FYI: inpcb/pcbinfo mutex -> rwlock at some point in the mid-distant future

[Bruce M. Simpson]

Robert Watson wrote:
> One of those issues is that we need to demonstrate to ourselves that 
> exclusive access contention is managed as well with rwlocks as with 
> sleep mutexes, as these locks would continue to be fairly highly 
> contended in TCP.  The other issue is that rwlocks don't support full 
> priority propagation for reader access, although Jeff Roberson has 
> recently improved fairness to writers with many readers.

Don't forget that p4 bms_netdev contains a number of optimizations for 
the multicast paths -- there are lock acquisitions which are quite often 
unnecessary, or whose granularity is too high for the data structure(s) 
which need to be shared.

BMS