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3b402b40 MD |
1 | /* |
2 | * (C) Copyright 2009-2011 - | |
3 | * Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
4 | * | |
5 | * LTTng UST vtid context. | |
6 | * | |
7 | * Dual LGPL v2.1/GPL v2 license. | |
8 | */ | |
9 | ||
10 | #include <sys/types.h> | |
11 | #include <unistd.h> | |
4318ae1b MD |
12 | #include <lttng/ust-events.h> |
13 | #include <lttng/ust-tracer.h> | |
14 | #include <lttng/ringbuffer-config.h> | |
4158a15a | 15 | #include "ltt-tracer-core.h" |
aab17bfe MD |
16 | |
17 | #ifdef __linux__ | |
18 | #include <syscall.h> | |
19 | #endif | |
20 | ||
21 | #if defined(_syscall0) | |
22 | _syscall0(pid_t, gettid) | |
23 | #elif defined(__NR_gettid) | |
24 | static inline pid_t gettid(void) | |
25 | { | |
26 | return syscall(__NR_gettid); | |
27 | } | |
28 | #else | |
29 | #warning "use pid as tid" | |
30 | static inline pid_t gettid(void) | |
31 | { | |
32 | return getpid(); | |
33 | } | |
34 | #endif | |
3b402b40 MD |
35 | |
36 | /* | |
37 | * We cache the result to ensure we don't trigger a system call for | |
38 | * each event. | |
39 | */ | |
40 | static __thread pid_t cached_vtid; | |
41 | ||
a93bfc45 MD |
42 | /* |
43 | * Upon fork or clone, the TID assigned to our thread is not the same as | |
44 | * we kept in cache. Luckily, we are the only thread surviving in the | |
45 | * child process, so we can simply clear our cached version. | |
46 | */ | |
47 | void lttng_context_vtid_reset(void) | |
48 | { | |
49 | cached_vtid = 0; | |
50 | } | |
51 | ||
3b402b40 MD |
52 | static |
53 | size_t vtid_get_size(size_t offset) | |
54 | { | |
55 | size_t size = 0; | |
56 | ||
57 | size += lib_ring_buffer_align(offset, lttng_alignof(pid_t)); | |
58 | size += sizeof(pid_t); | |
59 | return size; | |
60 | } | |
61 | ||
62 | static | |
63 | void vtid_record(struct lttng_ctx_field *field, | |
4cfec15c | 64 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
3b402b40 MD |
65 | struct ltt_channel *chan) |
66 | { | |
b5a3dfa5 | 67 | if (caa_unlikely(!cached_vtid)) |
3b402b40 MD |
68 | cached_vtid = gettid(); |
69 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(cached_vtid)); | |
70 | chan->ops->event_write(ctx, &cached_vtid, sizeof(cached_vtid)); | |
71 | } | |
72 | ||
73 | int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx) | |
74 | { | |
75 | struct lttng_ctx_field *field; | |
76 | ||
77 | field = lttng_append_context(ctx); | |
78 | if (!field) | |
79 | return -ENOMEM; | |
80 | if (lttng_find_context(*ctx, "vtid")) { | |
81 | lttng_remove_context_field(ctx, field); | |
82 | return -EEXIST; | |
83 | } | |
84 | field->event_field.name = "vtid"; | |
85 | field->event_field.type.atype = atype_integer; | |
86 | field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT; | |
87 | field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT; | |
88 | field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t); | |
89 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
90 | field->event_field.type.u.basic.integer.base = 10; | |
91 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
92 | field->get_size = vtid_get_size; | |
93 | field->record = vtid_record; | |
94 | return 0; | |
95 | } | |
4158a15a MD |
96 | |
97 | /* | |
98 | * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
99 | */ | |
100 | void lttng_fixup_vtid_tls(void) | |
101 | { | |
102 | asm volatile ("" : : "m" (cached_vtid)); | |
103 | } |