8. What does disable-event command of lttng do? With the
example(hello) provided by lttng-ust, I enabled all events with '-a
-u' and then disabled them again. I launched the example with gdb and
dumped the tracepoint's structure and then found its state was active.
It's supposed to be inactive here, right?
Can you provide the detail of commands you launched, and the result of
gdb printout ? Please run "hello" with LTTNG_UST_DEBUG=1 env. var set.
BTW: I didn't see any trace generated here with view command.
That is after the disable, right ?
Yes
Also, did you do a lttng start at some point in your test ?
Yes. Following three examples(A/B/C) provide the testing info for question 8:
Example A: None event
lttng create hello
lttng list hello
Tracing session hello: [active]
Trace path: /root/lttng-traces/hello-20120621-071913
lttng start
gdb ./hello
(gdb) file .libs/hello
(gdb) set env LTTNG_UST_DEBUG=1
(gdb) show env
...
LTTNG_UST_DEBUG=1
(gdb) br main
Breakpoint 1 at 0x80489b9: file hello.c, line 84.
(gdb) r
Starting program: /root/project/lttng/lttng-ust-2.0.2/tests/hello/.libs/hello
[Thread debugging using libthread_db enabled]
liblttng_ust_tracepoint[3341/3341]: just registered a tracepoints section from
0xb7fddd64 and having 1 tracepoints (in tracepoint_register_lib() at
tracepoint.c:638)
liblttng_ust_tracepoint[3341/3341]: registered tracepoint: lttng_ust:metadata
(in tracepoint_register_lib() at tracepoint.c:643)
libust[3341/3341]: just registered probe lttng_ust containing 1 events (in
ltt_probe_register() at ltt-probes.c:109)
libust[3341/3341]: Registered event probe "lttng_ust:metadata" with signature "const
char *, str" (in ltt_probe_register() at ltt-probes.c:118)
libust[3341/3341]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_metadata_client_init() at
ltt-ring-buffer-metadata-client.h:334)
libust[3341/3341]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_client_overwrite_init() at ltt-ring-buffer-client.h:584)
libust[3341/3341]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_client_discard_init() at ltt-ring-buffer-client.h:584)
[New Thread 0xb7dddb70 (LWP 3344)]
[New Thread 0xb75dcb70 (LWP 3345)]
libust[3341/3344]: Info: sessiond not accepting connections to local apps
socket (in ust_listener_thread() at lttng-ust-comm.c:699)
libust[3341/3344]: Waiting for local apps sessiond (in wait_for_sessiond() at
lttng-ust-comm.c:621)
libust[3341/3344]: Linux kernels 2.6.33 to 3.0 (with the exception of stable
versions) do not support FUTEX_WAKE on read-only memory mappings correctly.
Please upgrade your kernel (fix is commit
9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel mainline). LTTng-UST
will use polling mode fallback. (in wait_for_sessiond() at lttng-ust-comm.c:634)
libust[3341/3344]: Error: futex: Bad address (in wait_for_sessiond() at
lttng-ust-comm.c:636)
libust[3341/3344]: Info: sessiond not accepting connections to local apps
socket (in ust_listener_thread() at lttng-ust-comm.c:699)
libust[3341/3345]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3341/3345]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3341/3345]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3341/3345]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3341/3341]: just registered probe ust_tests_hello containing 2 events
(in ltt_probe_register() at ltt-probes.c:109)
libust[3341/3341]: Registered event probe "ust_tests_hello:tptest" with signature
"int, anint, int, netint, long *, values, char *, text, size_t, textlen, double, doublearg,
float, floatarg" (in ltt_probe_register() at ltt-probes.c:118)
libust[3341/3341]: Registered event probe "ust_tests_hello:tptest_sighandler" with
signature "" (in ltt_probe_register() at ltt-probes.c:118)
liblttng_ust_tracepoint[3341/3341]: just registered a tracepoints section from
0x804b6c4 and having 2 tracepoints (in tracepoint_register_lib() at
tracepoint.c:638)
liblttng_ust_tracepoint[3341/3341]: registered tracepoint:
ust_tests_hello:tptest_sighandler (in tracepoint_register_lib() at
tracepoint.c:643)
liblttng_ust_tracepoint[3341/3341]: registered tracepoint:
ust_tests_hello:tptest (in tracepoint_register_lib() at tracepoint.c:643)
Breakpoint 1, main (argc=1, argv=0xbffff754) at hello.c:84
84 if (argc == 2)
Missing separate debuginfos, use: debuginfo-install
glibc-2.12-1.47.el6_2.12.i686 libuuid-2.17.2-12.4.el6.i686
(gdb) p __tracepoint_ust_tests_hello___tptest
$1 = {name = 0x804a380 "ust_tests_hello:tptest", state = 0, probes = 0x0,
tracepoint_provider_ref = 0x804b724,
signature = 0x8049240 "int, anint, int, netint, long *, values, char *, text, size_t,
textlen, double, doublearg, float, floatarg", padding = '\000' <repeats 15 times>}
Notice here the __tracepoint_ust_tests_hello___tptest.state and
__tracepoint_ust_tests_hello___tptest.probes both are 0, which means no
register and API tracepoint doesn't invoke probe.
