Optimisation: only fix pending events once per lazy update

Suggested-by: Yang Wang <yangw.wang5@unb.ca>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Version 2.2.0-rc1

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: tracepoint instrumentation constructor order issue

If the linker decides to run a constructor from a tracepoint probe
before the constructor from the application, a recent modification
(commit 558b9d86247004f8e9bbaf8c982f3b2b182093d1) allowed that the wrong
constructor execution order could prohibit the program's tracepoints
from being registered.

Fix this by making two separate constructors.

Fixes #487

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Documentation: update 2.0 to 2.x

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add demo test back as an example

Update the lttng-ust man page to point to doc/examples/demo instead of
the now moved /tests/demo.

Minor typo fix.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Don't rely on explicit context for filtering

Now $ctx can be used without having the contexts explicitly enabled on
the channel.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Implement per-context filtering

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: filter string comparison should check for literal

The prior fix "Fix: filter string wildcard comparison" missed check for
string literal.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

update tests/demo readme file

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add man page for lttng-ust-cyg-profile

[ Edit by Mathieu Desnoyers: minor edits, add reference from
lttng-ust(3) to lttng-ust-cyg-profile(3). ]

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: filter string wildcard comparison

wildcards * should match 0 or more characters (not 1 or more).

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: Remove test runner script

Deprecated by the use of Perl prove and test lists.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: forwarding of call_site argument to field

I ran some tests with the new function entry/exit instrumentations.

The tracepoint provider for lttng_ust_cyg_profile:func_entry and
func_exit does not properly forward the call_site argument to the
call_site field. The patch below fixes the problem.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add demo README

Explain that demo program is moved to lttng-tools.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Tests: Use Perl prove as the testsuite runner

Inspired by the test strategy deployed in lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove tests depending on consumerd

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Convert hello.cxx test to a build test

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Clean-up of configure.ac and tests/Makefile.am

Removal of disabled tests. Fixes ./configure failing
in distribution package because by missing Makefiles
in tests/ust-basic-tracing and tests/ust-multi-test.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Fix snprintf test and output result to TAP format

Replace the tap library with the one used by babeltrace's test suite which
offers more functionality and outputs in a truly TAP-compliant format.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Replace same_line_marker test with same_line_tracepoint

This new test is up to date and re-enabled strictly as a build test.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove tests-libustinstr-malloc

Moved to lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove exit-fast test

Moved to lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove fork test

Moved to lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove daemon test

Moved to lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove demo test

Moved to lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated test-nevents test

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated simple_include test

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated register_test test

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Convert hello-static-lib test to a build test

The runtime verification is handled by the "ust/linking" regression test
in lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Convert hello test to a build test only

The runtime verification is handled by the "ust/linking" regression test
in lttng-tools.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated libustctl_function_tests test

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated test hello2

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated dlopen test

Using dlopen to load the tracepoint providers is now discouraged as
specified in the lttng-ust man page.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated test basic long

Replaced by the ust-demo test in lttng-tools

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

Remove outdated test basic

This test is replaced by the ust-demo test in lttng-tools

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

cyg_profile: implement fast and verbose .so

The "fast" .so (liblttng-ust-cyg-profile-fast.so) is for use-cases where
we expect a complete event stream to be recorded, so we can skip
duplicate information.

The verbose .so (liblttng-ust-cyg-profile.so) is for use-cases where
events discarded are expected, and the trace analyzer needs extra
information to be able to reconstruct the program flow.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Performance: add unlikely to tracepoint dynamic linking test

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: _LGPL_SOURCE rcu dereference fix

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Implement liblttng-ust-cyg-profile function entry/exit instrumentation

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Minor fix: libc wrapper internal run script

Take arguments in the script too.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: ustctl_recv_register_event pointer mixup

Was causing some event names to appear as "" in metadata.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: allow enabling same events for two channels

Fix the following use-case:

  593  lttng create
  594  lttng enable-channel test1 -u
  595  lttng enable-event -u -a
  596  lttng enable-event -u -a -c test1
  597  lttng start

run ./demo-trace

  598  lttng stop
  600  lttng view |wc -l

Previously, we were seeing only 8 events (number of events written in a
single stream), but now we see 16 events (each event is dispatched into
two streams).

