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, 8 insertions, 8 deletions

diff --git a/sys/sys/selinfo.h b/sys/sys/selinfo.h
index 946da8c..2d2f848 100644
--- a/sys/sys/selinfo.h
+++ b/sys/sys/selinfo.h
@@ -35,26 +35,26 @@
 
 #include <sys/event.h>		/* for struct klist */
 
+struct selfd;
+TAILQ_HEAD(selfdlist, selfd);
+
 /*
  * Used to maintain information about processes that wish to be
  * notified when I/O becomes possible.
  */
 struct selinfo {
-	TAILQ_ENTRY(selinfo)	si_thrlist;	/* list hung off of thread */
-	struct	thread *si_thread;	/* thread waiting */
-	struct	knlist si_note;	/* kernel note list */
-	short	si_flags;	/* see below */
+	struct selfdlist	si_tdlist;	/* List of sleeping threads. */
+	struct knlist		si_note;	/* kernel note list */
+	struct mtx		*si_mtx;	/* Lock for tdlist. */
 };
-#define	SI_COLL	0x0001		/* collision occurred */
 
-#define	SEL_WAITING(si)	\
-	((si)->si_thread != NULL || ((si)->si_flags & SI_COLL) != 0)
+#define	SEL_WAITING(si)		(!TAILQ_EMPTY(&(si)->si_tdlist))
 
 #ifdef _KERNEL
-void	clear_selinfo_list(struct thread *td);
 void	selrecord(struct thread *selector, struct selinfo *sip);
 void	selwakeup(struct selinfo *sip);
 void	selwakeuppri(struct selinfo *sip, int pri);
+void	seltdfini(struct thread *td);
 #endif
 
 #endif /* !_SYS_SELINFO_H_ */