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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> | |
49c0da7d | 15 | #include <lttng/ust-tid.h> |
daeb93bb | 16 | #include "ltt-tracer-core.h" |
3b402b40 MD |
17 | |
18 | /* | |
19 | * We cache the result to ensure we don't trigger a system call for | |
20 | * each event. | |
21 | */ | |
22 | static __thread pid_t cached_vtid; | |
23 | ||
a93bfc45 MD |
24 | /* |
25 | * Upon fork or clone, the TID assigned to our thread is not the same as | |
26 | * we kept in cache. Luckily, we are the only thread surviving in the | |
27 | * child process, so we can simply clear our cached version. | |
28 | */ | |
29 | void lttng_context_vtid_reset(void) | |
30 | { | |
31 | cached_vtid = 0; | |
32 | } | |
33 | ||
3b402b40 MD |
34 | static |
35 | size_t vtid_get_size(size_t offset) | |
36 | { | |
37 | size_t size = 0; | |
38 | ||
39 | size += lib_ring_buffer_align(offset, lttng_alignof(pid_t)); | |
40 | size += sizeof(pid_t); | |
41 | return size; | |
42 | } | |
43 | ||
44 | static | |
45 | void vtid_record(struct lttng_ctx_field *field, | |
4cfec15c | 46 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
3b402b40 MD |
47 | struct ltt_channel *chan) |
48 | { | |
b5a3dfa5 | 49 | if (caa_unlikely(!cached_vtid)) |
3b402b40 MD |
50 | cached_vtid = gettid(); |
51 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(cached_vtid)); | |
52 | chan->ops->event_write(ctx, &cached_vtid, sizeof(cached_vtid)); | |
53 | } | |
54 | ||
55 | int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx) | |
56 | { | |
57 | struct lttng_ctx_field *field; | |
58 | ||
59 | field = lttng_append_context(ctx); | |
60 | if (!field) | |
61 | return -ENOMEM; | |
62 | if (lttng_find_context(*ctx, "vtid")) { | |
63 | lttng_remove_context_field(ctx, field); | |
64 | return -EEXIST; | |
65 | } | |
66 | field->event_field.name = "vtid"; | |
67 | field->event_field.type.atype = atype_integer; | |
68 | field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT; | |
69 | field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT; | |
70 | field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t); | |
71 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
72 | field->event_field.type.u.basic.integer.base = 10; | |
73 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
74 | field->get_size = vtid_get_size; | |
75 | field->record = vtid_record; | |
76 | return 0; | |
77 | } | |
daeb93bb MD |
78 | |
79 | /* | |
80 | * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
81 | */ | |
82 | void lttng_fixup_vtid_tls(void) | |
83 | { | |
84 | asm volatile ("" : : "m" (cached_vtid)); | |
85 | } |