Re: is flock broken in 2.4 or 2.5 kernels or what does this mean?

From: David Ford (david+cert@blue-labs.org)
Date: Wed Jul 24 2002 - 11:08:04 EST


(Alan)
Actually I posted a "is sendmail on crack?" question last month when
8.12.5 was released and this was in the release notes. We got a bunch
of confirmations that Linux flock() was broken due to the accounting.

David

J.A. Magallon wrote:

>On 2002.07.23 Alan Cox wrote:
>
>
>>On Tue, 2002-07-23 at 15:41, John Covici wrote:
>>
>>
>>>In the latest release notes of sendmail I have read the following:
>>>
>>> NOTE: Linux appears to have broken flock() again. Unless
>>> the bug is fixed before sendmail 8.13 is shipped,
>>> 8.13 will change the default locking method to
>>> fcntl() for Linux kernel 2.4 and later. You may
>>> want to do this in 8.12 by compiling with
>>> -DHASFLOCK=0. Be sure to update other sendmail
>>> related programs to match locking techniques.
>>>
>>>Can anyone tell me what this is all about -- is there any basis in
>>>reality for what they are saying?
>>>
>>>
>>First I've heard of it, so it would be useful if someone has access to
>>the sendmail problem report/test in question that shows it and I'll go
>>find out.
>>
>>
>>
>
>Perhaps if you have your spool over nfs:
>
>man flock:
>
>NOTES
> flock(2) does not lock files over NFS. Use fcntl(2)
> instead: that does work over NFS, given a sufficiently
> recent version of Linux and a server which supports lock­
> ing.
>
> flock(2) and fcntl(2) locks have different semantics with
> respect to forked processes and dup(2).
>
>
>

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