[15:07] <mreithub> Hi, I've stumbled onto an issue with linux-image-4.15.0-193-generic on 18.04LTS: Some (a few percent) of our machines will hang on boot since the kernel update (downgrade to .192 fixes the issue) and I think I've tracked the issue down to changed framebuffer code in fbmem.c (which according to the changelog attempts to fix a CVE).
[15:08] <mreithub> I'm pretty sure (not familiar with the code but I'll hazard a guess) that a duplicate lock_fb_info() call is to blame (which causes an attempted lock of an already-locked mutex) (in line 1153 of fbmem.c)
[15:10] <mreithub> I can provide recorded dmesg logs and other info for two of the affected systems (they've since been downgraded to .192 to get them working again, but everything else is unchanged)
[18:34] <cascardo> mreithub, this is being tracked and we can reproduce it already. let me poke people around here
[18:35] <cascardo> mreithub, did you open a bug for that? if you haven't, no need to, as we planned on opening a bug
[19:11] <cascardo> mreithub, https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1990690
[19:25] <Arun[m]12> Hi cascardo  any idea on the progress of https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1981433 please?
[19:29] <cascardo> Arun[m]12, no idea, I am not involved in that bug, sorry
[19:30] <Arun[m]12> cascardo: ok, thanks for the response.
[19:30] <Arun[m]12> Any idea how I can get help on fixing that issue please cascardo ?
[19:34] <cascardo> Arun[m]12, have you tried the oem-5.17 kernel?
[19:35] <cascardo> I have just pinged people here, perhaps, this may put this bug on some people's tracks. Fingers crossed.
[19:36] <cascardo> Otherwise, getting this fixed/supported upstream by poking whoever is the upstream maintainer is a nice shot too.
 "Arun, have you tried the oem-5.1..." <- Yes, I just tried, no luck with it.
[19:52] <Arun[m]12> [   11.845962] cs35l41_hda: probe of spi0-CSC3551:00-cs35l41-hda.0 failed with error -22
[19:52] <Arun[m]12> [   11.846034] cs35l41_hda: probe of spi0-CSC3551:00-cs35l41-hda.1 failed with error -22
[20:47] <cascardo> are those lines on the bug already? if not, you could add them. they might be useful
[21:21] <Arun[m]12> Added, thanks!
[22:58] <mreithub> @cascardo, thx, was afk when you answered. I was planning to file a bug report but didn't have the time before leaving the house... I've just read the report you posted and yes, that's the exact issue imo. I'll leave this chat session up in case there's anything I can help with, but I'll be off to bed now.