2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 * LTTng UST vpid context.
12 #include <sys/types.h>
14 #include <lttng/ust-events.h>
15 #include <lttng/ust-tracer.h>
16 #include <lttng/ringbuffer-context.h>
18 #include "context-internal.h"
21 * We cache the result to ensure we don't trigger a system call for
24 static pid_t cached_vpid
;
27 pid_t
wrapper_getvpid(void)
31 vpid
= CMM_LOAD_SHARED(cached_vpid
);
32 if (caa_unlikely(!vpid
)) {
34 CMM_STORE_SHARED(cached_vpid
, vpid
);
40 * Upon fork or clone, the PID assigned to our thread is not the same as
43 void lttng_context_vpid_reset(void)
45 CMM_STORE_SHARED(cached_vpid
, 0);
49 size_t vpid_get_size(struct lttng_ust_ctx_field
*field
, size_t offset
)
53 size
+= lttng_ust_lib_ring_buffer_align(offset
, lttng_alignof(pid_t
));
54 size
+= sizeof(pid_t
);
59 void vpid_record(struct lttng_ust_ctx_field
*field
,
60 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
61 struct lttng_ust_channel_buffer
*chan
)
63 pid_t vpid
= wrapper_getvpid();
65 lttng_ust_lib_ring_buffer_align_ctx(ctx
, lttng_alignof(vpid
));
66 chan
->ops
->event_write(ctx
, &vpid
, sizeof(vpid
));
70 void vpid_get_value(struct lttng_ust_ctx_field
*field
,
71 struct lttng_ust_ctx_value
*value
)
73 value
->u
.s64
= wrapper_getvpid();
76 int lttng_add_vpid_to_ctx(struct lttng_ust_ctx
**ctx
)
78 struct lttng_ust_ctx_field
*field
;
79 struct lttng_ust_type_common
*type
;
82 type
= lttng_ust_create_type_integer(sizeof(pid_t
) * CHAR_BIT
,
83 lttng_alignof(pid_t
) * CHAR_BIT
,
84 lttng_ust_is_signed_type(pid_t
),
88 field
= lttng_append_context(ctx
);
93 if (lttng_find_context(*ctx
, "vpid")) {
95 goto error_find_context
;
97 field
->event_field
->name
= strdup("vpid");
98 if (!field
->event_field
->name
) {
102 field
->event_field
->type
= type
;
103 field
->get_size
= vpid_get_size
;
104 field
->record
= vpid_record
;
105 field
->get_value
= vpid_get_value
;
106 lttng_context_update(*ctx
);
111 lttng_remove_context_field(ctx
, field
);
113 lttng_ust_destroy_type(type
);