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List:       linux-ha-dev
Subject:    Re: [Linux-ha-dev] limits for HA fail-over in Linux? (
From:       Alan Robertson <alanr () unix ! sh>
Date:       2004-05-11 21:10:10
Message-ID: 40A14132.8020300 () unix ! sh
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Dmitry Golubev wrote:
>>No one has yet figured out a better way to work around this kind of a bug
>>in general, so when encountering a kernel bug which hangs up a resource
>>today people still do what they've been doing on UNIX systems since the
>>1970s.
>>
>>They reboot.
> 
> 
> Well, how reboot (not hardware reset, but reboot or init 6 command; kernel 
> panics are something that should not happen, and there are software and 
> hardware ways to reset the computer in that case, but I suspect that in any 
> other case 'reboot' command is what you are referring to) is different from 
> what we are trying to do? YES, I want to do a so called "reboot" for some 
> processes? What reboot is doing such that kill can not? Is there any magic? 
> If not, that maybe let's try the same methods but not on the whole machine at 
> once but on some selected group of processes (that can easily be identified).

Processes get hung because of bugs in the kernel or hardware malfunctions. 
  There no no other reasons why any process becomes unkillable.  So, hung 
processes are not process problems, they are kernel problems.

So, rebooting very much does something that a kill of a single process 
doesn't.  It restarts the kernel from scratch.

[You really don't know what a reboot does?]

For kernel issues, I refer you to my previous email.  If you want to 
understand basic kernel issues like processes, the kernel, device drivers, 
rebooting, etc., you might want to read a book on the subject, or take a 
class.  "Understanding the Linux Kernel" might be a good choice.

If you want to fix the kernel, or change the UNIX/Linux process model, 
please take that discussion to the linux-kernel mailing list.  General 
Linux kernel changes are off-topic for this mailing list.

-- 
     Alan Robertson <alanr@unix.sh>

"Openness is the foundation and preservative of friendship...  Let me claim 
from you at all times your undisguised opinions." - William Wilberforce

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