Commit | Line | Data |
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3b402b40 | 1 | /* |
e92f3e28 | 2 | * lttng-context-vtid.c |
3b402b40 MD |
3 | * |
4 | * LTTng UST vtid context. | |
5 | * | |
e92f3e28 MD |
6 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
7 | * | |
8 | * This library is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License as published by the Free Software Foundation; only | |
11 | * version 2.1 of the License. | |
12 | * | |
13 | * This library is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | * Lesser General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU Lesser General Public | |
19 | * License along with this library; if not, write to the Free Software | |
20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
3b402b40 MD |
21 | */ |
22 | ||
23 | #include <sys/types.h> | |
24 | #include <unistd.h> | |
4318ae1b MD |
25 | #include <lttng/ust-events.h> |
26 | #include <lttng/ust-tracer.h> | |
27 | #include <lttng/ringbuffer-config.h> | |
4158a15a | 28 | #include "ltt-tracer-core.h" |
aab17bfe MD |
29 | |
30 | #ifdef __linux__ | |
31 | #include <syscall.h> | |
32 | #endif | |
33 | ||
34 | #if defined(_syscall0) | |
35 | _syscall0(pid_t, gettid) | |
36 | #elif defined(__NR_gettid) | |
37 | static inline pid_t gettid(void) | |
38 | { | |
39 | return syscall(__NR_gettid); | |
40 | } | |
41 | #else | |
42 | #warning "use pid as tid" | |
43 | static inline pid_t gettid(void) | |
44 | { | |
45 | return getpid(); | |
46 | } | |
47 | #endif | |
3b402b40 MD |
48 | |
49 | /* | |
50 | * We cache the result to ensure we don't trigger a system call for | |
51 | * each event. | |
52 | */ | |
53 | static __thread pid_t cached_vtid; | |
54 | ||
a93bfc45 MD |
55 | /* |
56 | * Upon fork or clone, the TID assigned to our thread is not the same as | |
57 | * we kept in cache. Luckily, we are the only thread surviving in the | |
58 | * child process, so we can simply clear our cached version. | |
59 | */ | |
60 | void lttng_context_vtid_reset(void) | |
61 | { | |
62 | cached_vtid = 0; | |
63 | } | |
64 | ||
3b402b40 MD |
65 | static |
66 | size_t vtid_get_size(size_t offset) | |
67 | { | |
68 | size_t size = 0; | |
69 | ||
70 | size += lib_ring_buffer_align(offset, lttng_alignof(pid_t)); | |
71 | size += sizeof(pid_t); | |
72 | return size; | |
73 | } | |
74 | ||
75 | static | |
76 | void vtid_record(struct lttng_ctx_field *field, | |
4cfec15c | 77 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
3b402b40 MD |
78 | struct ltt_channel *chan) |
79 | { | |
b5a3dfa5 | 80 | if (caa_unlikely(!cached_vtid)) |
3b402b40 MD |
81 | cached_vtid = gettid(); |
82 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(cached_vtid)); | |
83 | chan->ops->event_write(ctx, &cached_vtid, sizeof(cached_vtid)); | |
84 | } | |
85 | ||
86 | int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx) | |
87 | { | |
88 | struct lttng_ctx_field *field; | |
89 | ||
90 | field = lttng_append_context(ctx); | |
91 | if (!field) | |
92 | return -ENOMEM; | |
93 | if (lttng_find_context(*ctx, "vtid")) { | |
94 | lttng_remove_context_field(ctx, field); | |
95 | return -EEXIST; | |
96 | } | |
97 | field->event_field.name = "vtid"; | |
98 | field->event_field.type.atype = atype_integer; | |
99 | field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT; | |
100 | field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT; | |
101 | field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t); | |
102 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
103 | field->event_field.type.u.basic.integer.base = 10; | |
104 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
105 | field->get_size = vtid_get_size; | |
106 | field->record = vtid_record; | |
107 | return 0; | |
108 | } | |
4158a15a MD |
109 | |
110 | /* | |
111 | * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
112 | */ | |
113 | void lttng_fixup_vtid_tls(void) | |
114 | { | |
115 | asm volatile ("" : : "m" (cached_vtid)); | |
116 | } |