tracing/branch-tracer: fix a trace recursion on branch tracer
[linux-2.6] / kernel / trace / trace_branch.c
1 /*
2  * unlikely profiler
3  *
4  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5  */
6 #include <linux/kallsyms.h>
7 #include <linux/seq_file.h>
8 #include <linux/spinlock.h>
9 #include <linux/debugfs.h>
10 #include <linux/uaccess.h>
11 #include <linux/module.h>
12 #include <linux/ftrace.h>
13 #include <linux/hash.h>
14 #include <linux/fs.h>
15 #include <asm/local.h>
16 #include "trace.h"
17
18 #ifdef CONFIG_BRANCH_TRACER
19
20 static int branch_tracing_enabled __read_mostly;
21 static DEFINE_MUTEX(branch_tracing_mutex);
22 static struct trace_array *branch_tracer;
23
24 static void
25 probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
26 {
27         struct trace_array *tr = branch_tracer;
28         struct ring_buffer_event *event;
29         struct trace_branch *entry;
30         unsigned long flags, irq_flags;
31         int cpu, pc;
32         const char *p;
33
34         /*
35          * I would love to save just the ftrace_likely_data pointer, but
36          * this code can also be used by modules. Ugly things can happen
37          * if the module is unloaded, and then we go and read the
38          * pointer.  This is slower, but much safer.
39          */
40
41         if (unlikely(!tr))
42                 return;
43
44         raw_local_irq_save(flags);
45         cpu = raw_smp_processor_id();
46         if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
47                 goto out;
48
49         event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
50                                          &irq_flags);
51         if (!event)
52                 goto out;
53
54         pc = preempt_count();
55         entry   = ring_buffer_event_data(event);
56         tracing_generic_entry_update(&entry->ent, flags, pc);
57         entry->ent.type         = TRACE_BRANCH;
58
59         /* Strip off the path, only save the file */
60         p = f->file + strlen(f->file);
61         while (p >= f->file && *p != '/')
62                 p--;
63         p++;
64
65         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
66         strncpy(entry->file, p, TRACE_FILE_SIZE);
67         entry->func[TRACE_FUNC_SIZE] = 0;
68         entry->file[TRACE_FILE_SIZE] = 0;
69         entry->line = f->line;
70         entry->correct = val == expect;
71
72         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
73
74  out:
75         atomic_dec(&tr->data[cpu]->disabled);
76         raw_local_irq_restore(flags);
77 }
78
79 static inline
80 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
81 {
82         if (!branch_tracing_enabled)
83                 return;
84
85         probe_likely_condition(f, val, expect);
86 }
87
88 int enable_branch_tracing(struct trace_array *tr)
89 {
90         int ret = 0;
91
92         mutex_lock(&branch_tracing_mutex);
93         branch_tracer = tr;
94         /*
95          * Must be seen before enabling. The reader is a condition
96          * where we do not need a matching rmb()
97          */
98         smp_wmb();
99         branch_tracing_enabled++;
100         mutex_unlock(&branch_tracing_mutex);
101
102         return ret;
103 }
104
105 void disable_branch_tracing(void)
106 {
107         mutex_lock(&branch_tracing_mutex);
108
109         if (!branch_tracing_enabled)
110                 goto out_unlock;
111
112         branch_tracing_enabled--;
113
114  out_unlock:
115         mutex_unlock(&branch_tracing_mutex);
116 }
117
118 static void start_branch_trace(struct trace_array *tr)
119 {
120         enable_branch_tracing(tr);
121 }
122
123 static void stop_branch_trace(struct trace_array *tr)
124 {
125         disable_branch_tracing();
126 }
127
128 static void branch_trace_init(struct trace_array *tr)
129 {
130         int cpu;
131
132         for_each_online_cpu(cpu)
133                 tracing_reset(tr, cpu);
134
135         start_branch_trace(tr);
136 }
137
138 static void branch_trace_reset(struct trace_array *tr)
139 {
140         stop_branch_trace(tr);
141 }
142
143 struct tracer branch_trace __read_mostly =
144 {
145         .name           = "branch",
146         .init           = branch_trace_init,
147         .reset          = branch_trace_reset,
148 #ifdef CONFIG_FTRACE_SELFTEST
149         .selftest       = trace_selftest_startup_branch,
150 #endif
151 };
152
153 __init static int init_branch_trace(void)
154 {
155         return register_tracer(&branch_trace);
156 }
157
158 device_initcall(init_branch_trace);
159 #else
160 static inline
161 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
162 {
163 }
164 #endif /* CONFIG_BRANCH_TRACER */
165
166 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
167 {
168         /*
169          * I would love to have a trace point here instead, but the
170          * trace point code is so inundated with unlikely and likely
171          * conditions that the recursive nightmare that exists is too
172          * much to try to get working. At least for now.