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add channel ID field to attr

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Remove useless else clause

Reported-by: Keun-O Park <keun-o.park@windriver.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

tracepoint: move "probe" test outside of loop

This is a slow-path optimisation.

Reported-by: Sahara <keun-o.park@windriver.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix uninitialized has_loglevel variable

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix clang warnings

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup: work-around clang unused result warning

Not useful for CHAN_WARN_ON() macro.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup compile warning

ustctl.c: In function 'ustctl_init':
ustctl.c:1772:2: warning: implicit declaration of function
'lttng_ring_buffer_client_overwrite_rt_init'
[-Wimplicit-function-declaration]
ustctl.c:1774:2: warning: implicit declaration of function
'lttng_ring_buffer_client_discard_rt_init'
[-Wimplicit-function-declaration]
ustctl.c: In function 'ustctl_exit':
ustctl.c:1781:2: warning: implicit declaration of function
'lttng_ring_buffer_client_discard_rt_exit'
[-Wimplicit-function-declaration]
ustctl.c:1783:2: warning: implicit declaration of function
'lttng_ring_buffer_client_overwrite_rt_exit'
[-Wimplicit-function-declaration]

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup: remove unused variables

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

tracepoint: Don't add NULL probes

Reported-by: Sahara <keun-o.park@windriver.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Remove mention of locking issues associated with dlopen usage

This notice has been removed from the README as part of revision
b834dead.

Add a warning relating to dlclose() usage detailed in issue 447 in both
the man page and the README file.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Implement read timer (for RT)

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Only flush when there are readers active

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add mutex for channel wakeup fd update

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: fields should be initialized to NULL

Fixes uninitialized pointer free.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Implement ustctl_duplicate_ust_object_data

Allow sessiond to duplicate its object data. Useful for per-uid buffers.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add channel wakeup fd to monitor close

Add channel wakeup fd, so consumer can keep its handle on the stream
wakeup_fd (for periodic timer flush), and yet still discover that an
application has closed a channel or exited.

Requires to be updated in locked-step with lttng-tools
"Add channel wakeup fd to monitor close"

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: refcount issue in lttng-ust-abi.c

The following scenario could lead to a segmentation fault in
applications when the sessiond disappears or when the application try to
exit. This is caused by incorrect handling of reference counts.

This can happen in very particular race scenario, described as follows:

1) The sessiond asks for "release" of one or more objects (e.g. a
   session object), but _without_ asking for release of _all_ objects
   referencing the session.
2) The application exits, thus calling objd_table_destroy(). It walks on
   all objects, decrementing their reference count, freeing memory when
   their reference count reaches "1".

However, here is the issue: since "release" has already been performed
by sessiond on the session object, this extra reference count unref
performed by objd_table_destroy() can make the session object disappear
while it is still needed by either the channel object or the enabler
object. Therefore, we can experience a segmentation fault when we try to
unref and free the channel or enabler objects within
objd_table_destroy().

Fix this issue by adding the concept of an "owner reference". Only
objd_table_destroy(), lttng_ust_objd_table_owner_cleanup(), "release"
commands, and failure paths of object creation are allowed to decrement
the owner reference. We restrict objd_table_destroy() and
lttng_ust_objd_table_owner_cleanup() to _only_ decrement refcount of
objects _if_ their owner reference is still held.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: only consumerd should print errors

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Implement ring buffer periodic buffer switch timer

The tricky part was the teardown. It must not race against neither
pending signals nor in-flight signal handler execution, otherwise the
timer handler could access freed channel data. Use a dedicated thread to
handle those signals, with a synchronization point between each handler
execution.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: ensure all probe providers have their symbols

