summaryrefslogtreecommitdiff
path: root/kernel/trace/trace_irqsoff.c
blob: a9131b0cf1a57d133acb1d7ee3c677823f4366c5 (plain)
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
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
/*
 * trace irqs off criticall timings
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 * From code in the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/fs.h>

#include "trace.h"

static struct trace_array		*irqsoff_trace __read_mostly;
static int				tracer_enabled __read_mostly;

/*
 * Sequence count - we record it when starting a measurement and
 * skip the latency if the sequence has changed - some other section
 * did a maximum and could disturb our measurement with serial console
 * printouts, etc. Truly coinciding maximum latencies should be rare
 * and what happens together happens separately as well, so this doesnt
 * decrease the validity of the maximum found:
 */
static __cacheline_aligned_in_smp	unsigned long max_sequence;

#ifdef CONFIG_FTRACE
/*
 * irqsoff uses its own tracer function to keep the overhead down:
 */
static void notrace
irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;
	long disabled;
	int cpu;

	if (likely(!tracer_enabled))
		return;

	local_save_flags(flags);

	if (!irqs_disabled_flags(flags))
		return;

	cpu = raw_smp_processor_id();
	data = tr->data[cpu];
	disabled = atomic_inc_return(&data->disabled);

	if (likely(disabled == 1))
		ftrace(tr, data, ip, parent_ip, flags);

	atomic_dec(&data->disabled);
}

static struct ftrace_ops trace_ops __read_mostly =
{
	.func = irqsoff_tracer_call,
};
#endif /* CONFIG_FTRACE */

/*
 * Should this new latency be reported/recorded?
 */
static int notrace report_latency(cycle_t delta)
{
	if (tracing_thresh) {
		if (delta < tracing_thresh)
			return 0;
	} else {
		if (delta <= tracing_max_latency)
			return 0;
	}
	return 1;
}

static void notrace
check_critical_timing(struct trace_array *tr,
		      struct trace_array_cpu *data,
		      unsigned long parent_ip,
		      int cpu)
{
	unsigned long latency, t0, t1;
	cycle_t T0, T1, T2, delta;
	unsigned long flags;

	/*
	 * usecs conversion is slow so we try to delay the conversion
	 * as long as possible:
	 */
	T0 = data->preempt_timestamp;
	T1 = now(cpu);
	delta = T1-T0;

	local_save_flags(flags);

	if (!report_latency(delta))
		goto out;

	ftrace(tr, data, CALLER_ADDR0, parent_ip, flags);
	/*
	 * Update the timestamp, because the trace entry above
	 * might change it (it can only get larger so the latency
	 * is fair to be reported):
	 */
	T2 = now(cpu);

	delta = T2-T0;

	latency = nsecs_to_usecs(delta);

	if (data->critical_sequence != max_sequence)
		goto out;

	tracing_max_latency = delta;
	t0 = nsecs_to_usecs(T0);
	t1 = nsecs_to_usecs(T1);

	data->critical_end = parent_ip;

	update_max_tr_single(tr, current, cpu);

	if (tracing_thresh)
		printk(KERN_INFO "(%16s-%-5d|#%d): %lu us critical section "
		       "violates %lu us threshold.\n"
		       " => started at timestamp %lu: ",
				current->comm, current->pid,
				raw_smp_processor_id(),
				latency, nsecs_to_usecs(tracing_thresh), t0);
	else
		printk(KERN_INFO "(%16s-%-5d|#%d):"
		       " new %lu us maximum-latency "
		       "critical section.\n => started at timestamp %lu: ",
				current->comm, current->pid,
				raw_smp_processor_id(),
				latency, t0);

	print_symbol(KERN_CONT "<%s>\n", data->critical_start);
	printk(KERN_CONT " =>   ended at timestamp %lu: ", t1);
	print_symbol(KERN_CONT "<%s>\n", data->critical_end);
	dump_stack();
	t1 = nsecs_to_usecs(now(cpu));
	printk(KERN_CONT " =>   dump-end timestamp %lu\n\n", t1);

	max_sequence++;

out:
	data->critical_sequence = max_sequence;
	data->preempt_timestamp = now(cpu);
	tracing_reset(data);
	ftrace(tr, data, CALLER_ADDR0, parent_ip, flags);
}

static inline void notrace
start_critical_timing(unsigned long ip, unsigned long parent_ip)
{
	int cpu;
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;

