[src/trunk]: src/sys/kern Add a new sanity check to psref

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

details:   https://anonhg.NetBSD.org/src/rev/8420101b73ab
branches:  trunk
changeset: 348813:8420101b73ab
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Wed Nov 09 09:00:46 2016 +0000

description:
Add a new sanity check to psref

It checks if a target being acquired is already acquired with
the same psref. It is usable but not lightweight, so enabled
only if DEBUG.

diffstat:

 sys/kern/subr_psref.c |  31 +++++++++++++++++++++++++++++--
 1 files changed, 29 insertions(+), 2 deletions(-)

diffs (59 lines):

diff -r 634b4c884480 -r 8420101b73ab sys/kern/subr_psref.c
--- a/sys/kern/subr_psref.c     Wed Nov 09 08:18:56 2016 +0000
+++ b/sys/kern/subr_psref.c     Wed Nov 09 09:00:46 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_psref.c,v 1.5 2016/10/28 07:27:52 ozaki-r Exp $   */
+/*     $NetBSD: subr_psref.c,v 1.6 2016/11/09 09:00:46 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 1.5 2016/10/28 07:27:52 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_psref.c,v 1.6 2016/11/09 09:00:46 ozaki-r Exp $");
 
 #include <sys/types.h>
 #include <sys/condvar.h>
@@ -195,6 +195,28 @@
        target->prt_draining = false;
 }
 
+#ifdef DEBUG
+static void
+psref_check_duplication(struct psref_cpu *pcpu, struct psref *psref,
+    const struct psref_target *target)
+{
+       bool found = false;
+       struct psref *_psref;
+
+       LIST_FOREACH(_psref, &pcpu->pcpu_head, psref_entry) {
+               if (_psref == psref &&
+                   _psref->psref_target == target) {
+                       found = true;
+                       break;
+               }
+       }
+       if (found) {
+               panic("trying to acquire a target twice with the same psref: "
+                   "psref=%p target=%p", psref, target);
+       }
+}
+#endif /* DEBUG */
+
 /*
  * psref_acquire(psref, target, class)
  *
@@ -231,6 +253,11 @@
        s = splraiseipl(class->prc_iplcookie);
        pcpu = percpu_getref(class->prc_percpu);
 
+#ifdef DEBUG
+       /* Sanity-check if the target is already acquired with the same psref.  */
+       psref_check_duplication(pcpu, psref, target);
+#endif
+
        /* Record our reference.  */
        LIST_INSERT_HEAD(&pcpu->pcpu_head, psref, psref_entry);
        psref->psref_target = target;