Avoid interleaving of mutexes that would leave is with the wrong spl after

calling bufq_quiesce().  Problem spotted by matthew@.

ok matthew@, thib@

diff --git a/sys/kern/kern_bufq.c b/sys/kern/kern_bufq.c
index 31b6963..e59cac2 100644 (file)
--- a/sys/kern/kern_bufq.c
+++ b/sys/kern/kern_bufq.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kern_bufq.c,v 1.13 2010/07/08 23:18:55 dlg Exp $      */
+/*     $OpenBSD: kern_bufq.c,v 1.14 2010/07/19 21:39:15 kettenis Exp $ */
 /*
  * Copyright (c) 2010 Thordur I. Bjornsson <thib@openbsd.org>
  *
@@ -27,7 +27,7 @@
 #include <sys/disklabel.h>
 
 SLIST_HEAD(, bufq)     bufqs = SLIST_HEAD_INITIALIZER(&bufq);
-struct mutex           bufqs_mtx = MUTEX_INITIALIZER(IPL_BIO);
+struct mutex           bufqs_mtx = MUTEX_INITIALIZER(IPL_NONE);
 int                    bufqs_stop;
 
 struct buf *(*bufq_dequeuev[BUFQ_HOWMANY])(struct bufq *, int) = {
@@ -71,6 +71,9 @@ bufq_init(int type)
        KASSERT(error == 0);
 
        mtx_enter(&bufqs_mtx);
+       while (bufqs_stop) {
+               msleep(&bufqs_stop, &bufqs_mtx, PRIBIO, "bqinit", 0);
+       }
        SLIST_INSERT_HEAD(&bufqs, bq, bufq_entries);
        mtx_leave(&bufqs_mtx);
 
@@ -87,7 +90,7 @@ bufq_destroy(struct bufq *bq)
 
        mtx_enter(&bufqs_mtx);
        while (bufqs_stop) {
-               msleep(&bufqs_stop, &bufqs_mtx, PRIBIO, "bufqstop", 0);
+               msleep(&bufqs_stop, &bufqs_mtx, PRIBIO, "bqdest", 0);
        }
        SLIST_REMOVE(&bufqs, bq, bufq, bufq_entries);
        mtx_leave(&bufqs_mtx);
@@ -100,7 +103,7 @@ bufq_queue(struct bufq *bq, struct buf *bp)
 {
        mtx_enter(&bq->bufq_mtx);
        while (bq->bufq_stop) {
-               msleep(&bq->bufq_stop, &bq->bufq_mtx, PRIBIO, "bufqstop", 0);
+               msleep(&bq->bufq_stop, &bq->bufq_mtx, PRIBIO, "bqqueue", 0);
        }
        bufq_queuev[bq->bufq_type](bq, bp);
        mtx_leave(&bq->bufq_mtx);
@@ -146,21 +149,18 @@ bufq_quiesce(void)
 {
        struct bufq             *bq;
 
-restart:
        mtx_enter(&bufqs_mtx);
        bufqs_stop = 1;
+       mtx_leave(&bufqs_mtx);
        SLIST_FOREACH(bq, &bufqs, bufq_entries) {
                mtx_enter(&bq->bufq_mtx);
                bq->bufq_stop = 1;
-               if (bq->bufq_outstanding) {
-                       mtx_leave(&bufqs_mtx);
+               while (bq->bufq_outstanding) {
                        msleep(&bq->bufq_outstanding, &bq->bufq_mtx,
-                           PRIBIO | PNORELOCK, "bufqqui", 0);
-                       goto restart;
+                           PRIBIO, "bqquies", 0);
                }
                mtx_leave(&bq->bufq_mtx);
        }
-       mtx_leave(&bufqs_mtx);
 }
 
 void