The signal handlers were performing mutex operations in the signal handlers
which is bad idea that may lead to deadlocks.
1. Implement a separate signal thread to handle the signals.
2. Use the glib provided signal GSource to avoid performing operations in
the signal handler.
Fix#186
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/487>
When the user sets filters, we should not trace ref counts of object that
are not traced. This optimizes the tracer by potentially avoiding
generating useless backtraces.
This feature was previously available only through the SIGUSR2 signal,
which meant it wasn't available on platforms that don't have UNIX
signals, such as Windows and with applications that already use
SIGUSR1 for something else.
Now we have action-signals for doing the same. These action signals
can also be used for fetching the checkpoint information
programmatically instead of printing to the debug log.
This allows programs to inspect the leaked objects directly, log them,
and so on. Unlike the existing mechanism to use SIGUSR1, this also
works on platforms that do not support UNIX signals, such as Windows
and with applications that already use SIGUSR1 for something else.
This will be useful in combination with the next commit when we add
API to get a list of active tracers so that consumers of the API can
easily distinguish tracer objects.
The code implicitly uses this value when the stack trace is not FULL.
Mostly useful for documenting the behaviour when each flag is passed
and for translating to/from strings.
This is an API break but that API has not been released yet.
We are passing a flag rather than a simple boolean as we can imagine
to implement more features in the future for example to retrieve a
stack trace for all the threads, etc..
Retrieving source file and line numbers is pretty
expensive while getting a stack trace, this new argument
allows the user to decide to retrieve a backtrace
without those infos instead which is much faster.
For example running $ GST_LEAKS_TRACER_STACK_TRACE=1 GST_DEBUG=GST_TRACER:7 \
GST_TRACERS=leaks time gst-launch-1.0 videotestsrc num-buffers=1 ! fakesink:
* With simple stack traces:
0.04s user 0.02s system 99% cpu 0.060 total
* With full stack traces:
0.66s user 0.23s system 96% cpu 0.926 total
https://bugzilla.gnome.org/show_bug.cgi?id=775423
- we know number of filter items is not going to change,
but compiler doesn't
- only do GST_IS_TRACER check for GObjects, not mini objects
- use non-type check cast macros in performance critical paths
