It's not supported on Mac or Windows but should always work on Chrome OS.

oysteine@: assigning to you as a tracing owner, could PTAL or re-route?

We need this functionality back quite badly, to debug performance regressions.
Thanks!

> it does not work on Linux/Mac/ Windows either, but I'm not sure if it's supposed to
No

Did you reproduce on a CrOS device? Which device?

We need somebody from CrOS to look into this. Very likely the path of /sys/kernel/debug/tracing changed or is not accessible anymore.
Neither Oystein nor I do CrOS development. Can somebody from CrOS land look into this?

cc-ing a bunch of folks who might help

The last I checked was Squawks, and we tried some other Chromebooks as well as CfM.

I seem to be able to repro the issue on M65 on samus while we can't repro on M66 eve or kevin.
Trying samus with M66.

Same issue on samus with M66

Do these CrOS devices have selinux? One posibility is that selinux is misconfigured on them and chrome can't access debugfs. If you do
dmesg | grep denied 
do you see any avc: denial message?

I see a lot of avc: denied messages.
There is also one with path /sys/kernel/debug

> There is also one with path /sys/kernel/debug

can you please paste it. that might be the culprit.

If I disable enforcement as suggested by Primiano, with setenforce 0, the per CPU traces are back.

Output of dmesg | grep denied: https://paste.googleplex.com/6701584935288832

okay it's definitely a selinux problem. We need to find where selinux policies live for CrOS.
olka@ in the meantime, if you are root on the device, you can workaround this by just typing "setenforce 0" on a terminal

Thanks, we'll give it a try!

Would it be possible to fix it for M67?

The bug really limits our ability to asses performance issues on CfM devices.
(Rooted devices cannot join meetings in the production environment.)

Thanks!

+kerrnel: any idea who might be an appropriate owner for this? It seems like an issue with selinux policies.