[lttng-dev] Help needed: No UST events recorded

Tue Aug 4 09:09:48 EDT 2020

Hi Moritz,

>From the lttng-sessiond log:

PERROR - 08:04:45.465478146 [575/575]: Failed to open wait shm at /lttng-ust-wait-8: Function not implemented (in get_wait_shm() at shm.c:98)
DEBUG1 - 08:04:45.465496345 [575/575]: Failing to get the wait shm fd (in get_wait_shm() at shm.c:143)
Error: Failed to notify applications or create the wait shared memory.
Execution continues but there might be problems for already
running applications that wishes to register.

On the app side we see that the app never register:

libust[694/694]: Error: Error opening shm /lttng-ust-wait-8-0 (in get_wait_shm() at lttng-ust-comm.c:1241)
libust[694/694]: Warning: Unable to get map shm for local apps. Disabling LTTng-UST per-user tracing. (in setup_local_apps() at lttng-ust-comm.c:523)

Does the /dev/shm mount point exist?
Does your kernel support shared memory/tmpfs?

Cheers

On Tue, Aug 04, 2020 at 08:15:08AM +0000, PFLANZER Moritz wrote:
> Hi Jonathan,
> 
> Apologies that I forgot to mention which version of LTTng I'm using. I didn't build from master but downloaded the latest release archives for LTTng 2.12 "(Ta) Meilleure". "lttng --version" reports a corresponding "lttng (LTTng Trace Control) 2.12.1 - (Ta) Meilleure"
> 
> Please find the console log here: https://pastebin.com/PVzqrPvr
> and the lttng-sessiond.log here: https://pastebin.com/g3aXAcQg
> 
> Thanks,
> Moritz
> 
> 
> 
> Moritz Pflanzer
> Software Development Engineer
> 
> [cid:image001.png at 01D3BF6E.185110B0]
> 
> Räffelstrasse 28
> 
> 8045 Zürich
> E: moritz.pflanzer at hexagon.com<mailto:moritz.pflanzer at hexagon.com><mailto:carolin.siebert at hexagon.com>
> W: http://www.hexagongeosystems.com
> 
> ________________________________
> From: Jonathan Rajotte-Julien <jonathan.rajotte-julien at efficios.com>
> Sent: 03 August 2020 17:31
> To: PFLANZER Moritz <moritz.pflanzer at hexagon.com>
> Cc: lttng-dev at lists.lttng.org <lttng-dev at lists.lttng.org>
> Subject: Re: [lttng-dev] Help needed: No UST events recorded
> 
> This email is not from Hexagon’s Office 365 instance. Please be careful while clicking links, opening attachments, or replying to this email.
> 
> 
> Hi Moritz
> 
> What is your version of lttng-tools?
> 
>   lttng --version
> 
> Please run the `hello` executable using the LTTNG_UST_DEBUG env variable, while
> tracing, and provide the output.
> 
>   pkill lttng-sessiond
>   lttng-sessiond -b -vvv --verbose-consumer 2> /tmp/lttng-sessiond.log
>   lttng create
>   lttng enable-event -u -a
>   lttng start
>   LTTNG_UST_DEBUG=y ./hello
>   lttng stop
>   lttng destroy
>   pkill lttng-sessiond
> 
> Please also provide the /tmp/lttng-sessiond.log file via pastebin.
> 
> I suspect that if you cross-compiled lttng-ust from the master branch that
> lttng-tools is not using the same version, resulting in the application not
> being able to register to the lttng-sessiond.
> 
> Cheers
> 
> On Mon, Aug 03, 2020 at 09:35:25AM +0000, PFLANZER Moritz via lttng-dev wrote:
> > Hi all!
> >
> > I'm struggling to get userspace tracing working on an aarch64 platform (busybox on top of Linux 5.4.24 kernel). I followed the guidelines in the docs and am currently using this example program for testing: https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Flttng%2Flttng-ust%2Ftree%2Fmaster%2Fdoc%2Fexamples%2Fhello-static-lib&data=02%7C01%7C%7Ce141a6eb68ea4d4c93c508d837c25b99%7C1b16ab3eb8f64fe39f3e2db7fe549f6a%7C0%7C0%7C637320655210160415&sdata=lPbFWob0G4U22ncUmqfz12Ha42xOymctYWCOJC34oC8%3D&reserved=0
> > I cross-compiled lttng-ust and that example, but when I run the following commands on the platform no traces are recorded. If I use the same example on my x86 machine everything works as expected. (And kernelspace tracing is working on that aarch64 system.)
> >
> > Any hints where I could start investigating the issue are welcome.
> >
> > Regards,
> > Moritz
> >
> > ~ # pwd
> > /root
> > ~ # lttng create
> > Spawning a session daemon
> > Session auto-20200720-174509 created.
> > Traces will be written in /root/lttng-traces/auto-20200720-174509
> > ~ # lttng enable-event -au
> > All UST events are enabled in channel channel0
> > ~ # lttng start
> > Tracing started for session auto-20200720-174509
> > ~ # ./hello
> > Hello, World!
> > Tracing...  done.
> > ~ # lttng destroy
> > Session auto-20200720-174509 destroyed
> > ~ # ll
> > total 40
> > -rwxr-xr-x    1 root     root         39280 Jul 20 17:44 hello*
> >
> >
> >
> > Moritz Pflanzer
> > Software Development Engineer
> >
> > [cid:image001.png at 01D3BF6E.185110B0]
> >
> > Räffelstrasse 28
> >
> > 8045 Zürich
> > E: moritz.pflanzer at hexagon.com<mailto:moritz.pflanzer at hexagon.com><mailto:carolin.siebert at hexagon.com>
> > W: http://www.hexagongeosystems.com/
> 
> 
> 
> > _______________________________________________
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> > lttng-dev at lists.lttng.org
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> 
> 
> --
> Jonathan Rajotte-Julien
> EfficiOS

-- 
Jonathan Rajotte-Julien
EfficiOS