On 12/04/2015 08:02 AM, mark wrote:
No, *you* don't understand what we're saying: pre-systemd, if the o/p
saw that one stmt before the panic, they could look at what the system
was doing *sequentially*, and so have an idea what it was failing on.
With systemd's parallelism, we have no clue, other than what it's
done, and no idea what's happening that's failing.
It has never been true that a kernel panic was necessarily caused by the
immediately preceding step in a sequential init. I ran into one
instance (back in 4.x days, incidentally, where 'x' was 1 or 2) where a
panic was caused by the tg3 driver, but it wasn't tickled until a
variable number of packets passed the interface, and it didn't happen
very often. Typically, when it happened it happened during ssh startup
(almost every time it occurred, in fact). But the root cause was the
tg3 driver module, not sshd. So having the last line before the panic
being the ssh startup was actually a hindrance rather than a help in
that case; I would have been looking for an sshd problem that didn't
actually exist.
I don't think that's an isolated instance, either. You need the module
information from the panic more than information on what was started
immediately prior to the panic. This was fixed without me having to
file a bug report, incidentally, and so there is no BZ # to point you to
that I recall, and a quick search of bugzilla doesn't show one for that
particular issue that I had. I ended up seeing that it was a tg3
problem after setting up a serial console and grabbing the panic output
from that. By the time I got to that point, the next update rollup for
CentOS 4 was coming down, and that was the end of that problem.
I keep thinking I'll track down the panic I saw a few months ago with
CentOS 7 and gkrellm on my hardware, but by the time I get enough 'round
toits' to do the troubleshooting the kernel has been updated, and I have
to wait on the debuginfo.....lather, rinse, repeat. Eventually I'll get
my timing right and see what is (or maybe is not) happening.
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