Example B: enable event ust_tests_hello:tptest
lttng create hello
lttng enable-event ust_tests_hello:tptest -u
lttng list hello
Tracing session hello: [inactive]
Trace path: /root/lttng-traces/hello-20120621-073315
=== Domain: UST global ===
Channels:
-------------
- channel0: [enabled]
Attributes:
overwrite mode: 0
subbufers size: 4096
number of subbufers: 4
switch timer interval: 0
read timer interval: 200
output: mmap()
Events:
ust_tests_hello:tptest (type: tracepoint) [enabled]
lttng start
gdb ./hello
(gdb) file .libs/hello
(gdb) set env LTTNG_UST_DEBUG=1
(gdb) show env
...
LTTNG_UST_DEBUG=1
(gdb) br main
Breakpoint 1 at 0x80489b9: file hello.c, line 84.
(gdb) r
Starting program: /root/project/lttng/lttng-ust-2.0.2/tests/hello/.libs/hello
[Thread debugging using libthread_db enabled]
liblttng_ust_tracepoint[3365/3365]: just registered a tracepoints section from
0xb7fddd64 and having 1 tracepoints (in tracepoint_register_lib() at
tracepoint.c:638)
liblttng_ust_tracepoint[3365/3365]: registered tracepoint: lttng_ust:metadata
(in tracepoint_register_lib() at tracepoint.c:643)
libust[3365/3365]: just registered probe lttng_ust containing 1 events (in
ltt_probe_register() at ltt-probes.c:109)
libust[3365/3365]: Registered event probe "lttng_ust:metadata" with signature "const
char *, str" (in ltt_probe_register() at ltt-probes.c:118)
libust[3365/3365]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_metadata_client_init() at
ltt-ring-buffer-metadata-client.h:334)
libust[3365/3365]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_client_overwrite_init() at ltt-ring-buffer-client.h:584)
libust[3365/3365]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_client_discard_init() at ltt-ring-buffer-client.h:584)
[New Thread 0xb7dddb70 (LWP 3368)]
libust[3365/3368]: Info: sessiond not accepting connections to local apps
socket (in ust_listener_thread() at lttng-ust-comm.c:699)
[New Thread 0xb75dcb70 (LWP 3369)]
libust[3365/3368]: Waiting for local apps sessiond (in wait_for_sessiond() at
lttng-ust-comm.c:621)
libust[3365/3368]: Linux kernels 2.6.33 to 3.0 (with the exception of stable
versions) do not support FUTEX_WAKE on read-only memory mappings correctly.
