Commit | Line | Data |
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3b402b40 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
3b402b40 | 3 | * |
e92f3e28 MD |
4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
5 | * | |
c0c0989a | 6 | * LTTng UST vtid context. |
3b402b40 MD |
7 | */ |
8 | ||
3fbec7dc | 9 | #define _LGPL_SOURCE |
b4051ad8 | 10 | #include <stddef.h> |
3b402b40 MD |
11 | #include <sys/types.h> |
12 | #include <unistd.h> | |
4318ae1b MD |
13 | #include <lttng/ust-events.h> |
14 | #include <lttng/ust-tracer.h> | |
15 | #include <lttng/ringbuffer-config.h> | |
ae4b659d | 16 | #include <ust-tid.h> |
8c90a710 | 17 | #include <urcu/tls-compat.h> |
7dd08bec | 18 | #include "lttng-tracer-core.h" |
aab17bfe | 19 | |
3b402b40 MD |
20 | /* |
21 | * We cache the result to ensure we don't trigger a system call for | |
22 | * each event. | |
23 | */ | |
16adecf1 | 24 | static DEFINE_URCU_TLS(pid_t, cached_vtid); |
3b402b40 | 25 | |
a93bfc45 MD |
26 | /* |
27 | * Upon fork or clone, the TID assigned to our thread is not the same as | |
28 | * we kept in cache. Luckily, we are the only thread surviving in the | |
29 | * child process, so we can simply clear our cached version. | |
30 | */ | |
31 | void lttng_context_vtid_reset(void) | |
32 | { | |
98357ffd | 33 | CMM_STORE_SHARED(URCU_TLS(cached_vtid), 0); |
a93bfc45 MD |
34 | } |
35 | ||
3b402b40 | 36 | static |
53569322 | 37 | size_t vtid_get_size(struct lttng_ctx_field *field, size_t offset) |
3b402b40 MD |
38 | { |
39 | size_t size = 0; | |
40 | ||
41 | size += lib_ring_buffer_align(offset, lttng_alignof(pid_t)); | |
42 | size += sizeof(pid_t); | |
43 | return size; | |
44 | } | |
45 | ||
98357ffd MD |
46 | static inline |
47 | pid_t wrapper_getvtid(void) | |
48 | { | |
49 | pid_t vtid; | |
50 | ||
51 | vtid = CMM_LOAD_SHARED(URCU_TLS(cached_vtid)); | |
52 | if (caa_unlikely(!vtid)) { | |
0f029713 | 53 | vtid = lttng_gettid(); |
98357ffd MD |
54 | CMM_STORE_SHARED(URCU_TLS(cached_vtid), vtid); |
55 | } | |
56 | return vtid; | |
57 | } | |
58 | ||
3b402b40 MD |
59 | static |
60 | void vtid_record(struct lttng_ctx_field *field, | |
4cfec15c | 61 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
7dd08bec | 62 | struct lttng_channel *chan) |
3b402b40 | 63 | { |
98357ffd MD |
64 | pid_t vtid = wrapper_getvtid(); |
65 | ||
66 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(vtid)); | |
67 | chan->ops->event_write(ctx, &vtid, sizeof(vtid)); | |
3b402b40 MD |
68 | } |
69 | ||
77aa5901 MD |
70 | static |
71 | void vtid_get_value(struct lttng_ctx_field *field, | |
53569322 | 72 | struct lttng_ctx_value *value) |
77aa5901 | 73 | { |
98357ffd | 74 | value->u.s64 = wrapper_getvtid(); |
77aa5901 MD |
75 | } |
76 | ||
3b402b40 MD |
77 | int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx) |
78 | { | |
79 | struct lttng_ctx_field *field; | |
80 | ||
81 | field = lttng_append_context(ctx); | |
82 | if (!field) | |
83 | return -ENOMEM; | |
84 | if (lttng_find_context(*ctx, "vtid")) { | |
85 | lttng_remove_context_field(ctx, field); | |
86 | return -EEXIST; | |
87 | } | |
88 | field->event_field.name = "vtid"; | |
89 | field->event_field.type.atype = atype_integer; | |
218deb69 MD |
90 | field->event_field.type.u.integer.size = sizeof(pid_t) * CHAR_BIT; |
91 | field->event_field.type.u.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT; | |
92 | field->event_field.type.u.integer.signedness = lttng_is_signed_type(pid_t); | |
93 | field->event_field.type.u.integer.reverse_byte_order = 0; | |
94 | field->event_field.type.u.integer.base = 10; | |
95 | field->event_field.type.u.integer.encoding = lttng_encode_none; | |
3b402b40 MD |
96 | field->get_size = vtid_get_size; |
97 | field->record = vtid_record; | |
77aa5901 | 98 | field->get_value = vtid_get_value; |
b2cc986a | 99 | lttng_context_update(*ctx); |
3b402b40 MD |
100 | return 0; |
101 | } | |
4158a15a MD |
102 | |
103 | /* | |
104 | * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
105 | */ | |
106 | void lttng_fixup_vtid_tls(void) | |
107 | { | |
8c90a710 | 108 | asm volatile ("" : : "m" (URCU_TLS(cached_vtid))); |
4158a15a | 109 | } |