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From: Mathieu Desnoyers <>
Subject: [RELEASE] LTTng-UST 2.9.7 (EOL), 2.10.6 (Linux user-space tracer)
Date: Thu, 17 Oct 2019 16:01:07 -0400 (EDT)
Message-ID: <> (raw)


We are pleased to announce the 2.9.7 (EOL) and 2.10.6 stable releases
of the LTTng-UST 2.9 and 2.10 stable branches.

LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer,
is a low-overhead application tracer. The library "liblttng-ust" enables
tracing of applications and libraries.

* New in this release:

Important fixes to the lttng-ust fd tracker ( were done,
taking care of locking the fd tracker across fork() in the
wrapper, eliminating hangs observed in the child if the parent was executing
close() concurrently with fork(). Also, given that close() is an async-signal-safe
function, ensure that the synchronization strategy is robust against signals
by disabling signals and using a TLS nesting counter when taking the fd tracker
lock. [1, 2]

Another important fix to the lttng-ust fd tracker is disabling thread
cancellation around fd tracker lock, and locking the fd tracker across
fork() in the wrapper. Failure to do so causes
deadlocks in child applications if a pthread cancellation is performed
on a thread while it ran the liblttng-ust-fd close(3) wrapper. [3]

The locking strategy of the LTTng perf counter contexts was revisited to
eliminate a deadlock occurring once in a while when using the perf counters
context with lttng-ust. [4]

Now that the release of LTTng-UST 2.11.0 is imminent, version 2.9.7 marks
the end of life (EOL) of the 2.9 stable branch of LTTng-UST.



Project website:
Download link:


Mathieu Desnoyers
EfficiOS Inc.

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