2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 * LTTng UST vpid context.
11 #include <sys/types.h>
13 #include <lttng/ust-events.h>
14 #include <lttng/ust-tracer.h>
15 #include <lttng/ringbuffer-context.h>
17 #include "context-internal.h"
20 * We cache the result to ensure we don't trigger a system call for
23 static pid_t cached_vpid
;
26 pid_t
wrapper_getvpid(void)
30 vpid
= CMM_LOAD_SHARED(cached_vpid
);
31 if (caa_unlikely(!vpid
)) {
33 CMM_STORE_SHARED(cached_vpid
, vpid
);
39 * Upon fork or clone, the PID assigned to our thread is not the same as
42 void lttng_context_vpid_reset(void)
44 CMM_STORE_SHARED(cached_vpid
, 0);
48 size_t vpid_get_size(struct lttng_ust_ctx_field
*field
, size_t offset
)
52 size
+= lib_ring_buffer_align(offset
, lttng_alignof(pid_t
));
53 size
+= sizeof(pid_t
);
58 void vpid_record(struct lttng_ust_ctx_field
*field
,
59 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
60 struct lttng_ust_channel_buffer
*chan
)
62 pid_t vpid
= wrapper_getvpid();
64 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(vpid
));
65 chan
->ops
->event_write(ctx
, &vpid
, sizeof(vpid
));
69 void vpid_get_value(struct lttng_ust_ctx_field
*field
,
70 struct lttng_ust_ctx_value
*value
)
72 value
->u
.s64
= wrapper_getvpid();
75 int lttng_add_vpid_to_ctx(struct lttng_ust_ctx
**ctx
)
77 struct lttng_ust_ctx_field
*field
;
78 struct lttng_ust_type_common
*type
;
81 type
= lttng_ust_create_type_integer(sizeof(pid_t
) * CHAR_BIT
,
82 lttng_alignof(pid_t
) * CHAR_BIT
,
83 lttng_is_signed_type(pid_t
),
87 field
= lttng_append_context(ctx
);
92 if (lttng_find_context(*ctx
, "vpid")) {
94 goto error_find_context
;
96 field
->event_field
->name
= strdup("vpid");
97 if (!field
->event_field
->name
) {
101 field
->event_field
->type
= type
;
102 field
->get_size
= vpid_get_size
;
103 field
->record
= vpid_record
;
104 field
->get_value
= vpid_get_value
;
105 lttng_context_update(*ctx
);
110 lttng_remove_context_field(ctx
, field
);
112 lttng_ust_destroy_type(type
);