Following the removal of metadata generation from UST, the probes cannot
find the tracepoint_dlopen() symbol. Ensure those probes can be built by
declaring this symbol within each probe.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Reactivate error printing

Print errors at buffer teardown if LTTNG_UST_DEBUG=1 is set (env. var.)
when launching the consumerd. This is possible now that consumerd owns
the buffers.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Unregister tracepoint probes when not needed

Ensure tracepoint probes are only connected when we meet these
conditions:

at least one enabler enables event && session active && channel enabled

We introduce a "tstate" flag in addition to "active/enabled".

Active and enabled fields are used to atomically enable/disable session
and channel, whereas the tstate flag is a "transient state" enable
state. It is used to update all events following a state change
transition. The actual effect of the state transition is committed
atomically with store to active/enabled flag.

Upon enable, we do:

tstate = 1
update all events
enable = 1;

Upon disable, we do the opposite:

enable = 0;
tstate = 0;
update all events

The purpose of this scheme is to allow atomic enable/disable of events
while allowing per-event probe registration to be performed
non-atomically.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup: remove now unused metadata code from UST

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: notification timeout logic

-1: wait forever
0 to 10ms: wait for 10ms
+10ms: wait for the specified amount.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: don't print error in comm proto connect on ENOENT

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: return expected error return values for sessiond

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: set wait/wake fd to -1 before close

Else triggers double-close race.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: Only notify socket should have timeout/nonblock

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: ustctl: return -EPIPE to sessiond if connection is closed

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: Add timeout on notification socket

Use the constructor timeout value. If an error occurs, shutdown() is
called on the socket, so the following attempts to use this socket will
fail very quickly.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Remove now unused metadata printf code

Metadata is now generated by sessiond.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Move metadata creation into lttng-sessiond and lttng-consumed

Includes fixes in type serialization. Also stop sending metadata channel
events.

Need to be applied in locked-step with lttng-tools commit:

"Move metadata creation into lttng-sessiond and lttng-consumed"

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add write metadata API to ust-ctl.h

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Move UST registry into sessiond and implement notifiers

Needs to be use in locked-step with lttng-tools

"Move UST registry into sessiond and implement notifiers" commit.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: don't flush-final for offset 0 if reader is on sub-buffer

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Use tp rcu link test in provider

Ensure we never trigger a null pointer exception.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Remove direct dependency of probes on urcu-bp

The filter feature added a direct dependency of probes providers against
urcu-bp .so, while linking them against liblttng-ust should suffice. Fix
this by using the tracepoint.h wrapper for rcu_dereference().

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Use urcu tls-compat.h

We can use the URCU_TLS() compatibility layer from userspace RCU to
support some BSD flavors that do not support __thread.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Lazy provider registration

Register probe providers lazily, so process startup time is not impacted
by the number of events (especially for large number of events) as long
as no UST tracing session is active.

Refs #446

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Always use lttng_get_probe_list_head to get probe list

Prepare lazy probe registration.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix static build

Move init_usterr() to snprintf, along with its ust_loglevel state.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Move LTTng-UST buffer ownership from application to consumer

Before this change, applications were performing allocation and teardown
of their buffers. Applications therefore had ownership of the buffers.
The shm and wait fd were passed from applications, though sessiond, to
consumerd through unix sockets.

This change moves ownership of buffers from applications to consumer.
This will allow sharing buffers across many processes in a near future.
It will also facilitate implementation of periodical timers on the
consumer side, now that it has ownership of channels and buffers
(also called streams). This imply that file descriptors on shm and
wakeup end of the pipe are now passed from the consumerd to sessiond,
then to applications, through unix sockets. Then, applications "map"
channel and streams into their own memory space. Channel control
structure is actually a copy for each application, while streams are a
shared memory map (shm) between consumerd and all applications that
write into it, and have a wake up file descriptor on the application
side.

