SChristoph Hellwig * Functions related to interrupt-poll handling in the block layer. This
4511cbce2SChristoph Hellwig * is similar to NAPI for network devices.
5511cbce2SChristoph Hellwig */
6511cbce2SChristoph Hellwig #include <linux/kernel.h>
7511cbce2SChristoph Hellwig #include <linux/module.h>
8511cbce2SChristoph Hellwig #include <linux/init.h>
9511cbce2SChristoph Hellwig #include <linux/bio.h>
10511cbce2SChristoph Hellwig #include <linux/interrupt.h>
11511cbce2SChristoph Hellwig #include <linux/cpu.h>
12511cbce2SChristoph Hellwig #include <linux/irq_poll.h>
13511cbce2SChristoph Hellwig #include <linux/delay.h>
14511cbce2SChristoph Hellwig
15511cbce2SChristoph Hellwig static unsigned int irq_poll_budget __read_mostly = 256;
16511cbce2SChristoph Hellwig
17511cbce2SChristoph Hellwig static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);
18511cbce2SChristoph Hellwig
19511cbce2SChristoph Hellwig /**
20511cbce2SChristoph Hellwig * irq_poll_sched - Schedule a run of the iopoll handler
21511cbce2SChristoph Hellwig * @iop: The parent iopoll structure
22511cbce2SChristoph Hellwig *
23511cbce2SChristoph Hellwig * Description:
24511cbce2SChristoph Hellwig * Add this irq_poll structure to the pending poll list and trigger the
25ea51190cSChristoph Hellwig * raise of the blk iopoll softirq.
26511cbce2SChristoph Hellwig **/
irq_poll_sched(struct irq_poll * iop)27511cbce2SChristoph Hellwig void irq_poll_sched(struct irq_poll *iop)
28511cbce2SChristoph Hellwig {
29511cbce2SChristoph Hellwig unsigned long flags;
30511cbce2SChristoph Hellwig
31ea51190cSChristoph Hellwig if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
32ea51190cSChristoph Hellwig return;
332ee177e9SBart Van Assche if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
34ea51190cSChristoph Hellwig return;
35ea51190cSChristoph Hellwig
36511cbce2SChristoph Hellwig local_irq_save(flags);
37511cbce2SChristoph Hellwig list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
384133b013SSteve Wise raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
39511cbce2SChristoph Hellwig local_irq_restore(flags);
40511cbce2SChristoph Hellwig }
41511cbce2SChristoph Hellwig EXPORT_SYMBOL(irq_poll_sched);
42511cbce2SChristoph Hellwig
43511cbce2SChristoph Hellwig /**
44511cbce2SChristoph Hellwig * __irq_poll_complete - Mark this @iop as un-polled again
45511cbce2SChristoph Hellwig * @iop: The parent iopoll structure
46511cbce2SChristoph Hellwig *
47511cbce2SChristoph Hellwig * Description:
48511cbce2SChristoph Hellwig * See irq_poll_complete(). This function must be called with interrupts
49511cbce2SChristoph Hellwig * disabled.
50511cbce2SChristoph Hellwig **/
__irq_poll_complete(struct irq_poll * iop)5183af187dSChristoph Hellwig static void __irq_poll_complete(struct irq_poll *iop)
52511cbce2SChristoph Hellwig {
53511cbce2SChristoph Hellwig list_del(&iop->list);
54511cbce2SChristoph Hellwig smp_mb__before_atomic();
55511cbce2SChristoph Hellwig clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
56511cbce2SChristoph Hellwig }
57511cbce2SChristoph Hellwig
58511cbce2SChristoph Hellwig /**
59511cbce2SChristoph Hellwig * irq_poll_complete - Mark this @iop as un-polled again
60511cbce2SChristoph Hellwig * @iop: The parent iopoll structure
61511cbce2SChristoph Hellwig *
62511cbce2SChristoph Hellwig * Description:
63511cbce2SChristoph Hellwig * If a driver consumes less than the assigned budget in its run of the
64511cbce2SChristoph Hellwig * iopoll handler, it'll end the polled mode by calling this function. The
65ea51190cSChristoph Hellwig * iopoll handler will not be invoked again before irq_poll_sched()
66511cbce2SChristoph Hellwig * is called.
