On 12-Feb-02 Terry Lambert wrote:
> 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.

Yes, the broken code with the race condition that can corrupt random kernel
structures long enough to trigger a panic or break a condition test in a branch
or loop.  I saw that, yes.

> -- Terry


John Baldwin <[EMAIL PROTECTED]>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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