	if (likely(!tracer_enabled))
		return;

	cpu = raw_smp_processor_id();
	data = tr->data[cpu];

	if (unlikely(!data) || unlikely(!data->trace) ||
	    data->critical_start || atomic_read(&data->disabled))
		return;

	atomic_inc(&data->disabled);

	data->critical_sequence = max_sequence;
	data->preempt_timestamp = now(cpu);
	data->critical_start = parent_ip;
	tracing_reset(data);

	local_save_flags(flags);
	ftrace(tr, data, ip, parent_ip, flags);

	atomic_dec(&data->disabled);
}

static inline void notrace
stop_critical_timing(unsigned long ip, unsigned long parent_ip)
{
	int cpu;
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;

	if (likely(!tracer_enabled))
		return;

	cpu = raw_smp_processor_id();
	data = tr->data[cpu];

	if (unlikely(!data) || unlikely(!data->trace) ||
	    !data->critical_start || atomic_read(&data->disabled))
		return;

	atomic_inc(&data->disabled);
	local_save_flags(flags);
	ftrace(tr, data, ip, parent_ip, flags);
	check_critical_timing(tr, data, parent_ip, cpu);
	data->critical_start = 0;
	atomic_dec(&data->disabled);
}

void notrace start_critical_timings(void)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}

void notrace stop_critical_timings(void)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}

#ifdef CONFIG_PROVE_LOCKING
void notrace time_hardirqs_on(unsigned long a0, unsigned long a1)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		stop_critical_timing(a0, a1);
}

void notrace time_hardirqs_off(unsigned long a0, unsigned long a1)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		start_critical_timing(a0, a1);
}

#else /* !CONFIG_PROVE_LOCKING */

/*
 * Stubs:
 */

void early_boot_irqs_off(void)
{
}

void early_boot_irqs_on(void)
{
}

void trace_softirqs_on(unsigned long ip)
{
}

void trace_softirqs_off(unsigned long ip)
{
}

inline void print_irqtrace_events(struct task_struct *curr)
{
}

/*
 * We are only interested in hardirq on/off events:
 */
void notrace trace_hardirqs_on(void)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_on);

void notrace trace_hardirqs_off(void)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_off);

void notrace trace_hardirqs_on_caller(unsigned long caller_addr)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		stop_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_on_caller);

void notrace trace_hardirqs_off_caller(unsigned long caller_addr)
{
	unsigned long flags;

	local_save_flags(flags);

	if (irqs_disabled_flags(flags))
		start_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_off_caller);

#endif /* CONFIG_PROVE_LOCKING */

static void start_irqsoff_tracer(struct trace_array *tr)
{
	tracer_enabled = 1;
	register_ftrace_function(&trace_ops);
}

static void stop_irqsoff_tracer(struct trace_array *tr)
{
	unregister_ftrace_function(&trace_ops);
	tracer_enabled = 0;
}

static void irqsoff_tracer_init(struct trace_array *tr)
{
	irqsoff_trace = tr;
	/* make sure that the tracer is visibel */
	smp_wmb();

	if (tr->ctrl)
		start_irqsoff_tracer(tr);
}

static void irqsoff_tracer_reset(struct trace_array *tr)
{
	if (tr->ctrl)
		stop_irqsoff_tracer(tr);
}

static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
{
	if (tr->ctrl)
		start_irqsoff_tracer(tr);
	else
		stop_irqsoff_tracer(tr);
}

static void notrace irqsoff_tracer_open(struct trace_iterator *iter)
{
	/* stop the trace while dumping */
	if (iter->tr->ctrl)
		stop_irqsoff_tracer(iter->tr);
}

static void notrace irqsoff_tracer_close(struct trace_iterator *iter)
{
	if (iter->tr->ctrl)
		start_irqsoff_tracer(iter->tr);
}

static struct tracer irqsoff_tracer __read_mostly =
{
	.name		= "irqsoff",
	.init		= irqsoff_tracer_init,
	.reset		= irqsoff_tracer_reset,
	.open		= irqsoff_tracer_open,
	.close		= irqsoff_tracer_close,
	.ctrl_update	= irqsoff_tracer_ctrl_update,
	.print_max	= 1,
};

__init static int init_irqsoff_tracer(void)
{
	register_tracer(&irqsoff_tracer);

	return 0;
}
device_initcall(init_irqsoff_tracer);