[src/trunk]: src/sys/kern Comments

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

details:   https://anonhg.NetBSD.org/src/rev/6a1bf7ec6055
branches:  trunk
changeset: 850166:6a1bf7ec6055
user:      ad <ad%NetBSD.org@localhost>
date:      Fri Mar 27 00:13:52 2020 +0000

description:
Comments

diffstat:

 sys/kern/kern_softint.c |  17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

diffs (50 lines):

diff -r 9ac88cae95ce -r 6a1bf7ec6055 sys/kern/kern_softint.c
--- a/sys/kern/kern_softint.c   Thu Mar 26 22:43:19 2020 +0000
+++ b/sys/kern/kern_softint.c   Fri Mar 27 00:13:52 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_softint.c,v 1.63 2020/03/26 20:19:06 ad Exp $     */
+/*     $NetBSD: kern_softint.c,v 1.64 2020/03/27 00:13:52 ad Exp $     */
 
 /*-
  * Copyright (c) 2007, 2008, 2019, 2020 The NetBSD Foundation, Inc.
@@ -170,7 +170,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.63 2020/03/26 20:19:06 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.64 2020/03/27 00:13:52 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -477,6 +477,11 @@
        uintptr_t offset;
        int s;
 
+       /*
+        * If this assert fires, rather than disabling preemption explicitly
+        * to make it stop, consider that you are probably using a softint
+        * when you don't need to.
+        */     
        KASSERT(kpreempt_disabled());
 
        /* Find the handler record for this CPU. */
@@ -709,17 +714,13 @@
        si = l->l_private;
 
        for (;;) {
-               /*
-                * Clear pending status and run it.  We must drop the
-                * spl before mi_switch(), since IPL_HIGH may be higher
-                * than IPL_SCHED (and it is not safe to switch at a
-                * higher level).
-                */
+               /* Clear pending status and run it. */
                s = splhigh();
                l->l_cpu->ci_data.cpu_softints &= ~si->si_machdep;
                softint_execute(si, l, s);
                splx(s);
 
+               /* Interrupts allowed to run again before switching. */
                lwp_lock(l);
                l->l_stat = LSIDL;
                spc_lock(l->l_cpu);