Author: markj
Date: Fri Aug 16 15:31:46 2019
New Revision: 351126
URL: https://svnweb.freebsd.org/changeset/base/351126
Log:
MFC r350450, r350540:
Enable witness(4) blessings.
Modified:
stable/12/sys/kern/subr_witness.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/kern/subr_witness.c
==============================================================================
--- stable/12/sys/kern/subr_witness.c Fri Aug 16 15:25:53 2019
(r351125)
+++ stable/12/sys/kern/subr_witness.c Fri Aug 16 15:31:46 2019
(r351126)
@@ -132,9 +132,6 @@ __FBSDID("$FreeBSD$");
#define LI_EXCLUSIVE 0x00010000 /* Exclusive lock instance. */
#define LI_NORELEASE 0x00020000 /* Lock not allowed to be
released. */
-/* Define this to check for blessed mutexes */
-#undef BLESSING
-
#ifndef WITNESS_COUNT
#define WITNESS_COUNT 1536
#endif
@@ -278,12 +275,10 @@ struct witness_lock_order_hash {
u_int wloh_count;
};
-#ifdef BLESSING
struct witness_blessed {
const char *b_lock1;
const char *b_lock2;
};
-#endif
struct witness_pendhelp {
const char *wh_type;
@@ -318,9 +313,7 @@ witness_lock_order_key_equal(const struct witness_lock
static int _isitmyx(struct witness *w1, struct witness *w2, int rmask,
const char *fname);
static void adopt(struct witness *parent, struct witness *child);
-#ifdef BLESSING
static int blessed(struct witness *, struct witness *);
-#endif
static void depart(struct witness *w);
static struct witness *enroll(const char *description,
struct lock_class *lock_class);
@@ -727,14 +720,25 @@ static struct witness_order_list_entry order_lists[] =
{ NULL, NULL }
};
-#ifdef BLESSING
/*
- * Pairs of locks which have been blessed
- * Don't complain about order problems with blessed locks
+ * Pairs of locks which have been blessed. Witness does not complain about
+ * order problems with blessed lock pairs. Please do not add an entry to the
+ * table without an explanatory comment.
*/
static struct witness_blessed blessed_list[] = {
+ /*
+ * See the comment in ufs_dirhash.c. Basically, a vnode lock serializes
+ * both lock orders, so a deadlock cannot happen as a result of this
+ * LOR.
+ */
+ { "dirhash", "bufwait" },
+
+ /*
+ * A UFS vnode may be locked in vget() while a buffer belonging to the
+ * parent directory vnode is locked.
+ */
+ { "ufs", "bufwait" },
};
-#endif
/*
* This global is set to 0 once it becomes safe to use the witness code.
@@ -1340,17 +1344,7 @@ witness_checkorder(struct lock_object *lock, int flags
* We have a lock order violation, check to see if it
* is allowed or has already been yelled about.
*/
-#ifdef BLESSING
- /*
- * If the lock order is blessed, just bail. We don't
- * look for other lock order violations though, which
- * may be a bug.
- */
- if (blessed(w, w1))
- goto out;
-#endif
-
/* Bail if this violation is known */
if (w_rmatrix[w1->w_index][w->w_index] &
WITNESS_REVERSAL)
goto out;
@@ -1360,6 +1354,14 @@ witness_checkorder(struct lock_object *lock, int flags
w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
w->w_reversed = w1->w_reversed = 1;
witness_increment_graph_generation();
+
+ /*
+ * If the lock order is blessed, bail before logging
+ * anything. We don't look for other lock order
+ * violations though, which may be a bug.
+ */
+ if (blessed(w, w1))
+ goto out;
mtx_unlock_spin(&w_mtx);
#ifdef WITNESS_NO_VNODE
@@ -2085,7 +2087,6 @@ isitmydescendant(struct witness *ancestor, struct witn
__func__));
}
-#ifdef BLESSING
static int
blessed(struct witness *w1, struct witness *w2)
{
@@ -2105,7 +2106,6 @@ blessed(struct witness *w1, struct witness *w2)
}
return (0);
}
-#endif
static struct witness *
witness_get(void)
@@ -2651,6 +2651,9 @@ restart:
&tmp_data2->wlod_stack);
}
mtx_unlock_spin(&w_mtx);
+
+ if (blessed(tmp_w1, tmp_w2))
+ continue;
sbuf_printf(sb,
"\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
_______________________________________________
[email protected] mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "[email protected]"
