Re: Possible heisenbug? (Was: Serial console on Ultra10 - no login-prompt)
If your console is on a sunsab serial port (I'm not sure about the
Ultra10), you are seeing the same issue I've worked-around a bit but
there is no proper fix as of yet. See:
http://marc.theaimsgroup.com/?l=linux-ultrasparc&m=111263847715665&w=2
E
On Apr 12, 2005 10:40 AM, Olle Görling <olle@gorling.net> wrote:
> Hi again all,
>
> A bit more digging gave some utterly strange behavior, which I think
> might be a heisenbug [1].
>
> When mgetty is spawned, and is waiting for a login-name, I attached a
> strace to it with the following command:
>
> strace -ff -o /tmp/strace-mgetty -p <pid of mgetty>
>
> At first it gave the same results as before, bash hung right after
> printing the motd. I stopped the strace, and suddenly the PS1 prompt
> was there. Magic. I decided to test this further and came up with the
> following results:
>
> 1) When executing a command that generates output (such as 'ls /'),
> output shows up fine, but no PS1 until I attach a strace to the pid of
> bash.
> 2) When executing a command that doesn't generate output (such as 'cat
> /dev/null'), output shows up fine (well, not really as there is none),
> and so does the PS1-prompt UNLESS I've already attached a strace to the
> pid. If a strace was attached, I have to cancel it in order to get the
> PS1-prompt again.
>
> This seems to me as a problem that changes it behavior depending on
> wether it's being probed or not. Am I right?
>
> If this is the case - how can I isolate the problem? Who should I
> report this to - right now I'm not sure where the bug is (bash? mgetty?
> kernel?). Any suggestions appreciated.
>
> // Olle Görling
> olle@gorling.net
>
> [1] http://www.catb.org/~esr/jargon/html/H/heisenbug.html
>
>
--
E
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