[lttng-dev] LTTng user-space callstacks

[Mathieu Desnoyers]

----- On Mar 26, 2020, at 1:39 PM, lttng-dev <lttng-dev at lists.lttng.org> wrote: 

> Hello!

> Currently, callstack collection in LTTng is only available for kernel-space
> events with context fields callstack-kernel and callstack-user .

> Is it expected that callstack collection for LTTng-UST will be added too? And if
> it is expected, then how soon?

Hi Valentin, 

It is something that would be interesting and useful, but a lot of work would 
be needed to have stack-walking this is fast enough and reentrant wrt signal 
handlers. Unfortunately, the backtrace(3) functions do not meet those 
requirements. 

Also, for gathering user-space callstacks from the kernel tracer, it only works if 
all user-space is compiled with frame pointers. This is also a limitation that would 
require a lot of work to overcome neatly. 

None of those features are currently on any roadmap due to lack of customers 
showing interest in getting this done. 

Thanks, 

Mathieu 

-- 
Mathieu Desnoyers 
EfficiOS Inc. 
http://www.efficios.com 
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