Le lundi 24 janvier 2011 Ã 14:37 +0100, Patrick McHardy a Ãcrit :
> On 24.01.2011 14:25, Pablo Neira Ayuso wrote:
> > On 24/01/11 14:12, Eric Dumazet wrote:
> >> Le lundi 24 janvier 2011 Ã 14:06 +0100, Pablo Neira Ayuso a Ãcrit :
> >>
> >>> Yes, we can use nf_conntrack_get (which does atomic_inc) instead. New
> >>> patch attached.
> >>
> >> I feel now a bit uncomfortable, sorry ;)
> >>
> >> Are we sure the refcount cannot reach 0 while we hold
> >> nf_conntrack_lock ?
> >
> > the ct deletion from the hash list is protected by spin lock, so
> > whatever deletion would wait until we have left the dump section.
> >
> > with this patch, the code looks like it was in 2.6.24 before the rcu stuff.
>
> Yeah, we definitely have a reference while the conntrack is contained
> in the hash table, and removal requires taking nf_conntrack_lock,
> therefor using the conntrack entry while holding the lock is valid.
Yes, but to clarify my question, is the following possible ?
CPU 0 CPU1
dump()
spin_lock()
....
if (not enough room in skb)
decrement last refcount
increment_ref_count()
spin_unlock();
since refcount hit 0,
spin_lock(nf_conntrack)
remove ct from hashes
If yes we should use the atomic_inc_not_zero() form.
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