Please upgrade your kernel (fix is commit
9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel mainline). LTTng-UST
will use polling mode fallback. (in wait_for_sessiond() at lttng-ust-comm.c:634)
libust[3365/3368]: Error: futex: Bad address (in wait_for_sessiond() at
lttng-ust-comm.c:636)
libust[3365/3368]: Info: sessiond not accepting connections to local apps
socket (in ust_listener_thread() at lttng-ust-comm.c:699)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
liblttng_ust_tracepoint[3365/3369]: Registering probe to tracepoint
lttng_ust:metadata (in __tracepoint_probe_register() at tracepoint.c:426)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3369]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3365/3369]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3365/3365]: just registered probe ust_tests_hello containing 2 events
(in ltt_probe_register() at ltt-probes.c:109)
libust[3365/3365]: Registered event probe "ust_tests_hello:tptest" with signature
"int, anint, int, netint, long *, values, char *, text, size_t, textlen, double, doublearg,
float, floatarg" (in ltt_probe_register() at ltt-probes.c:118)
liblttng_ust_tracepoint[3365/3365]: Registering probe to tracepoint
ust_tests_hello:tptest (in __tracepoint_probe_register() at tracepoint.c:426)
libust[3365/3365]: Registered event probe "ust_tests_hello:tptest_sighandler" with
signature "" (in ltt_probe_register() at ltt-probes.c:118)
liblttng_ust_tracepoint[3365/3365]: just registered a tracepoints section from
0x804b6c4 and having 2 tracepoints (in tracepoint_register_lib() at
tracepoint.c:638)
liblttng_ust_tracepoint[3365/3365]: registered tracepoint:
ust_tests_hello:tptest_sighandler (in tracepoint_register_lib() at
tracepoint.c:643)
liblttng_ust_tracepoint[3365/3365]: registered tracepoint:
ust_tests_hello:tptest (in tracepoint_register_lib() at tracepoint.c:643)
Breakpoint 1, main (argc=1, argv=0xbffff754) at hello.c:84
84 if (argc == 2)
Missing separate debuginfos, use: debuginfo-install
glibc-2.12-1.47.el6_2.12.i686 libuuid-2.17.2-12.4.el6.i686
(gdb) p __tracepoint_ust_tests_hello___tptest
$1 = {name = 0x804a380 "ust_tests_hello:tptest", state = 1, probes = 0x804c258,
tracepoint_provider_ref = 0x804b724,
signature = 0x8049240 "int, anint, int, netint, long *, values, char *, text, size_t,
textlen, double, doublearg, float, floatarg", padding = '\000' <repeats 15 times>}
We can see __tracepoint_ust_tests_hello___tptest.state and
__tracepoint_ust_tests_hello___tptest.probes have been set, which means API
tracepoint can invoke probe callback function and generate trace info.
Example C: enable event and then disable it
lttng create hello
Session hello created.
Traces will be written in /root/lttng-traces/hello-20120621-074221
lttng enable-event ust_tests_hello:tptest -u
UST event ust_tests_hello:tptest created in channel channel0
lttng disable-event ust_tests_hello:tptest -u
UST event ust_tests_hello:tptest disabled in channel channel0 for session hello
lttng list hello
Tracing session hello: [inactive]
Trace path: /root/lttng-traces/hello-20120621-074221
=== Domain: UST global ===
Channels:
-------------
- channel0: [enabled]
Attributes:
overwrite mode: 0
subbufers size: 4096
number of subbufers: 4
switch timer interval: 0
read timer interval: 200
output: mmap()
Events:
ust_tests_hello:tptest (type: tracepoint) [disabled]
lttng start
gdb ./hello
(gdb) file .libs/hello
(gdb) set env LTTNG_UST_DEBUG=1
(gdb) show env
...
LTTNG_UST_DEBUG=1
(gdb) br main
Breakpoint 1 at 0x80489b9: file hello.c, line 84.
