Jim Henderson wrote:
> On Sat, 22 Nov 2008 09:46:38 -0800, Darren New wrote:
> 
>> Jim Henderson wrote:
>>> why would you not be able to update it consistently?
>> You write the .h file. While trying to write the .so file, you A) don't
>> have permissions to do so,
> 
> The updater requires root rights to run, so it has permissions to do that.

Not always. See network-mounted file systems, file systems mounted 
read-only, write-protect tabs, etc.

>> B) find that it's open by someone else as a shared text segment, 
> 
> I don't believe that would matter,

You're mistaken.

> again, it's the inode that's open, and 
> when the file is overwritten a new inode is created and the old one is 
> destroyed.

Only if you unlink the old file then creat() a new one.  If you actually 
open the current file for writing (and it's executing or sticky in swap, 
and it has a shared text segment), you get an error, even as root.

>> C) run out of disk space,
> 
> That would create other problems as well

Yes? So?  We know it's bad and you should avoid it, yes.

Note that nobody expects "I ran out of disk space" (or "I ran out of 
file handles or swap space") to result in their root directory getting 
truncated, for example. So it's not so bad that it should leave other 
parts of your system in an inconsistent state.

I also left out "Linux out-of-memory killer randomly decided to nuke my 
process because someone else grabbed a bunch of memory."

>> D) have your process killed,
>> E) have the power fail,
>> ....
> 
> Yeah, those could happen and could introduce problems - so you just 
> reinstall the packages and that makes things consistent.

And until you do, things are broken. Which is kind of my point.

It's also not an orthogonal solution. Everyone has to reinvent the wheel 
for themselves when trying to update multiple files consistently.

And if the package manager updates the database *before* it updates the 
files, you might never know it.

-- 
Darren New / San Diego, CA, USA (PST)

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