mirror of
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d76a89c9d8
As I found myself writing these for a MR think it would better
to have to easily available to point people to.
Another small change is that since c706e1f8c8 we no longer
default subscribe to drm-backend for the flight recorder so update docs
as well. Combined with this new file should actually explain better how
to make use of it.
Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
51 lines
1.8 KiB
ReStructuredText
51 lines
1.8 KiB
ReStructuredText
.. _debugging flight recorder:
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Debugging with Flight Recorder
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==============================
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Weston can write debug scopes data to a circular ring buffer. This ring
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buffer can be accessed through a debug key, assuming you have a keyboard
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attached, or in case Weston dies, through a coredump. This document describes
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how to access that data in the later case.
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The ring buffer data can be accessed with a gdb python script that searches
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the coredump file for the that ring buffer address in order to retrieve
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data from it.
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Prior to setting this up make sure that flight recorder is configured
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accordingly. Make sure that Weston is started with the debug scopes that
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you're interested into. For instance if you'd like to get the :samp:`drm-backend` one
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Weston should show when starting up:
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::
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Flight recorder: enabled, scopes subscribed: drm-backend
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For that Weston needs to be started with :samp:`--debug -f drm-backend`.
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Also, make sure that the system is configured to generate a core dump. Refer
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to :samp:`man core(5)` for how to do that.
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Next you'll need the `gdb python
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script <https://gitlab.freedesktop.org/wayland/weston/-/blob/main/doc/scripts/gdb/flight_rec.py>`_,
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as that will be needed to search for the ring buffer within the coredump.
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Finally, to make this easier and push everything from the ring buffer to a
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file, we would need to create a batch gdb file script to invoke the commands
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for us.
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As an example name that file :file:`test.gdb` and add the following to entries
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to it, making sure to adjust the path for the python script.
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::
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source /path/to/flight_rec.py
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display_flight_rec
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Then run the following commands to dump the contents of the ring buffer
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straight to a file:
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::
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$ gdb --batch --command=/path/to/test.gdb -q /path/to/test/weston/binary --core /path/to/coredump &> dump.log.txt
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