[lttng-dev] Bug in LTTng-UST
simon.marchi at polymtl.ca
Fri Dec 12 23:21:23 EST 2014
Actually, I think the problem comes from UST not handling when a
program dlcloses a lib. There is a simpler way to show the problem.
Just have an app dlopen a .so that has a tracepoint and dlclose it.
When the app quits, UST will try to unregister the tracepoint and
read/write in the memory previously mapped to the library, causing a
I have made a small example. You just need to click on "Download gist"
in  to download a tarball, and a then simple make should be enough.
Start a UST session with -u -a and run ./app. Segfault should ensue.
On 12 December 2014 at 19:54, Matthew Khouzam
<matthew.khouzam at ericsson.com> wrote:
> Hi, it appears as though if a tracepoint is in a so, loading it,
> unloading it and reloading it makes it no longer visible.
> To confirm this you can try out this repo :
> (I know, it's not a serious program... but the bug is serious, I think)
> You can get the demo files here
> make the program (make from the git dir)
> copy the contents of the baseq2 in the demo into the release/baseq2
> start a ust session
> run the program.
> Ignore the baddr deadlocks :)
> The tracepoint is not visible, it is located in the game.so file.
> Chances are though that the problem is on my side, but the evidence
> (single registration ) seems to indicate that this is an actual problem.
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
More information about the lttng-dev