[lttng-dev] I'm still getting empty ust traces using tracef
mathieu.desnoyers at efficios.com
Thu May 11 14:15:01 EDT 2023
On 2023-05-11 14:13, Mathieu Desnoyers via lttng-dev wrote:
> On 2023-05-11 12:36, Brian Hutchinson via lttng-dev wrote:
>> ... more background. I've always used ltt in the kernel so I don't
>> have much experience with the user side of it and especially
>> multi-threaded, multi-core so I'm probably missing some fundamental
>> concepts that I need to understand.
> Which are the exact versions of LTTng-UST and LTTng-Tools you are using
> now ? (2.13.N or which git commit ?)
Also, can you try using lttng-ust stable-2.13 branch, which includes the following commit ?
Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Date: Tue Feb 21 14:29:49 2023 -0500
Fix: Reevaluate LTTNG_UST_TRACEPOINT_DEFINE each time tracepoint.h is included
Fix issues with missing symbols in use-cases where tracef.h is included
before defining LTTNG_UST_TRACEPOINT_DEFINE, e.g.:
It is caused by the fact that tracef.h includes tracepoint.h in a
context which has LTTNG_UST_TRACEPOINT_DEFINE undefined, and this is not
re-evaluated for the following includes.
Fix this by lifting the definition code in tracepoint.h outside of the
header include guards, and #undef the old LTTNG_UST__DEFINE_TRACEPOINT
before re-defining it to its new semantic. Use a new
_LTTNG_UST_TRACEPOINT_DEFINE_ONCE include guard within the
LTTNG_UST_TRACEPOINT_DEFINE defined case to ensure symbols are not
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
>> On Thu, May 11, 2023 at 11:53 AM Brian Hutchinson
>> <b.hutchman at gmail.com> wrote:
>>> I posted a while ago (thread - Using lttng 2.11 and UST doesn't appear
>>> to work - getting empty trace files) about this problem I'm having
>>> with getting empty trace logs.
>>> I've since upgraded to lttng v2.13 and while I can do a simple hello
>>> world program with tracef and get events in the log files, my more
>>> complicated large multi-threaded app I'm trying to debug is still
>>> getting empty log file traces.
>>> I can list the user space events in my app.
>>> Next I do:
>>> lttng enable-event --userspace 'lttng_ust_tracef:*'
>>> ... to enable the events, start lttng, start my app, .... and I get a
>>> trace directory structure that's empty.
>>> I feel like I've read every thread in the archives about people having
>>> the same problem.
>>> I did try using LD_PRELOAD with various libs thinking that was the
>>> problem but so far I'm still getting empty traces.
>>> So far I've tried:
>>> I guess one question I have is how do I determine which "helper libs"
>>> I need to preload?
>>> The application I'm working on is made up of a bunch of smaller static
>>> libs linked together into one big executable and that is linked with
>>> -llttng-ust and -ldl.
>>> I'm pretty stuck at the moment. Anyone have any wisdom on what I
>>> might be doing wrong or how I can tell why I'm not getting events in
>>> the logs?
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