[src/trunk]: src/sys/kern Add kern.direct_select sysctl. Default to 0 for now.

[rmind <rmind%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/8b9b982402d7
branches:  trunk
changeset: 768917:8b9b982402d7
user:      rmind <rmind%NetBSD.org@localhost>
date:      Mon Aug 29 00:39:16 2011 +0000

description:
Add kern.direct_select sysctl.  Default to 0 for now.

diffstat:

 sys/kern/sys_select.c |  52 +++++++++++++++++++++++++++++++++++---------------
 1 files changed, 36 insertions(+), 16 deletions(-)

diffs (112 lines):

diff -r 7d2ee614d730 -r 8b9b982402d7 sys/kern/sys_select.c
--- a/sys/kern/sys_select.c     Mon Aug 29 00:36:20 2011 +0000
+++ b/sys/kern/sys_select.c     Mon Aug 29 00:39:16 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_select.c,v 1.35 2011/08/09 06:36:51 hannken Exp $  */
+/*     $NetBSD: sys_select.c,v 1.36 2011/08/29 00:39:16 rmind Exp $    */
 
 /*-
  * Copyright (c) 2007, 2008, 2009, 2010 The NetBSD Foundation, Inc.
@@ -84,7 +84,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_select.c,v 1.35 2011/08/09 06:36:51 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_select.c,v 1.36 2011/08/29 00:39:16 rmind Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -103,6 +103,7 @@
 #include <sys/atomic.h>
 #include <sys/socketvar.h>
 #include <sys/sleepq.h>
+#include <sys/sysctl.h>
 
 /* Flags for lwp::l_selflag. */
 #define        SEL_RESET       0       /* awoken, interrupted, or not yet polling */
@@ -147,6 +148,7 @@
 };
 
 static selcluster_t    *selcluster[SELCLUSTERS] __read_mostly;
+static int             direct_select __read_mostly = 0;
 
 /*
  * Select system call.
@@ -378,9 +380,7 @@
        fd_mask *ibitp, *obitp;
        int msk, i, j, fd, n;
        file_t *fp;
-       kmutex_t *lock;
 
-       lock = curlwp->l_selcluster->sc_lock;
        ibitp = (fd_mask *)(bits + ni * 0);
        obitp = (fd_mask *)(bits + ni * 3);
        n = 0;
@@ -408,15 +408,15 @@
                                fd_putfile(fd);
                        }
                        if (obits != 0) {
-#ifndef NO_DIRECT_SELECT
-                               if (obits != *ibitp)
+                               if (direct_select) {
+                                       kmutex_t *lock;
+                                       lock = curlwp->l_selcluster->sc_lock;
                                        mutex_spin_enter(lock);
-                               *obitp |= obits;
-                               if (obits != *ibitp)
+                                       *obitp |= obits;
                                        mutex_spin_exit(lock);
-#else
-                               *obitp |= obits;
-#endif
+                               } else {
+                                       *obitp |= obits;
+                               }
                        }
                        ibitp++;
                        obitp++;
@@ -715,15 +715,15 @@
                         */
                        l = sip->sel_lwp;
                        oflag = l->l_selflag;
-#ifndef NO_DIRECT_SELECT
-                       if (!sel_setevents(l, sip, events)) {
+
+                       if (!direct_select) {
+                               l->l_selflag = SEL_RESET;
+                       } else if (!sel_setevents(l, sip, events)) {
                                /* No events to return. */
                                mutex_spin_exit(lock);
                                return;
                        }
-#else
-                       l->l_selflag = SEL_RESET;
-#endif
+
                        /*
                         * If thread is sleeping, wake it up.  If it's not
                         * yet asleep, it will notice the change in state
@@ -932,3 +932,23 @@
                error = 0;
        return (error);
 }
+
+/*
+ * System control nodes.
+ */
+SYSCTL_SETUP(sysctl_select_setup, "sysctl select setup")
+{
+       const struct sysctlnode *node = NULL;
+
+       sysctl_createv(clog, 0, NULL, &node,
+               CTLFLAG_PERMANENT,
+               CTLTYPE_NODE, "kern", NULL,
+               NULL, 0, NULL, 0,
+               CTL_KERN, CTL_EOL);
+       sysctl_createv(clog, 0, &node, NULL,
+               CTLFLAG_PERMANENT | CTLFLAG_READWRITE,
+               CTLTYPE_INT, "direct_select",
+               SYSCTL_DESCR("Enable/disable direct select (for testing)"),
+               NULL, 0, &direct_select, 0,
+               CTL_CREATE, CTL_EOL);
+}