Dependency on libuuid is now removed from lttng-ust, and moved to
lttng-tools, since the UUID is needed at channel and buffer allocation.

This commit needs to be used along with commit named
"Move LTTng-UST buffer ownership from application to consumer" in
lttng-tools.

Reviewed-by: David Goulet <dgoulet@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix package: don't distribute generated headers

Fixes #421

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: don't cancel already exited threads

Ensure we don't issue pthread_cancel() on already exited threads.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Scalability fix: tracepoint.c hash table size increase

Speed up process startup for applications with large number of
tracepoints (e.g. 16k in J9 vm) by increasing the tracepoint.c hash
table size from 64 to 4096.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Scalability fix for many events: event hash table size

Increase number of buckets for event hash table (per session) from 64 to
4096. This improves process startup time for J9 vm (with 16k
tracepoints) very significantly.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Speed up probe registration for large amount of events

LTTng-UST probe registration is O(n^2). I actually left a comment that
describes this, also implying that we can improve this if it becomes an
issue.

I've had a report from Yang Wang, who works on instrumenting the J9 VM,
that O(n^2) does not agree well with 16000 probes and tracepoints.

It appears that lttng_probe_register() is being too paranoid for its own
good. There are now many things that are guaranteed by the way probe
providers are being built.

We actually need to keep a check that no provider with the same name has
been registered (O(n) on the number of registered providers, could be
improved with a hash table if it ever becomes necessary).

Use an assert to check that each event name starts with its own provider
name (it would be an internal error within the provider if it's not the
case). (O(n) on the number of events within a provider)

The rest is just useless, so remove this O(n^2) check.

While we are there, remove the now unused
lttng_event_get()/lttng_event_put() functions.

Reported-by: Yang Wang <yangw.wang5@unb.ca>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add missing demo-trace shell script to dist tarball

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Documentation: add uuid package name for Fedora in README

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: missing test for lttng_ust_comm_should_quit in lttng-ust-comm.c

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Add compilation support for Tile architectures

Also add missing space on the mips line for OCD purposes.

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Documentation: clarify debian package name for uuid in README

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: comment in ust-ctl.h

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix I/O-related error values in ustctl

These internal ustctl API members document >=0 as OK values. Make sure
reply recv errors are returned as errors.

Clarify ustctl_create_stream() error values.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: David Goulet <dgoulet@efficios.com>

Introduce hash table for lttng_create_event_if_missing()

lttng_create_event_if_missing() takes a lot of CPU time with stress-test
applications containing 1000 different TRACEPOINT_EVENT() and 1000
individual tracepoint() call-site.

With tracing disabled:

time ./AppWith1000_lines_TP 0

real    0m2.487s
user    0m2.424s
sys     0m0.000s

Introducing this hash table cuts the overhead very significantly when
tracing is enabled:

Before patch:

 72.16%  AppWith1000_lin  liblttng-ust.so.0.0.0             [.] lttng_create_event_if_missing
 25.64%  AppWith1000_lin  AppWith1000_lines_TP              [.] a(int)

time ./AppWith1000_lines_TP 0

real    0m7.946s
user    0m7.864s
sys     0m0.000s

After patch:

 89.13%  AppWith1000_lin  AppWith1000_lines_TP              [.] a(int)
  3.30%  AppWith1000_lin  liblttng-ust.so.0.0.0             [.] lttng_create_event_if_missing

time ./AppWith1000_lines_TP 0

real    0m2.762s
user    0m2.692s
sys     0m0.004s

Acked-by: David Goulet <dgoulet@efficios.com>
Acked-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: don't build C++ example if a C++ compiler isn't available

By default lttng-ust builds a hello.cxx C++ example that demonstrates
the usage of the userspace tracing library in a C++ program.
Unfortunately, when no C++ support is available, the build of lttng-ust
fails just because of this example code. So we make the compilation of
this code conditional on whether a working C++ compiler was found.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Remove LIBFORMAT output in configure.

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Document dependency on libuuid

Fixes #418

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>