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Re: proposed sysctl(9) changes

On Fri, 21 Aug 2009, David Young wrote:

I have been trying to diagnose and fix an obscure bug either in
sysctl(9) or in the way that I use it.  While I was looking, I found out
that it is possible for a sysctlnode to change address if any of its
siblings are added or removed, because its parent stores its value, and
the value of its siblings, in an array that can be rearranged from time
to time.

I think that sysctl(9) will be easier to use, and it will save some
copying and bookkeeping internally, if parents store pointers to their
children instead of the values of their children.  Just in case I find
time to make that so, let me know if there are complicating factors or
downsides that I am overlooking.

There are some games that get played by "helper" functions to which you might need to pay close attention. For example, the "value" that is kept in the sysctl node might actually be simply some sort of cookie that the helper function uses to access the real value.

I used this in the dbcool(4) driver, but can't remember from where I cloned the code.

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