2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 * Copyright (C) 2020 Michael Jeanson <mjeanson@efficios.com>
7 * LTTng UST time namespace context.
13 #include <sys/types.h>
16 #include <lttng/ust-events.h>
17 #include <lttng/ust-tracer.h>
18 #include <lttng/ust-ringbuffer-context.h>
19 #include "common/compat/tid.h"
20 #include <urcu/tls-compat.h>
21 #include "lttng-tracer-core.h"
22 #include "common/ns.h"
23 #include "context-internal.h"
27 * We cache the result to ensure we don't stat(2) the proc filesystem on
30 static DEFINE_URCU_TLS_INIT(ino_t
, cached_time_ns
, NS_INO_UNINITIALIZED
);
33 ino_t
get_time_ns(void)
38 time_ns
= CMM_LOAD_SHARED(URCU_TLS(cached_time_ns
));
41 * If the cache is populated, do nothing and return the
42 * cached inode number.
44 if (caa_likely(time_ns
!= NS_INO_UNINITIALIZED
))
48 * At this point we have to populate the cache, set the initial
49 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
50 * number from the proc filesystem, this is the value we will
53 time_ns
= NS_INO_UNAVAILABLE
;
56 * /proc/thread-self was introduced in kernel v3.17
58 if (stat("/proc/thread-self/ns/time", &sb
) == 0) {
61 char proc_ns_path
[LTTNG_PROC_NS_PATH_MAX
];
63 if (snprintf(proc_ns_path
, LTTNG_PROC_NS_PATH_MAX
,
64 "/proc/self/task/%d/ns/time",
65 lttng_gettid()) >= 0) {
67 if (stat(proc_ns_path
, &sb
) == 0) {
74 * And finally, store the inode number in the cache.
76 CMM_STORE_SHARED(URCU_TLS(cached_time_ns
), time_ns
);
82 * The time namespace can change for 2 reasons
83 * * setns(2) called with the fd of a different time ns
84 * * clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWTIME flag
86 void lttng_context_time_ns_reset(void)
88 CMM_STORE_SHARED(URCU_TLS(cached_time_ns
), NS_INO_UNINITIALIZED
);
92 size_t time_ns_get_size(void *priv
__attribute__((unused
)),
93 struct lttng_ust_probe_ctx
*probe_ctx
__attribute__((unused
)),
98 size
+= lttng_ust_ring_buffer_align(offset
, lttng_ust_rb_alignof(ino_t
));
99 size
+= sizeof(ino_t
);
104 void time_ns_record(void *priv
__attribute__((unused
)),
105 struct lttng_ust_probe_ctx
*probe_ctx
__attribute__((unused
)),
106 struct lttng_ust_ring_buffer_ctx
*ctx
,
107 struct lttng_ust_channel_buffer
*chan
)
111 time_ns
= get_time_ns();
112 chan
->ops
->event_write(ctx
, &time_ns
, sizeof(time_ns
), lttng_ust_rb_alignof(time_ns
));
116 void time_ns_get_value(void *priv
__attribute__((unused
)),
117 struct lttng_ust_probe_ctx
*probe_ctx
__attribute__((unused
)),
118 struct lttng_ust_ctx_value
*value
)
120 value
->u
.u64
= get_time_ns();
123 static const struct lttng_ust_ctx_field
*ctx_field
= lttng_ust_static_ctx_field(
124 lttng_ust_static_event_field("time_ns",
125 lttng_ust_static_type_integer(sizeof(ino_t
) * CHAR_BIT
,
126 lttng_ust_rb_alignof(ino_t
) * CHAR_BIT
,
127 lttng_ust_is_signed_type(ino_t
),
128 LTTNG_UST_BYTE_ORDER
, 10),
135 int lttng_add_time_ns_to_ctx(struct lttng_ust_ctx
**ctx
)
139 if (lttng_find_context(*ctx
, ctx_field
->event_field
->name
)) {
141 goto error_find_context
;
143 ret
= lttng_ust_context_append(ctx
, ctx_field
);
153 * Force a read (imply TLS allocation for dlopen) of TLS variables.
155 void lttng_ust_time_ns_init_thread(int flags
)
157 __asm__
__volatile__ ("" : : "m" (URCU_TLS(cached_time_ns
)));
158 if (flags
& LTTNG_UST_INIT_THREAD_CONTEXT_CACHE
)