Thu Jul 14 06:44:50 2016 UTC ()

Pull up following revision(s) (requested by knakahara in ticket #1356):
	sys/kern/kern_softint.c: revision 1.42
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


(snj)

diff -r1.38.8.1 -r1.38.8.1.2.1 src/sys/kern/kern_softint.c

--- src/sys/kern/kern_softint.c 2013/02/08 19:32:07	1.38.8.1
+++ src/sys/kern/kern_softint.c 2016/07/14 06:44:50	1.38.8.1.2.1

 @@ -1,14 +1,14 @@
-/*	$NetBSD: kern_softint.c,v 1.38.8.1 2013/02/08 19:32:07 riz Exp $	*/
+/*	$NetBSD: kern_softint.c,v 1.38.8.1.2.1 2016/07/14 06:44:50 snj Exp $	*/
 /*-
  * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc.
  * All rights reserved.
+ *
  * This code is derived from software contributed to The NetBSD Foundation
  * by Andrew Doran.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
 @@ -166,27 +166,27 @@
  *	If a soft interrupt handler blocks and is resumed, it resumes
  *	execution as a normal LWP (kthread) and gains VM context.  Only
  *	when it has completed and is ready to fire again will it
  *	interrupt other threads.
+ *
  * Future directions
+ *
  *	Provide a cheap way to direct software interrupts to remote
  *	CPUs.  Provide a way to enqueue work items into the handler
  *	record,	removing additional spl calls (see subr_workqueue.c).
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.38.8.1 2013/02/08 19:32:07 riz Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.38.8.1.2.1 2016/07/14 06:44:50 snj Exp $");
 #include <sys/param.h>
 #include <sys/proc.h>
 #include <sys/intr.h>
 #include <sys/mutex.h>
 #include <sys/kthread.h>
 #include <sys/evcnt.h>
 #include <sys/cpu.h>
 #include <sys/xcall.h>
 #include <sys/pserialize.h>
 #include <net/netisr.h>
 @@ -414,28 +414,28 @@ softint_disestablish(void *arg)
 	 */
 	where = xc_broadcast(0, (xcfunc_t)nullop, NULL, NULL);
 	xc_wait(where);
 	for (;;) {
 		/* Collect flag values from each CPU. */
 		flags = 0;
 		for (CPU_INFO_FOREACH(cii, ci)) {
 			sc = ci->ci_data.cpu_softcpu;
 			sh = (softhand_t *)((uint8_t *)sc + offset);
 			KASSERT(sh->sh_func != NULL);
 			flags |= sh->sh_flags;
+		}
-		/* Inactive on all CPUs? */
+		/* Neither pending nor active on all CPUs? */
-		if ((flags & SOFTINT_ACTIVE) == 0) {
+		if ((flags & (SOFTINT_PENDING | SOFTINT_ACTIVE)) == 0) {
 			break;
+		}
 		/* Oops, still active.  Wait for it to clear. */
 		(void)kpause("softdis", false, 1, NULL);
+	}
 	/* Clear the handler on each CPU. */
 	mutex_enter(&softint_lock);
 	for (CPU_INFO_FOREACH(cii, ci)) {
 		sc = ci->ci_data.cpu_softcpu;
 		sh = (softhand_t *)((uint8_t *)sc + offset);
 		KASSERT(sh->sh_func != NULL);
 		sh->sh_func = NULL;