[haiku-development] Re: Help needed for input_server debug and tracker crash
- From: Michael Lotz <mmlr@xxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Mon, 20 Jul 2020 22:55:54 +0200
On 20.07.20 21:18, Adrien Destugues wrote:
With these changes applied:
- Tracker crashes on boot
Tracker crashes because get_key_map() returns NULL/NULL in
src/add-ons/input_server/filters/shortcut_catcher/KeyInfos.cpp:125 which
it uses via libshortcuts_shared. A NULL check should be added here. The
reason get_key_map() returns NULL is that "_control_input_server_" in
src/kits/interface/Input.cpp times out talking to the input_server.
- input_server does not seem to work
It does work eventually, but it blocks because it tries to talk to
itself while it is not yet set up. The calls to retrieve the current
settings in initialization of MouseSettings by the input_server via
MouseSettings::_RetrieveSettings() in
src/preferences/input/MouseSettings.cpp will eventually call
_control_input_server_, trying to send a message to itself. Once all of
these have timed out, things return to normal.
- Overall the system seems very slow (the debug window draws its border
and the content only appears a few seconds later, I shut down the
system from the power button on my machine and the shutdown process
was also quite slow)
This is due to everything trying to retrieve infos from the input_server
via _control_input_server_ and having to time out.
This makes the thing a bit difficult to debug, since no interaction with
the machine seems possible. Any suggestion on how to investigate such
problems? Is KDL the only way?
I debugged this inside QEMU. With "-serial stdio" you can see the serial
debug output on the console. From there the stack trace of the crash is
visible, which pretty quickly leads to the problematic call from Tracker.
To figure out what input_server is up to, KDL is indeed the simplest
IMHO. KDL is a pretty nice place overall and allows to easily find where
things currently are. In this particular case things are made a bit more
complicated since the usual key combination for entering KDL is not
available as the input_server has not yet brought up the keyboard (I'd
usually use the QEMU monitor with "sendkey alt-sysrq-d"). In this
instance I've provoked a KDL by triggering a machine check exception
(from the QMEU monitor with "mce 0 0 0xff00000000000000 0 0 0"), but
this only works due to a pending patch on my side to enable MCEs.
With serial debug output available, adding some debug_printfs inside the
input_server startup would probably have lead to the problem reasonably
quickly as well.
Regards,
Michael
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