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[remux] xochitl is not started for new rm2fb version in toltec #127

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JanLuca opened this issue May 21, 2021 · 6 comments · May be fixed by #128
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[remux] xochitl is not started for new rm2fb version in toltec #127

JanLuca opened this issue May 21, 2021 · 6 comments · May be fixed by #128

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@JanLuca
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JanLuca commented May 21, 2021

proc.list_procs uses the program name defined in /proc/<id>/stat to build up its process list. This causes the problem that it does not account that programs changed their argv[0] to be listed by a different cmdline.

Particularity, this behavior causes the problem that remux is not compatible with the new rm2fb version released on toltec for the update 2.6+ since rm2fb-server now uses xochitl instead of remarkable-shutdown [1]. To avoid the problem that it is listed by the wrong name it changes the cmdline to rm2fb-server [1] so that /proc/<id>/cmdline contains correctly rm2fb-server but since the underlying exe is xochitl the second value of /proc/<id>/stat is (xochitl).

This way remux assumes that xochitl --system is already started which is not correct.

I would either suggest to include a check in the process list code if the cmdline and stat differs or depend on systemctl start/stop xochitl to handle the execution and state of xochitl.

[1] toltec-dev/toltec@12e6fb4
@raisjn
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raisjn commented May 21, 2021

thanks for investigating! I thought this was fixed

cc @matteodelabre

@JanLuca
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JanLuca commented May 21, 2021

I think toltec-dev/toltec@12e6fb4 already includes a patch but this just changes cmdline. The problem is that according to man 5 proc the second field is always the name of the executable.

But I just tested it: The problem can be fixed by creating a symlink to /usr/bin/xochitl and call this. Then the exec name is correct in stat as well

@raisjn
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raisjn commented May 21, 2021 •
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regarding using systemctl to manage xochitl: the default xochitl.service has a watchdog which will restart the process if it doesn't ping every X minutes. this interferes with backgrounding xochitl. since I want to leave the system service mostly unmodified, remux behaves the way it does. if systemctl supports pause, can switch to that

for the symlink: is Toltec or rm2fb a good place to put a PR?

for stat vs cmdline: can remux switch to cmdline and things would work?

@JanLuca
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JanLuca commented May 21, 2021

I just try to solve this using a symlink and if this works I open a PR on toltec

@JanLuca
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JanLuca commented May 21, 2021 •
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Ok, the name in /proc/<id>/stat is not the problem. The problem is in the function check_args. It returns true if somewhere in a path is the name of argument. For example it returns true for the cmdline inotifywait -m -q --format %f -e DELETE /home/root/.local/share/remarkable/xochitl where the name is just the name of the data dir. I think the check logic has to be adapted but I have no time now to think about a better solution maybe you can take a look into it.

PS: I still opened a PR for the symlink fix: toltec-dev/toltec#359

@JanLuca JanLuca mentioned this issue May 25, 2021
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matteodelabre added a commit to toltec-dev/toltec that referenced this issue Jun 4, 2021
@matteodelabre
Update rm2fb to v0.0.4
9367908 
This update includes a change in the server code to set the server
process name to 'rm2fb-server' (instead of the default 'xochitl'). See
also #359 and rmkit-dev/rmkit#127.

Test plan: Started the 'rm2fb' service, retrieved the server PID, and
made sure that both `/proc/PID/cmdline` and `/proc/PID/stat` contained
'rm2fb-server' instead of 'xochitl'.
@matteodelabre matteodelabre mentioned this issue Jun 4, 2021
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matteodelabre added a commit to toltec-dev/toltec that referenced this issue Jun 6, 2021
@matteodelabre
Update rm2fb to v0.0.4 (#363)
d813cc2 
This update includes a change in the server code to set the server
process name to 'rm2fb-server' (instead of the default 'xochitl'). See
also #359 and rmkit-dev/rmkit#127.
@matteodelabre
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I think this can be closed, since the issue has been fixed in toltec-dev/toltec#363.

@raisjn raisjn closed this as completed Dec 14, 2021
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Fix matching of Proc::check_args if cmdline contains non-exe path JanLuca/rmkit
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@matteodelabre @JanLuca @raisjn