1 // SPDX-License-Identifier: GPL-2.0
3 * Functions related to softirq rq completions
5 #include <linux/kernel.h>
6 #include <linux/module.h>
7 #include <linux/init.h>
9 #include <linux/blkdev.h>
10 #include <linux/interrupt.h>
11 #include <linux/cpu.h>
12 #include <linux/sched.h>
13 #include <linux/sched/topology.h>
17 static DEFINE_PER_CPU(struct list_head
, blk_cpu_done
);
20 * Softirq action handler - move entries to local list and loop over them
21 * while passing them to the queue registered handler.
23 static __latent_entropy
void blk_done_softirq(struct softirq_action
*h
)
25 struct list_head
*cpu_list
, local_list
;
28 cpu_list
= this_cpu_ptr(&blk_cpu_done
);
29 list_replace_init(cpu_list
, &local_list
);
32 while (!list_empty(&local_list
)) {
35 rq
= list_entry(local_list
.next
, struct request
, ipi_list
);
36 list_del_init(&rq
->ipi_list
);
37 rq
->q
->softirq_done_fn(rq
);
42 static void trigger_softirq(void *data
)
44 struct request
*rq
= data
;
46 struct list_head
*list
;
48 local_irq_save(flags
);
49 list
= this_cpu_ptr(&blk_cpu_done
);
50 list_add_tail(&rq
->ipi_list
, list
);
52 if (list
->next
== &rq
->ipi_list
)
53 raise_softirq_irqoff(BLOCK_SOFTIRQ
);
55 local_irq_restore(flags
);
59 * Setup and invoke a run of 'trigger_softirq' on the given cpu.
61 static int raise_blk_irq(int cpu
, struct request
*rq
)
63 if (cpu_online(cpu
)) {
64 call_single_data_t
*data
= &rq
->csd
;
66 data
->func
= trigger_softirq
;
70 smp_call_function_single_async(cpu
, data
);
76 #else /* CONFIG_SMP */
77 static int raise_blk_irq(int cpu
, struct request
*rq
)
83 static int blk_softirq_cpu_dead(unsigned int cpu
)
86 * If a CPU goes away, splice its entries to the current CPU
87 * and trigger a run of the softirq
90 list_splice_init(&per_cpu(blk_cpu_done
, cpu
),
91 this_cpu_ptr(&blk_cpu_done
));
92 raise_softirq_irqoff(BLOCK_SOFTIRQ
);
98 void __blk_complete_request(struct request
*req
)
101 struct request_queue
*q
= req
->q
;
105 BUG_ON(!q
->softirq_done_fn
);
107 local_irq_save(flags
);
108 cpu
= smp_processor_id();
111 * Select completion CPU
113 if (req
->cpu
!= -1) {
115 if (!test_bit(QUEUE_FLAG_SAME_FORCE
, &q
->queue_flags
))
116 shared
= cpus_share_cache(cpu
, ccpu
);
121 * If current CPU and requested CPU share a cache, run the softirq on
122 * the current CPU. One might concern this is just like
123 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
124 * running in interrupt handler, and currently I/O controller doesn't
125 * support multiple interrupts, so current CPU is unique actually. This
126 * avoids IPI sending from current CPU to the first CPU of a group.
128 if (ccpu
== cpu
|| shared
) {
129 struct list_head
*list
;
131 list
= this_cpu_ptr(&blk_cpu_done
);
132 list_add_tail(&req
->ipi_list
, list
);
135 * if the list only contains our just added request,
136 * signal a raise of the softirq. If there are already
137 * entries there, someone already raised the irq but it
140 if (list
->next
== &req
->ipi_list
)
141 raise_softirq_irqoff(BLOCK_SOFTIRQ
);
142 } else if (raise_blk_irq(ccpu
, req
))
145 local_irq_restore(flags
);
149 * blk_complete_request - end I/O on a request
150 * @req: the request being processed
153 * Ends all I/O on a request. It does not handle partial completions,
154 * unless the driver actually implements this in its completion callback
155 * through requeueing. The actual completion happens out-of-order,
156 * through a softirq handler. The user must have registered a completion
157 * callback through blk_queue_softirq_done().
159 void blk_complete_request(struct request
*req
)
161 if (unlikely(blk_should_fake_timeout(req
->q
)))
163 if (!blk_mark_rq_complete(req
))
164 __blk_complete_request(req
);
166 EXPORT_SYMBOL(blk_complete_request
);
168 static __init
int blk_softirq_init(void)
172 for_each_possible_cpu(i
)
173 INIT_LIST_HEAD(&per_cpu(blk_cpu_done
, i
));
175 open_softirq(BLOCK_SOFTIRQ
, blk_done_softirq
);
176 cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD
,
177 "block/softirq:dead", NULL
,
178 blk_softirq_cpu_dead
);
181 subsys_initcall(blk_softirq_init
);