[lttng-dev] SIG33 message

[sboisvert@gydle.com (Sebastien Boisvert)]

On 2019-04-16 2:12 p.m., Mathieu Desnoyers wrote:
[snip]
> 
> Hi Sebastien,
> 
> This part of the ring buffer should only be used by the consumer daemon through
> liblttng-ust-ctl.so, never from the traced applications.
> 
> So I keep suspecting that it's NPTL's use of SIG33 which is causing an old
> version of gdb to trap, ref: https://gdb.sourceware.narkive.com/SzqG56iA/program-received-signal-sig33-real-time-event-33
> 
> Thanks,
> 
> Mathieu
> 

If it is the case that an old gdb is involved,
then it is unrelated to this kill() call site in the LTTng-UST source code:

    libringbuffer/ring_buffer_frontend.c:767:	kill(getpid(), LTTNG_UST_RB_SIG_TEARDOWN);

because LTTNG_UST_RB_SIG_TEARDOWN is SIGRTMIN + 2. According to the man page of signal(7) [1],
SIGRTMIN is 34 (Native Posix Thread Library) or 35 (LinuxThreads, whatever that is).


The equation

    33 = SIGRTMIN + 2

is not satisfied with either 34 or 35.


So, is upgrading gdg the solution ?


[1] http://man7.org/linux/man-pages/man7/signal.7.html


[snip]