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/kern/kern_thread.c b/sys/kern/kern_thread.c
index 93ff5a7..3338005 100644
--- a/sys/kern/kern_thread.c
+++ b/sys/kern/kern_thread.c
@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 #include <sys/sched.h>
 #include <sys/sleepqueue.h>
+#include <sys/selinfo.h>
 #include <sys/turnstile.h>
 #include <sys/ktr.h>
 #include <sys/umtx.h>
@@ -206,6 +207,7 @@ thread_fini(void *mem, int size)
 	turnstile_free(td->td_turnstile);
 	sleepq_free(td->td_sleepqueue);
 	umtx_thread_fini(td);
+	seltdfini(td);
 }
 
 /*