Show when witness(4) has run out of lock order data entries.

This makes it clearer why lock order traces are sometimes not displayed.

Prompted by a question from, and OK anton@

diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index 05a3079..9a4d3c2 100644 (file)
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: subr_witness.c,v 1.43 2021/01/09 20:59:06 gnezdo Exp $        */
+/*     $OpenBSD: subr_witness.c,v 1.44 2021/01/28 15:13:27 visa Exp $  */
 
 /*-
  * Copyright (c) 2008 Isilon Systems, Inc.
@@ -1084,6 +1084,9 @@ witness_checkorder(struct lock_object *lock, int flags,
                                            w1->w_class->lc_name);
                                        stacktrace_print(
                                            &wlod1->wlod_stack, printf);
+                               } else {
+                                       printf("lock order data "
+                                           "w2 -> w1 missing\n");
                                }
                                if (wlod2 != NULL) {
                                        printf("lock order \"%s\"(%s) -> "
@@ -1094,6 +1097,9 @@ witness_checkorder(struct lock_object *lock, int flags,
                                            w->w_class->lc_name);
                                        stacktrace_print(
                                            &wlod2->wlod_stack, printf);
+                               } else {
+                                       printf("lock order data "
+                                           "w1 -> w2 missing\n");
                                }
                        }
                        witness_debugger(0);
@@ -2436,6 +2442,7 @@ witness_lock_order_check(struct witness *parent, struct witness *child)
 static int
 witness_lock_order_add(struct witness *parent, struct witness *child)
 {
+       static int lofree_empty_reported = 0;
        struct witness_lock_order_data *data = NULL;
        struct witness_lock_order_key key;
        unsigned int hash;
@@ -2453,8 +2460,13 @@ witness_lock_order_add(struct witness *parent, struct witness *child)
            sizeof(key)) % w_lohash.wloh_size;
        w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
        data = w_lofree;
-       if (data == NULL)
+       if (data == NULL) {
+               if (!lofree_empty_reported) {
+                       lofree_empty_reported = 1;
+                       printf("witness: out of free lock order entries\n");
+               }
                return (0);
+       }
        w_lofree = data->wlod_next;
        data->wlod_next = w_lohash.wloh_array[hash];
        data->wlod_key = key;