Re: Hot-patching

[John Richard Moser]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1



Valdis.Kletnieks@xxxxxx wrote:
> On Tue, 20 Sep 2005 18:07:17 EDT, John Richard Moser said:
> 
> 
>>These bugfixes don't typically change the exported binary interface of
>>the existing functions being corrected, and so it would be feasible to
>>halt all processors and execute an atomic codepath to switch the symbols
>>in the running kernel to point to the replacement functions from the old
>>ones.  If big functions are split up into smaller ones, as long as the
>>interface is the same for all existing functions, it shouldn't matter as
>>well.
> 
> 
> I believe telco switch software has been doing patch-on-the-fly for quite
> a long time.  It's a royal pain in the butt, especially if you have any
> dynamic 'struct foo_ops' lurking.
> 
> And you can't just plop the code in either - let's say the fix includes "add
> a state bit to the 'struct foo_ctl' to track XYZ".  Now you need to think about
> the fact that there's likely kmalloc'ed struct foo_ctl's already out there
> that don't know about this bit.  Hilarity ensues....

In which case you can't make a hot-patch, unless you like watching your
kernel take a crap.

- --
All content of all messages exchanged herein are left in the
Public Domain, unless otherwise explicitly stated.

    Creative brains are a valuable, limited resource. They shouldn't be
    wasted on re-inventing the wheel when there are so many fascinating
    new problems waiting out there.
                                                 -- Eric Steven Raymond
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (GNU/Linux)
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

iD8DBQFDMJJDhDd4aOud5P8RAijUAJ9BPXQoVCeD5EzTXedBGaIz87SjsgCdEN21
6/2BUWcZ4HT4FwSFkWt5OEM=
=WjP8
-----END PGP SIGNATURE-----
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/