Fix: pass private data to context callbacks
[lttng-ust.git] / liblttng-ust / lttng-context-vpid.c
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c1ef86f0 1/*
c0c0989a 2 * SPDX-License-Identifier: LGPL-2.1-only
c1ef86f0 3 *
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4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 *
c0c0989a 6 * LTTng UST vpid context.
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7 */
8
3fbec7dc 9#define _LGPL_SOURCE
9af5d97a 10#include <limits.h>
b4051ad8 11#include <stddef.h>
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12#include <sys/types.h>
13#include <unistd.h>
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14#include <lttng/ust-events.h>
15#include <lttng/ust-tracer.h>
0466ac28 16#include <lttng/ringbuffer-context.h>
c1ef86f0 17
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18#include "context-internal.h"
19
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20/*
21 * We cache the result to ensure we don't trigger a system call for
22 * each event.
23 */
24static pid_t cached_vpid;
25
26static inline
98357ffd 27pid_t wrapper_getvpid(void)
c1ef86f0 28{
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29 pid_t vpid;
30
31 vpid = CMM_LOAD_SHARED(cached_vpid);
32 if (caa_unlikely(!vpid)) {
33 vpid = getpid();
34 CMM_STORE_SHARED(cached_vpid, vpid);
35 }
36 return vpid;
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37}
38
39/*
40 * Upon fork or clone, the PID assigned to our thread is not the same as
41 * we kept in cache.
42 */
43void lttng_context_vpid_reset(void)
44{
98357ffd 45 CMM_STORE_SHARED(cached_vpid, 0);
c1ef86f0 46}
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47
48static
4e48b5d2 49size_t vpid_get_size(void *priv __attribute__((unused)),
2208d8b5 50 size_t offset)
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51{
52 size_t size = 0;
53
dc325c1d 54 size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(pid_t));
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55 size += sizeof(pid_t);
56 return size;
57}
58
59static
4e48b5d2 60void vpid_record(void *priv __attribute__((unused)),
4cfec15c 61 struct lttng_ust_lib_ring_buffer_ctx *ctx,
e7bc0ef6 62 struct lttng_ust_channel_buffer *chan)
c1ef86f0 63{
98357ffd 64 pid_t vpid = wrapper_getvpid();
c1ef86f0 65
8936b6c0 66 chan->ops->event_write(ctx, &vpid, sizeof(vpid), lttng_ust_rb_alignof(vpid));
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67}
68
77aa5901 69static
4e48b5d2 70void vpid_get_value(void *priv __attribute__((unused)),
daacdbfc 71 struct lttng_ust_ctx_value *value)
77aa5901 72{
98357ffd 73 value->u.s64 = wrapper_getvpid();
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74}
75
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76static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field(
77 lttng_ust_static_event_field("vpid",
78 lttng_ust_static_type_integer(sizeof(pid_t) * CHAR_BIT,
79 lttng_ust_rb_alignof(pid_t) * CHAR_BIT,
80 lttng_ust_is_signed_type(pid_t),
81 BYTE_ORDER, 10),
82 false, false),
83 vpid_get_size,
84 vpid_record,
85 vpid_get_value,
86 NULL, NULL);
87
daacdbfc 88int lttng_add_vpid_to_ctx(struct lttng_ust_ctx **ctx)
c1ef86f0 89{
a084756d 90 int ret;
c1ef86f0 91
4e48b5d2 92 if (lttng_find_context(*ctx, ctx_field->event_field->name)) {
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93 ret = -EEXIST;
94 goto error_find_context;
c1ef86f0 95 }
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96 ret = lttng_ust_context_append(ctx, ctx_field);
97 if (ret)
98 return ret;
c1ef86f0 99 return 0;
a084756d 100
a084756d 101error_find_context:
a084756d 102 return ret;
c1ef86f0 103}
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