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
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
|
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/uaccess.h>
#include <litmus/ftdev.h>
#include <litmus/litmus.h>
#include <litmus/trace.h>
/******************************************************************************/
/* Allocation */
/******************************************************************************/
static struct ftdev overhead_dev;
#define trace_ts_buf overhead_dev.minor[0].buf
static unsigned int ts_seq_no = 0;
DEFINE_PER_CPU(atomic_t, irq_fired_count);
static inline void clear_irq_fired(void)
{
atomic_set(&__raw_get_cpu_var(irq_fired_count), 0);
}
static inline unsigned int get_and_clear_irq_fired(void)
{
/* This is potentially not atomic since we might migrate if
* preemptions are not disabled. As a tradeoff between
* accuracy and tracing overheads, this seems acceptable.
* If it proves to be a problem, then one could add a callback
* from the migration code to invalidate irq_fired_count.
*/
return atomic_xchg(&__raw_get_cpu_var(irq_fired_count), 0);
}
static inline void __save_irq_flags(struct timestamp *ts)
{
unsigned int irq_count;
irq_count = get_and_clear_irq_fired();
/* Store how many interrupts occurred. */
ts->irq_count = irq_count;
/* Extra flag because ts->irq_count overflows quickly. */
ts->irq_flag = irq_count > 0;
}
static inline void __save_timestamp_cpu(unsigned long event,
uint8_t type, uint8_t cpu,
uint16_t pid_fragment)
{
unsigned int seq_no;
struct timestamp *ts;
seq_no = fetch_and_inc((int *) &ts_seq_no);
if (ft_buffer_start_write(trace_ts_buf, (void**) &ts)) {
ts->event = event;
ts->seq_no = seq_no;
ts->pid = pid_fragment;
ts->cpu = cpu;
ts->task_type = type;
__save_irq_flags(ts);
barrier();
/* prevent re-ordering of ft_timestamp() */
ts->timestamp = ft_timestamp();
ft_buffer_finish_write(trace_ts_buf, ts);
}
}
static void __add_timestamp_user(struct timestamp *pre_recorded)
{
unsigned int seq_no;
struct timestamp *ts;
seq_no = fetch_and_inc((int *) &ts_seq_no);
if (ft_buffer_start_write(trace_ts_buf, (void**) &ts)) {
*ts = *pre_recorded;
ts->seq_no = seq_no;
__save_irq_flags(ts);
ft_buffer_finish_write(trace_ts_buf, ts);
}
}
static inline void __save_timestamp(unsigned long event,
uint8_t type)
{
__save_timestamp_cpu(event, type, raw_smp_processor_id(),
current->pid);
}
feather_callback void save_timestamp(unsigned long event)
{
__save_timestamp(event, TSK_UNKNOWN);
}
feather_callback void save_timestamp_def(unsigned long event,
unsigned long type)
{
__save_timestamp(event, (uint8_t) type);
}
feather_callback void save_timestamp_task(unsigned long event,
unsigned long t_ptr)
{
struct task_struct *t = (struct task_struct *) t_ptr;
int rt = is_realtime(t);
__save_timestamp_cpu(event, rt ? TSK_RT : TSK_BE,
raw_smp_processor_id(),
t->pid);
}
feather_callback void save_timestamp_cpu(unsigned long event,
unsigned long cpu)
{
__save_timestamp_cpu(event, TSK_UNKNOWN, cpu,
current->pid);
}
feather_callback void save_task_latency(unsigned long event,
unsigned long when_ptr)
{
lt_t now = litmus_clock();
lt_t *when = (lt_t*) when_ptr;
unsigned int seq_no;
int cpu = raw_smp_processor_id();
struct timestamp *ts;
seq_no = fetch_and_inc((int *) &ts_seq_no);
if (ft_buffer_start_write(trace_ts_buf, (void**) &ts)) {
ts->event = event;
ts->timestamp = now - *when;
ts->seq_no = seq_no;
ts->cpu = cpu;
ts->pid = 0;
ts->task_type = TSK_RT;
__save_irq_flags(ts);
ft_buffer_finish_write(trace_ts_buf, ts);
}
}
/******************************************************************************/
/* DEVICE FILE DRIVER */
/******************************************************************************/
/*
* should be 8M; it is the max we can ask to buddy system allocator (MAX_ORDER)
* and we might not get as much
*/
#define NO_TIMESTAMPS (2 << 16)
static int alloc_timestamp_buffer(struct ftdev* ftdev, unsigned int idx)
{
unsigned int count = NO_TIMESTAMPS;
/* An overhead-tracing timestamp should be exactly 16 bytes long. */
BUILD_BUG_ON(sizeof(struct timestamp) != 16);
while (count && !trace_ts_buf) {
printk("time stamp buffer: trying to allocate %u time stamps.\n", count);
ftdev->minor[idx].buf = alloc_ft_buffer(count, sizeof(struct timestamp));
count /= 2;
}
return ftdev->minor[idx].buf ? 0 : -ENOMEM;
}
static void free_timestamp_buffer(struct ftdev* ftdev, unsigned int idx)
{
free_ft_buffer(ftdev->minor[idx].buf);
ftdev->minor[idx].buf = NULL;
}
static ssize_t write_timestamp_from_user(struct ft_buffer* buf, size_t len,
const char __user *from)
{
ssize_t consumed = 0;
struct timestamp ts;
/* don't give us partial timestamps */
if (len % sizeof(ts))
return -EINVAL;
while (len >= sizeof(ts)) {
if (copy_from_user(&ts, from, sizeof(ts))) {
consumed = -EFAULT;
goto out;
}
len -= sizeof(ts);
from += sizeof(ts);
consumed += sizeof(ts);
__add_timestamp_user(&ts);
}
out:
return consumed;
}
static int __init init_ft_overhead_trace(void)
{
int err, cpu;
printk("Initializing Feather-Trace overhead tracing device.\n");
err = ftdev_init(&overhead_dev, THIS_MODULE, 1, "ft_trace");
if (err)
goto err_out;
overhead_dev.alloc = alloc_timestamp_buffer;
overhead_dev.free = free_timestamp_buffer;
overhead_dev.write = write_timestamp_from_user;
err = register_ftdev(&overhead_dev);
if (err)
goto err_dealloc;
/* initialize IRQ flags */
for (cpu = 0; cpu < NR_CPUS; cpu++) {
clear_irq_fired();
}
return 0;
err_dealloc:
ftdev_exit(&overhead_dev);
err_out:
printk(KERN_WARNING "Could not register ft_trace module.\n");
return err;
}
static void __exit exit_ft_overhead_trace(void)
{
ftdev_exit(&overhead_dev);
}
module_init(init_ft_overhead_trace);
module_exit(exit_ft_overhead_trace);
|
