1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
/*
* Functions related to softirq rq completions
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/sched.h>
#include "blk.h"
static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
/*
* Softirq action handler - move entries to local list and loop over them
* while passing them to the queue registered handler.
*/
static __latent_entropy void blk_done_softirq(struct softirq_action *h)
{
struct list_head *cpu_list, local_list;
local_irq_disable();
cpu_list = this_cpu_ptr(&blk_cpu_done);
list_replace_init(cpu_list, &local_list);
local_irq_enable();
while (!list_empty(&local_list)) {
struct request *rq;
rq = list_entry(local_list.next, struct request, ipi_list);
list_del_init(&rq->ipi_list);
rq->q->softirq_done_fn(rq);
}
}
#ifdef CONFIG_SMP
static void trigger_softirq(void *data)
{
struct request *rq = data;
unsigned long flags;
struct list_head *list;
local_irq_save(flags);
list = this_cpu_ptr(&blk_cpu_done);
list_add_tail(&rq->ipi_list, list);
if (list->next == &rq->ipi_list)
raise_softirq_irqoff(BLOCK_SOFTIRQ);
local_irq_restore(flags);
}
/*
* Setup and invoke a run of 'trigger_softirq' on the given cpu.
*/
static int raise_blk_irq(int cpu, struct request *rq)
{
if (cpu_online(cpu)) {
struct call_single_data *data = &rq->csd;
data->func = trigger_softirq;
data->info = rq;
data->flags = 0;
smp_call_function_single_async(cpu, data);
return 0;
}
return 1;
}
#else /* CONFIG_SMP */
static int raise_blk_irq(int cpu, struct request *rq)
{
return 1;
}
#endif
static int blk_softirq_cpu_dead(unsigned int cpu)
{
/*
* If a CPU goes away, splice its entries to the current CPU
* and trigger a run of the softirq
*/
local_irq_disable();
list_splice_init(&per_cpu(blk_cpu_done, cpu),
this_cpu_ptr(&blk_cpu_done));
raise_softirq_irqoff(BLOCK_SOFTIRQ);
local_irq_enable();
return 0;
}
void __blk_complete_request(struct request *req)
{
int ccpu, cpu;
struct request_queue *q = req->q;
unsigned long flags;
bool shared = false;
BUG_ON(!q->softirq_done_fn);
local_irq_save(flags);
cpu = smp_processor_id();
/*
* Select completion CPU
*/
if (req->cpu != -1) {
ccpu = req->cpu;
if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
shared = cpus_share_cache(cpu, ccpu);
} else
ccpu = cpu;
/*
* If current CPU and requested CPU share a cache, run the softirq on
* the current CPU. One might concern this is just like
* QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
* running in interrupt handler, and currently I/O controller doesn't
* support multiple interrupts, so current CPU is unique actually. This
* avoids IPI sending from current CPU to the first CPU of a group.
*/
if (ccpu == cpu || shared) {
struct list_head *list;
do_local:
list = this_cpu_ptr(&blk_cpu_done);
list_add_tail(&req->ipi_list, list);
/*
* if the list only contains our just added request,
* signal a raise of the softirq. If there are already
* entries there, someone already raised the irq but it
* hasn't run yet.
*/
if (list->next == &req->ipi_list)
raise_softirq_irqoff(BLOCK_SOFTIRQ);
} else if (raise_blk_irq(ccpu, req))
goto do_local;
local_irq_restore(flags);
}
/**
* blk_complete_request - end I/O on a request
* @req: the request being processed
*
* Description:
* Ends all I/O on a request. It does not handle partial completions,
* unless the driver actually implements this in its completion callback
* through requeueing. The actual completion happens out-of-order,
* through a softirq handler. The user must have registered a completion
* callback through blk_queue_softirq_done().
**/
void blk_complete_request(struct request *req)
{
if (unlikely(blk_should_fake_timeout(req->q)))
return;
if (!blk_mark_rq_complete(req))
__blk_complete_request(req);
}
EXPORT_SYMBOL(blk_complete_request);
static __init int blk_softirq_init(void)
{
int i;
for_each_possible_cpu(i)
INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
"block/softirq:dead", NULL,
blk_softirq_cpu_dead);
return 0;
}
subsys_initcall(blk_softirq_init);
|
