Evgeniy Polyakov a e'crit :
On Sat, Oct 28, 2006 at 12:28:12PM +0200, Eric Dumazet ([email protected]) wrote:
I really dont understand how you manage to queue multiple kevents in the
'overflow list'. You just queue one kevent at most. What am I missing ?
There is no overflow list - it is a pointer to the first kevent in the
ready queue, which was not put into ring buffer. It is an optimisation,
which allows to not search for that position each time new event should
be placed into the buffer, when it starts to have an empty slot.
This overflow list (you may call it differently, but still it IS a list), is
not complete. I feel you add it just to make me happy, but I am not (yet :) )
For example, you make no test at kevent_finish_user_complete() time.
Obviously, you can have a dangling pointer, and crash your box in certain
conditions.
static void kevent_finish_user_complete(struct kevent *k, int deq)
{
struct kevent_user *u = k->user;
unsigned long flags;
if (deq)
kevent_dequeue(k);
spin_lock_irqsave(&u->ready_lock, flags);
if (k->flags & KEVENT_READY) {
+ if (u->overflow_event == k) {
+ /* MUST do something to change u->overflow_kevent */
+ }
list_del(&k->ready_entry);
k->flags &= ~KEVENT_READY;
u->ready_num--;
}
spin_unlock_irqrestore(&u->ready_lock, flags);
kevent_user_put(u);
call_rcu(&k->rcu_head, kevent_free_rcu);
}
Eric
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