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-config.h>
18 * We cache the result to ensure we don't trigger a system call for
21 static pid_t cached_vpid
;
24 pid_t
wrapper_getvpid(void)
28 vpid
= CMM_LOAD_SHARED(cached_vpid
);
29 if (caa_unlikely(!vpid
)) {
31 CMM_STORE_SHARED(cached_vpid
, vpid
);
37 * Upon fork or clone, the PID assigned to our thread is not the same as
40 void lttng_context_vpid_reset(void)
42 CMM_STORE_SHARED(cached_vpid
, 0);
46 size_t vpid_get_size(struct lttng_ctx_field
*field
, size_t offset
)
50 size
+= lib_ring_buffer_align(offset
, lttng_alignof(pid_t
));
51 size
+= sizeof(pid_t
);
56 void vpid_record(struct lttng_ctx_field
*field
,
57 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
58 struct lttng_channel
*chan
)
60 pid_t vpid
= wrapper_getvpid();
62 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(vpid
));
63 chan
->ops
->event_write(ctx
, &vpid
, sizeof(vpid
));
67 void vpid_get_value(struct lttng_ctx_field
*field
,
68 struct lttng_ctx_value
*value
)
70 value
->u
.s64
= wrapper_getvpid();
73 int lttng_add_vpid_to_ctx(struct lttng_ctx
**ctx
)
75 struct lttng_ctx_field
*field
;
77 field
= lttng_append_context(ctx
);
80 if (lttng_find_context(*ctx
, "vpid")) {
81 lttng_remove_context_field(ctx
, field
);
84 field
->event_field
.name
= "vpid";
85 field
->event_field
.type
.atype
= atype_integer
;
86 field
->event_field
.type
.u
.integer
.size
= sizeof(pid_t
) * CHAR_BIT
;
87 field
->event_field
.type
.u
.integer
.alignment
= lttng_alignof(pid_t
) * CHAR_BIT
;
88 field
->event_field
.type
.u
.integer
.signedness
= lttng_is_signed_type(pid_t
);
89 field
->event_field
.type
.u
.integer
.reverse_byte_order
= 0;
90 field
->event_field
.type
.u
.integer
.base
= 10;
91 field
->event_field
.type
.u
.integer
.encoding
= lttng_encode_none
;
92 field
->get_size
= vpid_get_size
;
93 field
->record
= vpid_record
;
94 field
->get_value
= vpid_get_value
;
95 lttng_context_update(*ctx
);