John Baldwin wrote:
> Yes, calling free() without Giant is about as good as calling fdrop() without
> Giant Alfred. :)

Alfred would be right, for per processor memory pools.  8-).

> >> And on the way into the system it does:
> >> lock process
> >> crhold() (which includes mutex ops)
> >> unlock process
> >
> > This isn't needed, at least afaik.
> Not strictly for the comparison as Julian and Terry pointed out since the race
> can occur anyway (i.e., you don't need the lock to see if p_ucred changed),
> however, if you are actually doing a crhold(), you want to make sure p_ucred
> isn't stale, so you need the proc lock.

No.  If you _depend_ on the frequency of change being low,
you can do this with only atomic reference counts.  See the
pseudo code in my other posting, in direct response to you.

-- Terry

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