Keep track of the number of times we trigger a reschedule before the

context switch actually happens.

diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 4262d75..99b9abc 100644 (file)
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kern_synch.c,v 1.19 2000/03/03 11:46:09 art Exp $     */
+/*     $OpenBSD: kern_synch.c,v 1.20 2000/03/03 16:49:25 art Exp $     */
 /*     $NetBSD: kern_synch.c,v 1.37 1996/04/22 01:38:37 christos Exp $ */
 
 /*-
@@ -64,6 +64,14 @@
 u_char curpriority;            /* usrpri of curproc */
 int    lbolt;                  /* once a second sleep address */
 
+/*
+ * We need to keep track on how many times we call roundrobin before we
+ * actually attempt a switch (that is when we call mi_switch()).
+ * This is done so that some slow kernel subsystems can yield instead of
+ * blocking the scheduling.
+ */
+int    roundrobin_attempts;
+
 void roundrobin __P((void *));
 void schedcpu __P((void *));
 void updatepri __P((struct proc *));
@@ -79,6 +87,7 @@ roundrobin(arg)
 {
 
        need_resched();
+       roundrobin_attempts++;
        timeout(roundrobin, NULL, hz / 10);
 }
 
@@ -630,6 +639,13 @@ mi_switch()
 #endif
        cpu_switch(p);
        microtime(&runtime);
+
+       /*
+        * We reset roundrobin_attempts at exit, because cpu_switch could
+        * have looped in the idle loop and the attempts would increase
+        * leading to unjust punishment of an innocent process.
+        */
+       roundrobin_attempts = 0;
 }
 
 /*

diff --git a/sys/sys/kernel.h b/sys/sys/kernel.h
index 6267f75..cfe2685 100644 (file)
--- a/sys/sys/kernel.h
+++ b/sys/sys/kernel.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kernel.h,v 1.5 1996/08/11 20:39:07 niklas Exp $       */
+/*     $OpenBSD: kernel.h,v 1.6 2000/03/03 16:49:24 art Exp $  */
 /*     $NetBSD: kernel.h,v 1.11 1995/03/03 01:24:16 cgd Exp $  */
 
 /*-
@@ -67,5 +67,5 @@ extern int profhz;            /* profiling clock's frequency */
 extern int lbolt;              /* once a second sleep address */
 extern int tickdelta;
 extern long timedelta;
-
+extern int roundrobin_attempts;        /* number switch attempts before switch */