Refactor select to reduce contention and hide internal implementation

details from consumers.

 - Track individual selecters on a per-descriptor basis such that there
   are no longer collisions and after sleeping for events only those
   descriptors which triggered events must be rescaned.
 - Protect the selinfo (per descriptor) structure with a mtx pool mutex.
   mtx pool mutexes were chosen to preserve api compatibility with
   existing code which does nothing but bzero() to setup selinfo
   structures.
 - Use a per-thread wait channel rather than a global wait channel.
 - Hide select implementation details in a seltd structure which is
   opaque to the rest of the kernel.
 - Provide a 'selsocket' interface for those kernel consumers who wish to
   select on a socket when they have no fd so they no longer have to
   be aware of select implementation details.

Tested by:	kris
Reviewed on:	arch

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/sys/socketvar.h b/sys/sys/socketvar.h
index 83ef09438a7e..bc8df7b9fb84 100644
--- a/sys/sys/socketvar.h
+++ b/sys/sys/socketvar.h
@@ -546,6 +546,8 @@ int	sosetopt(struct socket *so, struct sockopt *sopt);
 int	soshutdown(struct socket *so, int how);
 void	sotoxsocket(struct socket *so, struct xsocket *xso);
 void	sowakeup(struct socket *so, struct sockbuf *sb);
+int	selsocket(struct socket *so, int events, struct timeval *tv,
+	    struct thread *td);
 
 #ifdef SOCKBUF_DEBUG
 void	sblastrecordchk(struct sockbuf *, const char *, int);