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>
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_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_ctx_field
*field
,
59 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
60 struct lttng_channel
*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_ctx_field
*field
,
70 struct lttng_ctx_value
*value
)
72 value
->u
.s64
= wrapper_getvpid();
75 int lttng_add_vpid_to_ctx(struct lttng_ctx
**ctx
)
77 struct lttng_ctx_field
*field
;
79 field
= lttng_append_context(ctx
);
82 if (lttng_find_context(*ctx
, "vpid")) {
83 lttng_remove_context_field(ctx
, field
);
86 field
->event_field
.name
= "vpid";
87 field
->event_field
.type
.atype
= atype_integer
;
88 field
->event_field
.type
.u
.integer
.size
= sizeof(pid_t
) * CHAR_BIT
;
89 field
->event_field
.type
.u
.integer
.alignment
= lttng_alignof(pid_t
) * CHAR_BIT
;
90 field
->event_field
.type
.u
.integer
.signedness
= lttng_is_signed_type(pid_t
);
91 field
->event_field
.type
.u
.integer
.reverse_byte_order
= 0;
92 field
->event_field
.type
.u
.integer
.base
= 10;
93 field
->event_field
.type
.u
.integer
.encoding
= lttng_encode_none
;
94 field
->get_size
= vpid_get_size
;
95 field
->record
= vpid_record
;
96 field
->get_value
= vpid_get_value
;
97 lttng_context_update(*ctx
);