173          */
174         trace_likely_condition(f, val, expect);
175
176         /* FIXME: Make this atomic! */
177         if (val == expect)
178                 f->correct++;
179         else
180                 f->incorrect++;
181 }
182 EXPORT_SYMBOL(ftrace_likely_update);
183
184 struct ftrace_pointer {
185         void            *start;
186         void            *stop;
187 };
188
189 static void *
190 t_next(struct seq_file *m, void *v, loff_t *pos)
191 {
192         struct ftrace_pointer *f = m->private;
193         struct ftrace_branch_data *p = v;
194
195         (*pos)++;
196
197         if (v == (void *)1)
198                 return f->start;
199
200         ++p;
201
202         if ((void *)p >= (void *)f->stop)
203                 return NULL;
204
205         return p;
206 }
207
208 static void *t_start(struct seq_file *m, loff_t *pos)
209 {
210         void *t = (void *)1;
211         loff_t l = 0;
212
213         for (; t && l < *pos; t = t_next(m, t, &l))
214                 ;
215
216         return t;
217 }
218
219 static void t_stop(struct seq_file *m, void *p)
220 {
221 }
222
223 static int t_show(struct seq_file *m, void *v)
224 {
225         struct ftrace_branch_data *p = v;
226         const char *f;
227         unsigned long percent;
228
229         if (v == (void *)1) {
230                 seq_printf(m, " correct incorrect  %% "
231                               "       Function                "
232                               "  File              Line\n"
233                               " ------- ---------  - "
234                               "       --------                "
235                               "  ----              ----\n");
236                 return 0;
237         }
238
239         /* Only print the file, not the path */
240         f = p->file + strlen(p->file);
241         while (f >= p->file && *f != '/')
242                 f--;
243         f++;
244
245         if (p->correct) {
246                 percent = p->incorrect * 100;
247                 percent /= p->correct + p->incorrect;
248         } else
249                 percent = p->incorrect ? 100 : 0;
250
251         seq_printf(m, "%8lu %8lu %3lu ", p->correct, p->incorrect, percent);
252         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
253         return 0;
254 }
255
256 static struct seq_operations tracing_likely_seq_ops = {
257         .start          = t_start,
258         .next           = t_next,
259         .stop           = t_stop,
260         .show           = t_show,
261 };
262
263 static int tracing_likely_open(struct inode *inode, struct file *file)
264 {
265         int ret;
266
267         ret = seq_open(file, &tracing_likely_seq_ops);
268         if (!ret) {
269                 struct seq_file *m = file->private_data;
270                 m->private = (void *)inode->i_private;
271         }
272
273         return ret;
274 }
275
276 static struct file_operations tracing_likely_fops = {
277         .open           = tracing_likely_open,
278         .read           = seq_read,
279         .llseek         = seq_lseek,
280 };
281
282 extern unsigned long __start_likely_profile[];
283 extern unsigned long __stop_likely_profile[];
284 extern unsigned long __start_unlikely_profile[];
285 extern unsigned long __stop_unlikely_profile[];
286
287 static struct ftrace_pointer ftrace_likely_pos = {
288         .start                  = __start_likely_profile,
289         .stop                   = __stop_likely_profile,
290 };
291
292 static struct ftrace_pointer ftrace_unlikely_pos = {
293         .start                  = __start_unlikely_profile,
294         .stop                   = __stop_unlikely_profile,
295 };
296
297 static __init int ftrace_branch_init(void)
298 {
299         struct dentry *d_tracer;
300         struct dentry *entry;
301
302         d_tracer = tracing_init_dentry();
303
304         entry = debugfs_create_file("profile_likely", 0444, d_tracer,
305                                     &ftrace_likely_pos,
306                                     &tracing_likely_fops);
307         if (!entry)
308                 pr_warning("Could not create debugfs 'profile_likely' entry\n");
309
310         entry = debugfs_create_file("profile_unlikely", 0444, d_tracer,
311                                     &ftrace_unlikely_pos,
312                                     &tracing_likely_fops);
313         if (!entry)
314                 pr_warning("Could not create debugfs"
315                            " 'profile_unlikely' entry\n");
316
317         return 0;
318 }
319
320 device_initcall(ftrace_branch_init);