[src/trunk]: src/sys/kern Fix an assertion in _psref_held

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b63e0d1e2eee
branches:  trunk
changeset: 818741:b63e0d1e2eee
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Fri Oct 28 07:27:52 2016 +0000

description:
Fix an assertion in _psref_held

The assertion, psref->psref_lwp == curlwp, is valid only if the target
is held by the caller.

Reviewed by riastradh@

diffstat:

 sys/kern/subr_psref.c |  31 ++++++++++++++++++++-----------
 1 files changed, 20 insertions(+), 11 deletions(-)

diffs (56 lines):

diff -r 567d45085eaf -r b63e0d1e2eee sys/kern/subr_psref.c
--- a/sys/kern/subr_psref.c     Fri Oct 28 07:26:41 2016 +0000
+++ b/sys/kern/subr_psref.c     Fri Oct 28 07:27:52 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_psref.c,v 1.4 2016/04/13 08:31:00 riastradh Exp $ */
+/*     $NetBSD: subr_psref.c,v 1.5 2016/10/28 07:27:52 ozaki-r Exp $   */
 
 /*-
  * Copyright (c) 2016 The NetBSD Foundation, Inc.
@@ -64,7 +64,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_psref.c,v 1.4 2016/04/13 08:31:00 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_psref.c,v 1.5 2016/10/28 07:27:52 ozaki-r Exp $");
 
 #include <sys/types.h>
 #include <sys/condvar.h>
@@ -457,19 +457,28 @@
 
        /* Search through all the references on this CPU.  */
        LIST_FOREACH(psref, &pcpu->pcpu_head, psref_entry) {
-               /* Sanity-check the reference.  */
-               KASSERTMSG((lwp_mismatch_ok || psref->psref_lwp == curlwp),
-                   "passive reference transferred from lwp %p to lwp %p",
-                   psref->psref_lwp, curlwp);
+               /* Sanity-check the reference's CPU.  */
                KASSERTMSG((psref->psref_cpu == curcpu()),
                    "passive reference transferred from CPU %u to CPU %u",
                    cpu_index(psref->psref_cpu), cpu_index(curcpu()));
 
-               /* If it matches, stop here and answer yes.  */
-               if (psref->psref_target == target) {
-                       held = true;
-                       break;
-               }
+               /* If it doesn't match, skip it and move on.  */
+               if (psref->psref_target != target)
+                       continue;
+
+               /*
+                * Sanity-check the reference's LWP if we are asserting
+                * via psref_held that this LWP holds it, but not if we
+                * are testing in psref_target_destroy whether any LWP
+                * still holds it.
+                */
+               KASSERTMSG((lwp_mismatch_ok || psref->psref_lwp == curlwp),
+                   "passive reference transferred from lwp %p to lwp %p",
+                   psref->psref_lwp, curlwp);
+
+               /* Stop here and report that we found it.  */
+               held = true;
+               break;
        }
 
        /* Release the CPU list and restore interrupts.  */