Red Hat Bugzilla – Bug 469181
plymouth:nolog required to see kernel panic on ppc serial console systems
Last modified: 2013-09-02 02:29:05 EDT
Description of problem:
Unable to see that my system panic'd on boot when booting F10 on an IBM ppc (ibm-505-lp1) with no VGA (only serial console).
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Install F10 to IBM Power5 virtual guest
System appears to stop during bootup ... no messages supplied. sysrq-h works, so the kernel appears to be alive (responding). It hasn't gone into sysinit startup yet.
* Booting with plymouth:nolog shows a kernel panic was being hidden.
* See boot up at http://fpaste.org/paste/8280
So thinking about this more, I'm not sure there's much we can do on the plymouth side.
I mean it's not like we'll get notified of the panic or get given an opportunity to show it.
I guess the kernel should undo TIOCCONS before spewing the panic message.
Moving to kernel, but this issue seems a little tricky. I think we may end up having to WONTFIX it.
Alan, any thoughts on the TIOCCONS undo?
panic() calls don't go via TIOCCONS redirection
So the question is what is hiding them and why. Does plymouth use the syslog functions to hide kernel printk messages ?
no, just TIOCCONS
If that's not sufficient that would explain why bug 462172 is an issue.
I do remember doing some tests some time ago where i converted all messages to uppercase to show messages were getting redirected, and I'm pretty sure kernel messages were uppercase, too, at the time. But, who knows, I may have botched the test.
jlaska, is there a separate (probably already fixed) bug for the panic issue?
So I just confirmed that kernel messages don't get redirected.
Using this module here:
sudo sh -c 'echo "long ugly, gnarly message here" > /sys/kernel/echo/alert'
while the splash screen was going and the message overwrote the splash.
So it could be jlaska was only getting the panic if plymouth:nolog was specified and boot up was just spinning before the panic happened if plymouth:nolog wasn't specified.
What you actually want I think is to see man 2 syslog.
Now that may break panic() and I need to check that out and fix it if so
(In reply to comment #6)
> jlaska, is there a separate (probably already fixed) bug for the panic issue?
halfline: the kernel bug that was hidden is now fixed. See bug#469079. Oddly enough, I believe that involved selinux and tty handling (says the non-kernel guy)?
okay, I've commited this based on man 2 syslog:
So one possible explanation for the behavior described in the last paragraph of comment 7 is the bug that this commit fixed:
jlaska do you know if you were booting with plymouth:debug when this problem happened?
Unfortunately, I can't recall and my fpaste.org seems to have been trashed. Apologies, I won't be relying fpaste.org for boot logs in bug reports.
well that's as plausible an explanation as any I guess. Let's go with it.
So, to summarize
1) kernel panic wasn't getting suppressed it just wasn't happening, because a different bug was making things spin.
2) adding nolog worked around the "spin bug" but ran into the panic issue
3) both of those bugs have been fixed
4) plymouth is now suppressing kernel messages, but wasn't before
5) Alan is going to check if this new found suppression is going to stop panics from showing up. If it turns out panics *do* show up okay then we can just close this report NOTABUG
This bug appears to have been reported against 'rawhide' during the Fedora 10 development cycle.
Changing version to '10'.
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