On Wed, 2008-10-01 at 13:06 -0400, Peter Memishian wrote: > > > You've deadlocked. The problem is that ip_join_allmulti() has bumped the > > > refcount on the ill and is waiting to enter the IPSQ, while the current > > > thread inside the IPSQ is waiting for the ill refcounts to drop > > > (ipsq_waitfor is 2 AKA ILL_DOWN). This is exactly the sort of problem I > > > was worried about when I warned about using ipsq_enter() a few weeks > back. > > > You should use ipsq_try_enter(), which will enqueue the request if it > > > cannot immediately complete. > > > > This is a major bummer, as the caller of ip_join_allmulti() doesn't have > > a STREAMS queue to pass in so that ipsq_try_enter() can work. It's kind > > of silly that the ipsq itself doesn't simply have some utility STREAMS > > queue that it can use for this purpose... > > :-( Another approach would be to acquire a soft reference using > ill_waiter_inc(), drop the ill reference, and then do an ipsq_enter(). > Note that ipsq_enter() can fail in that case if you race with a teardown > (ILL_CONDEMNED will be set), in which case you'll want to give up.
That sounds much more feasible. I was also thinking that I might be able to use the ill's read queue, which is done when processing STREAMS messages on the read-side that require exclusive access (calls to qwriter_ip() for example). But the ill_waiter_inc() idea sounds much more simple... -Seb