67511cbce2SChristoph Hellwig **/
irq_poll_complete(struct irq_poll * iop)68511cbce2SChristoph Hellwig void irq_poll_complete(struct irq_poll *iop)
69511cbce2SChristoph Hellwig {
70511cbce2SChristoph Hellwig unsigned long flags;
71511cbce2SChristoph Hellwig
72511cbce2SChristoph Hellwig local_irq_save(flags);
73511cbce2SChristoph Hellwig __irq_poll_complete(iop);
74511cbce2SChristoph Hellwig local_irq_restore(flags);
75511cbce2SChristoph Hellwig }
76511cbce2SChristoph Hellwig EXPORT_SYMBOL(irq_poll_complete);
77511cbce2SChristoph Hellwig
irq_poll_softirq(struct softirq_action * h)780766f788SEmese Revfy static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
79511cbce2SChristoph Hellwig {
80511cbce2SChristoph Hellwig struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);
81511cbce2SChristoph Hellwig int rearm = 0, budget = irq_poll_budget;
82511cbce2SChristoph Hellwig unsigned long start_time = jiffies;
83511cbce2SChristoph Hellwig
84511cbce2SChristoph Hellwig local_irq_disable();
85511cbce2SChristoph Hellwig
86511cbce2SChristoph Hellwig while (!list_empty(list)) {
87511cbce2SChristoph Hellwig struct irq_poll *iop;
88511cbce2SChristoph Hellwig int work, weight;
89511cbce2SChristoph Hellwig
90511cbce2SChristoph Hellwig /*
91511cbce2SChristoph Hellwig * If softirq window is exhausted then punt.
92511cbce2SChristoph Hellwig */
93511cbce2SChristoph Hellwig if (budget <= 0 || time_after(jiffies, start_time)) {
94511cbce2SChristoph Hellwig rearm = 1;
95511cbce2SChristoph Hellwig break;
96511cbce2SChristoph Hellwig }
97511cbce2SChristoph Hellwig
98511cbce2SChristoph Hellwig local_irq_enable();
99511cbce2SChristoph Hellwig
100511cbce2SChristoph Hellwig /* Even though interrupts have been re-enabled, this
101511cbce2SChristoph Hellwig * access is safe because interrupts can only add new
102511cbce2SChristoph Hellwig * entries to the tail of this list, and only ->poll()
103511cbce2SChristoph Hellwig * calls can remove this head entry from the list.
104511cbce2SChristoph Hellwig */
105511cbce2SChristoph Hellwig iop = list_entry(list->next, struct irq_poll, list);
106511cbce2SChristoph Hellwig
107511cbce2SChristoph Hellwig weight = iop->weight;
108511cbce2SChristoph Hellwig work = 0;
109511cbce2SChristoph Hellwig if (test_bit(IRQ_POLL_F_SCHED, &iop->state))
110511cbce2SChristoph Hellwig work = iop->poll(iop, weight);
111511cbce2SChristoph Hellwig
112511cbce2SChristoph Hellwig budget -= work;
113511cbce2SChristoph Hellwig
114511cbce2SChristoph Hellwig local_irq_disable();
115511cbce2SChristoph Hellwig
116511cbce2SChristoph Hellwig /*
117511cbce2SChristoph Hellwig * Drivers must not modify the iopoll state, if they
118511cbce2SChristoph Hellwig * consume their assigned weight (or more, some drivers can't
119511cbce2SChristoph Hellwig * easily just stop processing, they have to complete an
120511cbce2SChristoph Hellwig * entire mask of commands).In such cases this code
121511cbce2SChristoph Hellwig * still "owns" the iopoll instance and therefore can
122511cbce2SChristoph Hellwig * move the instance around on the list at-will.
123511cbce2SChristoph Hellwig */
124511cbce2SChristoph Hellwig if (work >= weight) {
1250bc92aceSChristoph Hellwig if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
126511cbce2SChristoph Hellwig __irq_poll_complete(iop);
127511cbce2SChristoph Hellwig else
128511cbce2SChristoph Hellwig list_move_tail(&iop->list, list);
129511cbce2SChristoph Hellwig }
130511cbce2SChristoph Hellwig }
131511cbce2SChristoph Hellwig
132511cbce2SChristoph Hellwig if (rearm)
133511cbce2SChristoph Hellwig __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
134511cbce2SChristoph Hellwig
135511cbce2SChristoph Hellwig local_irq_enable();
136511cbce2SChristoph Hellwig }
137511cbce2SChristoph Hellwig
138511cbce2SChristoph Hellwig /**
139511cbce2SChristoph Hellwig * irq_poll_disable - Disable iopoll on this @iop
140511cbce2SChristoph Hellwig * @iop: The parent iopoll structure
141511cbce2SChristoph Hellwig *
142511cbce2SChristoph Hellwig * Description:
143511cbce2SChristoph Hellwig * Disable io polling and wait for any pending callbacks to have completed.
