2 * (C) Copyright 2009-2011 -
3 * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 * LTTng UST vtid context.
7 * Dual LGPL v2.1/GPL v2 license.
10 #include <sys/types.h>
12 #include <lttng/ust-events.h>
13 #include <lttng/ust-tracer.h>
14 #include <lttng/ringbuffer-config.h>
15 #include "ltt-tracer-core.h"
21 #if defined(_syscall0)
22 _syscall0(pid_t
, gettid
)
23 #elif defined(__NR_gettid)
24 static inline pid_t
gettid(void)
26 return syscall(__NR_gettid
);
29 #warning "use pid as tid"
30 static inline pid_t
gettid(void)
37 * We cache the result to ensure we don't trigger a system call for
40 static __thread pid_t cached_vtid
;
43 * Upon fork or clone, the TID assigned to our thread is not the same as
44 * we kept in cache. Luckily, we are the only thread surviving in the
45 * child process, so we can simply clear our cached version.
47 void lttng_context_vtid_reset(void)
53 size_t vtid_get_size(size_t offset
)
57 size
+= lib_ring_buffer_align(offset
, lttng_alignof(pid_t
));
58 size
+= sizeof(pid_t
);
63 void vtid_record(struct lttng_ctx_field
*field
,
64 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
65 struct ltt_channel
*chan
)
67 if (caa_unlikely(!cached_vtid
))
68 cached_vtid
= gettid();
69 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(cached_vtid
));
70 chan
->ops
->event_write(ctx
, &cached_vtid
, sizeof(cached_vtid
));
73 int lttng_add_vtid_to_ctx(struct lttng_ctx
**ctx
)
75 struct lttng_ctx_field
*field
;
77 field
= lttng_append_context(ctx
);
80 if (lttng_find_context(*ctx
, "vtid")) {
81 lttng_remove_context_field(ctx
, field
);
84 field
->event_field
.name
= "vtid";
85 field
->event_field
.type
.atype
= atype_integer
;
86 field
->event_field
.type
.u
.basic
.integer
.size
= sizeof(pid_t
) * CHAR_BIT
;
87 field
->event_field
.type
.u
.basic
.integer
.alignment
= lttng_alignof(pid_t
) * CHAR_BIT
;
88 field
->event_field
.type
.u
.basic
.integer
.signedness
= lttng_is_signed_type(pid_t
);
89 field
->event_field
.type
.u
.basic
.integer
.reverse_byte_order
= 0;
90 field
->event_field
.type
.u
.basic
.integer
.base
= 10;
91 field
->event_field
.type
.u
.basic
.integer
.encoding
= lttng_encode_none
;
92 field
->get_size
= vtid_get_size
;
93 field
->record
= vtid_record
;
98 * Force a read (imply TLS fixup for dlopen) of TLS variables.
100 void lttng_fixup_vtid_tls(void)
102 asm volatile ("" : : "m" (cached_vtid
));