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Re: Update Conflicts and kernel bugs

Wade Hampton wrote:
> On my FC6 x86_64 laptop, yum crashed twice and I had to remove the
> __db* files and rebuild the RPM DB to get it to work.   This is a 4-5
> year old problem with RPM (first seen with RH7 or RH8 and the newer
> Berkley DB).

I asked:
> How long ago was that, and which kernel? It seems to have been due to an
> unfortunate interaction between the Berkeley DB and a kernel bug, which
> was fixed in 2.6.19.

Wade replied:
> It was on 2.6.18-1.2868.fc6 and was a few days ago (I had not updated
> it for a few weeks).

Um. I wrote the above from memory -- it might have been *during* 2.6.19
that the bug got fixed.

> How would a kernel bug cause a problem with an application like Berkeley DB?

As I understand it, there was a "race condition" where shared mmap'ed
pages that had been changed in memory (from what they were on disk)
might (occasionally) not be marked as needing to be written back to

I ought to emphasise -- I'm not a kernel hacker. I don't have the
knowledge to follow what the kernel was doing or why it lost data. It's
just that I know the kernel crew have found an obscure kernel corruption
bug, that it was strongly suspected that this caused problems with the
Berkeley database, and that I personally had experienced RPM database
corruption several times. Since fixed kernels came out, I haven't
encountered RPM database corruption, and the incidence of people
complaining about it on this list has gone *way* down.

So now, I'm trying to find examples of people who have experienced RPM
database corruption with a recent kernel. If I'm right, and it was a
kernel bug, then there won't be anyone (unless their hardware is wonky).


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