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 |
9af5d97a | 10 | #include <limits.h> |
b4051ad8 | 11 | #include <stddef.h> |
3b402b40 MD |
12 | #include <sys/types.h> |
13 | #include <unistd.h> | |
4318ae1b MD |
14 | #include <lttng/ust-events.h> |
15 | #include <lttng/ust-tracer.h> | |
0466ac28 | 16 | #include <lttng/ringbuffer-context.h> |
9d315d6d | 17 | #include "common/compat/tid.h" |
8c90a710 | 18 | #include <urcu/tls-compat.h> |
fc80554e MJ |
19 | |
20 | #include "context-internal.h" | |
7dd08bec | 21 | #include "lttng-tracer-core.h" |
aab17bfe | 22 | |
3b402b40 MD |
23 | /* |
24 | * We cache the result to ensure we don't trigger a system call for | |
25 | * each event. | |
26 | */ | |
16adecf1 | 27 | static DEFINE_URCU_TLS(pid_t, cached_vtid); |
3b402b40 | 28 | |
a93bfc45 MD |
29 | /* |
30 | * Upon fork or clone, the TID assigned to our thread is not the same as | |
31 | * we kept in cache. Luckily, we are the only thread surviving in the | |
32 | * child process, so we can simply clear our cached version. | |
33 | */ | |
34 | void lttng_context_vtid_reset(void) | |
35 | { | |
98357ffd | 36 | CMM_STORE_SHARED(URCU_TLS(cached_vtid), 0); |
a93bfc45 MD |
37 | } |
38 | ||
3b402b40 | 39 | static |
4e48b5d2 | 40 | size_t vtid_get_size(void *priv __attribute__((unused)), |
2208d8b5 | 41 | size_t offset) |
3b402b40 MD |
42 | { |
43 | size_t size = 0; | |
44 | ||
b5457df5 | 45 | size += lttng_ust_ring_buffer_align(offset, lttng_ust_rb_alignof(pid_t)); |
3b402b40 MD |
46 | size += sizeof(pid_t); |
47 | return size; | |
48 | } | |
49 | ||
98357ffd MD |
50 | static inline |
51 | pid_t wrapper_getvtid(void) | |
52 | { | |
53 | pid_t vtid; | |
54 | ||
55 | vtid = CMM_LOAD_SHARED(URCU_TLS(cached_vtid)); | |
56 | if (caa_unlikely(!vtid)) { | |
0f029713 | 57 | vtid = lttng_gettid(); |
98357ffd MD |
58 | CMM_STORE_SHARED(URCU_TLS(cached_vtid), vtid); |
59 | } | |
60 | return vtid; | |
61 | } | |
62 | ||
3b402b40 | 63 | static |
4e48b5d2 | 64 | void vtid_record(void *priv __attribute__((unused)), |
b5457df5 | 65 | struct lttng_ust_ring_buffer_ctx *ctx, |
e7bc0ef6 | 66 | struct lttng_ust_channel_buffer *chan) |
3b402b40 | 67 | { |
98357ffd MD |
68 | pid_t vtid = wrapper_getvtid(); |
69 | ||
8936b6c0 | 70 | chan->ops->event_write(ctx, &vtid, sizeof(vtid), lttng_ust_rb_alignof(vtid)); |
3b402b40 MD |
71 | } |
72 | ||
77aa5901 | 73 | static |
4e48b5d2 | 74 | void vtid_get_value(void *priv __attribute__((unused)), |
daacdbfc | 75 | struct lttng_ust_ctx_value *value) |
77aa5901 | 76 | { |
98357ffd | 77 | value->u.s64 = wrapper_getvtid(); |
77aa5901 MD |
78 | } |
79 | ||
4e48b5d2 MD |
80 | static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( |
81 | lttng_ust_static_event_field("vtid", | |
82 | lttng_ust_static_type_integer(sizeof(pid_t) * CHAR_BIT, | |
83 | lttng_ust_rb_alignof(pid_t) * CHAR_BIT, | |
84 | lttng_ust_is_signed_type(pid_t), | |
85 | BYTE_ORDER, 10), | |
86 | false, false), | |
87 | vtid_get_size, | |
88 | vtid_record, | |
89 | vtid_get_value, | |
90 | NULL, NULL); | |
91 | ||
daacdbfc | 92 | int lttng_add_vtid_to_ctx(struct lttng_ust_ctx **ctx) |
3b402b40 | 93 | { |
a084756d | 94 | int ret; |
3b402b40 | 95 | |
4e48b5d2 | 96 | if (lttng_find_context(*ctx, ctx_field->event_field->name)) { |
a084756d MD |
97 | ret = -EEXIST; |
98 | goto error_find_context; | |
3b402b40 | 99 | } |
4e48b5d2 MD |
100 | ret = lttng_ust_context_append(ctx, ctx_field); |
101 | if (ret) | |
102 | return ret; | |
3b402b40 | 103 | return 0; |
a084756d | 104 | |
a084756d | 105 | error_find_context: |
a084756d | 106 | return ret; |
3b402b40 | 107 | } |
4158a15a MD |
108 | |
109 | /* | |
110 | * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
111 | */ | |
112 | void lttng_fixup_vtid_tls(void) | |
113 | { | |
8c90a710 | 114 | asm volatile ("" : : "m" (URCU_TLS(cached_vtid))); |
4158a15a | 115 | } |