[src/trunk]: src/sys/kern fix the following softint parallel operation problem.

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

details:   https://anonhg.NetBSD.org/src/rev/eaaf2223184c
branches:  trunk
changeset: 342482:eaaf2223184c
user:      knakahara <knakahara%NetBSD.org@localhost>
date:      Thu Dec 24 02:27:14 2015 +0000

description:
fix the following softint parallel operation problem.

(0) softint handler "handler A" is established
(1) CPU#X does softint_schedule() for "handler A"
    - the softhand_t is set SOFTINT_PENDING flag
    - the softhand_t is NOT set SOFTINT_ACTIVE flag yet
(2) CPU#X begins other H/W interrupt processing
(3) CPU#Y does softint_disestablish() for "handler A"
    - waits until softhand_t's SOFTINT_ACTIVE of all CPUs is clear
    - the softhand_t is set not SOFTINT_ACTIVE but SOFTINT_PENDING,
      so CPU#Y does not wait
    - unset the function of "handler A"
(4) CPU#X does softint_execute()
    - the function of "handler A" is already clear, so panic

diffstat:

 sys/kern/kern_softint.c |  8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diffs (29 lines):

diff -r c5aaac9797de -r eaaf2223184c sys/kern/kern_softint.c
--- a/sys/kern/kern_softint.c   Thu Dec 24 01:41:27 2015 +0000
+++ b/sys/kern/kern_softint.c   Thu Dec 24 02:27:14 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_softint.c,v 1.41 2014/05/25 15:42:01 rmind Exp $  */
+/*     $NetBSD: kern_softint.c,v 1.42 2015/12/24 02:27:14 knakahara Exp $      */
 
 /*-
  * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc.
@@ -170,7 +170,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.41 2014/05/25 15:42:01 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.42 2015/12/24 02:27:14 knakahara Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -442,8 +442,8 @@
                        KASSERT(sh->sh_func != NULL);
                        flags |= sh->sh_flags;
                }
-               /* Inactive on all CPUs? */
-               if ((flags & SOFTINT_ACTIVE) == 0) {
+               /* Neither pending nor active on all CPUs? */
+               if ((flags & (SOFTINT_PENDING | SOFTINT_ACTIVE)) == 0) {
                        break;
                }
                /* Oops, still active.  Wait for it to clear. */