144511cbce2SChristoph Hellwig **/
irq_poll_disable(struct irq_poll * iop)145511cbce2SChristoph Hellwig void irq_poll_disable(struct irq_poll *iop)
146511cbce2SChristoph Hellwig {
147511cbce2SChristoph Hellwig set_bit(IRQ_POLL_F_DISABLE, &iop->state);
148511cbce2SChristoph Hellwig while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
149511cbce2SChristoph Hellwig msleep(1);
150511cbce2SChristoph Hellwig clear_bit(IRQ_POLL_F_DISABLE, &iop->state);
151511cbce2SChristoph Hellwig }
152511cbce2SChristoph Hellwig EXPORT_SYMBOL(irq_poll_disable);
153511cbce2SChristoph Hellwig
154511cbce2SChristoph Hellwig /**
155511cbce2SChristoph Hellwig * irq_poll_enable - Enable iopoll on this @iop
156511cbce2SChristoph Hellwig * @iop: The parent iopoll structure
157511cbce2SChristoph Hellwig *
158511cbce2SChristoph Hellwig * Description:
159511cbce2SChristoph Hellwig * Enable iopoll on this @iop. Note that the handler run will not be
160511cbce2SChristoph Hellwig * scheduled, it will only mark it as active.
161511cbce2SChristoph Hellwig **/
irq_poll_enable(struct irq_poll * iop)162511cbce2SChristoph Hellwig void irq_poll_enable(struct irq_poll *iop)
163511cbce2SChristoph Hellwig {
164511cbce2SChristoph Hellwig BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state));
165511cbce2SChristoph Hellwig smp_mb__before_atomic();
166511cbce2SChristoph Hellwig clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
167511cbce2SChristoph Hellwig }
168511cbce2SChristoph Hellwig EXPORT_SYMBOL(irq_poll_enable);
169511cbce2SChristoph Hellwig
170511cbce2SChristoph Hellwig /**
171511cbce2SChristoph Hellwig * irq_poll_init - Initialize this @iop
172511cbce2SChristoph Hellwig * @iop: The parent iopoll structure
173511cbce2SChristoph Hellwig * @weight: The default weight (or command completion budget)
174511cbce2SChristoph Hellwig * @poll_fn: The handler to invoke
175511cbce2SChristoph Hellwig *
176511cbce2SChristoph Hellwig * Description:
17778d0264eSChristoph Hellwig * Initialize and enable this irq_poll structure.
178511cbce2SChristoph Hellwig **/
irq_poll_init(struct irq_poll * iop,int weight,irq_poll_fn * poll_fn)179511cbce2SChristoph Hellwig void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn)
180511cbce2SChristoph Hellwig {
181511cbce2SChristoph Hellwig memset(iop, 0, sizeof(*iop));
182511cbce2SChristoph Hellwig INIT_LIST_HEAD(&iop->list);
183511cbce2SChristoph Hellwig iop->weight = weight;
184511cbce2SChristoph Hellwig iop->poll = poll_fn;
185511cbce2SChristoph Hellwig }
186511cbce2SChristoph Hellwig EXPORT_SYMBOL(irq_poll_init);
187511cbce2SChristoph Hellwig
irq_poll_cpu_dead(unsigned int cpu)18875e12ed6SSebastian Andrzej Siewior static int irq_poll_cpu_dead(unsigned int cpu)
189511cbce2SChristoph Hellwig {
190511cbce2SChristoph Hellwig /*
191*75d8cce1SSebastian Andrzej Siewior * If a CPU goes away, splice its entries to the current CPU and
192*75d8cce1SSebastian Andrzej Siewior * set the POLL softirq bit. The local_bh_disable()/enable() pair
193*75d8cce1SSebastian Andrzej Siewior * ensures that it is handled. Otherwise the current CPU could
194*75d8cce1SSebastian Andrzej Siewior * reach idle with the POLL softirq pending.
195511cbce2SChristoph Hellwig */
196*75d8cce1SSebastian Andrzej Siewior local_bh_disable();
197511cbce2SChristoph Hellwig local_irq_disable();
198511cbce2SChristoph Hellwig list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
199511cbce2SChristoph Hellwig this_cpu_ptr(&blk_cpu_iopoll));
200511cbce2SChristoph Hellwig __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
201511cbce2SChristoph Hellwig local_irq_enable();
202*75d8cce1SSebastian Andrzej Siewior local_bh_enable();
203511cbce2SChristoph Hellwig
20475e12ed6SSebastian Andrzej Siewior return 0;
205511cbce2SChristoph Hellwig }
206511cbce2SChristoph Hellwig
irq_poll_setup(void)207511cbce2SChristoph Hellwig static __init int irq_poll_setup(void)
208511cbce2SChristoph Hellwig {
209511cbce2SChristoph Hellwig int i;
210511cbce2SChristoph Hellwig
211511cbce2SChristoph Hellwig for_each_possible_cpu(i)
212511cbce2SChristoph Hellwig INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));
213511cbce2SChristoph Hellwig
214511cbce2SChristoph Hellwig open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq);
21575e12ed6SSebastian Andrzej Siewior cpuhp_setup_state_nocalls(CPUHP_IRQ_POLL_DEAD, "irq_poll:dead", NULL,
21675e12ed6SSebastian Andrzej Siewior irq_poll_cpu_dead);
217511cbce2SChristoph Hellwig return 0;
218511cbce2SChristoph Hellwig }
219511cbce2SChristoph Hellwig subsys_initcall(irq_poll_setup);
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