FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_tslog.c
1 /*-
2 * Copyright (c) 2017 Colin Percival
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD: releng/12.0/sys/kern/kern_tslog.c 327423 2017-12-31 09:21:01Z cperciva $");
29
30 #include <sys/param.h>
31 #include <sys/sbuf.h>
32 #include <sys/sysctl.h>
33 #include <sys/systm.h>
34 #include <sys/tslog.h>
35
36 #include <machine/atomic.h>
37 #include <machine/cpu.h>
38
39 #ifndef TSLOGSIZE
40 #define TSLOGSIZE 262144
41 #endif
42
43 static volatile long nrecs = 0;
44 static struct timestamp {
45 void * td;
46 int type;
47 const char * f;
48 const char * s;
49 uint64_t tsc;
50 } timestamps[TSLOGSIZE];
51
52 void
53 tslog(void * td, int type, const char * f, const char * s)
54 {
55 uint64_t tsc = get_cyclecount();
56 long pos;
57
58 /* Grab a slot. */
59 pos = atomic_fetchadd_long(&nrecs, 1);
60
61 /* Store record. */
62 if (pos < nitems(timestamps)) {
63 timestamps[pos].td = td;
64 timestamps[pos].type = type;
65 timestamps[pos].f = f;
66 timestamps[pos].s = s;
67 timestamps[pos].tsc = tsc;
68 }
69 }
70
71 static int
72 sysctl_debug_tslog(SYSCTL_HANDLER_ARGS)
73 {
74 int error;
75 struct sbuf *sb;
76 size_t i, limit;
77
78 /*
79 * This code can race against the code in tslog() which stores
80 * records: Theoretically we could end up reading a record after
81 * its slots have been reserved but before it has been written.
82 * Since this code takes orders of magnitude longer to run than
83 * tslog() takes to write a record, it is highly unlikely that
84 * anyone will ever experience this race.
85 */
86 sb = sbuf_new_for_sysctl(NULL, NULL, 1024, req);
87 limit = MIN(nrecs, nitems(timestamps));
88 for (i = 0; i < limit; i++) {
89 sbuf_printf(sb, "%p", timestamps[i].td);
90 sbuf_printf(sb, " %llu",
91 (unsigned long long)timestamps[i].tsc);
92 switch (timestamps[i].type) {
93 case TS_ENTER:
94 sbuf_printf(sb, " ENTER");
95 break;
96 case TS_EXIT:
97 sbuf_printf(sb, " EXIT");
98 break;
99 case TS_THREAD:
100 sbuf_printf(sb, " THREAD");
101 break;
102 case TS_EVENT:
103 sbuf_printf(sb, " EVENT");
104 break;
105 }
106 sbuf_printf(sb, " %s", timestamps[i].f ? timestamps[i].f : "(null)");
107 if (timestamps[i].s)
108 sbuf_printf(sb, " %s\n", timestamps[i].s);
109 else
110 sbuf_printf(sb, "\n");
111 }
112 error = sbuf_finish(sb);
113 sbuf_delete(sb);
114 return (error);
115 }
116
117 SYSCTL_PROC(_debug, OID_AUTO, tslog, CTLTYPE_STRING|CTLFLAG_RD|CTLFLAG_MPSAFE,
118 0, 0, sysctl_debug_tslog, "", "Dump recorded event timestamps");
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