(gdb) r
Starting program: /root/project/lttng/lttng-ust-2.0.2/tests/hello/.libs/hello
[Thread debugging using libthread_db enabled]
liblttng_ust_tracepoint[3384/3384]: just registered a tracepoints section from
0xb7fddd64 and having 1 tracepoints (in tracepoint_register_lib() at
tracepoint.c:638)
liblttng_ust_tracepoint[3384/3384]: registered tracepoint: lttng_ust:metadata
(in tracepoint_register_lib() at tracepoint.c:643)
libust[3384/3384]: just registered probe lttng_ust containing 1 events (in
ltt_probe_register() at ltt-probes.c:109)
libust[3384/3384]: Registered event probe "lttng_ust:metadata" with signature "const
char *, str" (in ltt_probe_register() at ltt-probes.c:118)
libust[3384/3384]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_metadata_client_init() at
ltt-ring-buffer-metadata-client.h:334)
libust[3384/3384]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_client_overwrite_init() at ltt-ring-buffer-client.h:584)
libust[3384/3384]: LTT : ltt ring buffer client init
(in ltt_ring_buffer_client_discard_init() at ltt-ring-buffer-client.h:584)
[New Thread 0xb7dddb70 (LWP 3387)]
[New Thread 0xb75dcb70 (LWP 3388)]
libust[3384/3387]: Info: sessiond not accepting connections to local apps
socket (in ust_listener_thread() at lttng-ust-comm.c:699)
libust[3384/3387]: Waiting for local apps sessiond (in wait_for_sessiond() at
lttng-ust-comm.c:621)
libust[3384/3387]: Linux kernels 2.6.33 to 3.0 (with the exception of stable
versions) do not support FUTEX_WAKE on read-only memory mappings correctly.
Please upgrade your kernel (fix is commit
9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel mainline). LTTng-UST
will use polling mode fallback. (in wait_for_sessiond() at lttng-ust-comm.c:634)
libust[3384/3387]: Error: futex: Bad address (in wait_for_sessiond() at
lttng-ust-comm.c:636)
libust[3384/3387]: Info: sessiond not accepting connections to local apps
socket (in ust_listener_thread() at lttng-ust-comm.c:699)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
liblttng_ust_tracepoint[3384/3388]: Registering probe to tracepoint
lttng_ust:metadata (in __tracepoint_probe_register() at tracepoint.c:426)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3388]: message received
(in ust_listener_thread() at lttng-ust-comm.c:766)
libust[3384/3388]: message successfully sent (in send_reply() at
lttng-ust-comm.c:202)
libust[3384/3384]: just registered probe ust_tests_hello containing 2 events
(in ltt_probe_register() at ltt-probes.c:109)
libust[3384/3384]: Registered event probe "ust_tests_hello:tptest" with signature
"int, anint, int, netint, long *, values, char *, text, size_t, textlen, double, doublearg,
float, floatarg" (in ltt_probe_register() at ltt-probes.c:118)
liblttng_ust_tracepoint[3384/3384]: Registering probe to tracepoint
ust_tests_hello:tptest (in __tracepoint_probe_register() at tracepoint.c:426)
libust[3384/3384]: Registered event probe "ust_tests_hello:tptest_sighandler" with
signature "" (in ltt_probe_register() at ltt-probes.c:118)
liblttng_ust_tracepoint[3384/3384]: just registered a tracepoints section from
0x804b6c4 and having 2 tracepoints (in tracepoint_register_lib() at
tracepoint.c:638)
liblttng_ust_tracepoint[3384/3384]: registered tracepoint:
ust_tests_hello:tptest_sighandler (in tracepoint_register_lib() at
tracepoint.c:643)
liblttng_ust_tracepoint[3384/3384]: registered tracepoint:
ust_tests_hello:tptest (in tracepoint_register_lib() at tracepoint.c:643)
Breakpoint 1, main (argc=1, argv=0xbffff754) at hello.c:84
84 if (argc == 2)
Missing separate debuginfos, use: debuginfo-install
glibc-2.12-1.47.el6_2.12.i686 libuuid-2.17.2-12.4.el6.i686
(gdb) p __tracepoint_ust_tests_hello___tptest
$1 = {name = 0x804a380 "ust_tests_hello:tptest", state = 1, probes = 0x804c258,
tracepoint_provider_ref = 0x804b724,
signature = 0x8049240 "int, anint, int, netint, long *, values, char *, text, size_t,
textlen, double, doublearg, float, floatarg", padding = '\000' <repeats 15 times>}
Here __tracepoint_ust_tests_hello___tptest.state and
__tracepoint_ust_tests_hello___tptest.probes have been set, which means probe
callback function wiil be called by API tracepoint. But the event has been
disabled, is this necessary to call into the probe again? If this behavior is
normal, what's suppoed to do with disable-event command?
Any misunderstanding please fix me. Thanks
