ddb(4): Add 'show badstacks' command to show witness badstacks

Add a DDB command that mirrors sysctl debug.witness.badstacks.

Reported by:	rstone
Reviewed by:	rstone
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D12468

1 files changed, 45 insertions, 16 deletions

diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index be3ca31df356..dffbb3afbae6 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -2539,31 +2539,18 @@ DB_SHOW_COMMAND(witness, db_witness_display)
 }
 #endif
 
-static int
-sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
+static void
+sbuf_print_witness_badstacks(struct sbuf *sb)
 {
 	struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
 	struct witness *tmp_w1, *tmp_w2, *w1, *w2;
-	struct sbuf *sb;
 	u_int w_rmatrix1, w_rmatrix2;
-	int error, generation, i, j;
+	int generation, i, j;
 
 	tmp_data1 = NULL;
 	tmp_data2 = NULL;
 	tmp_w1 = NULL;
 	tmp_w2 = NULL;
-	if (witness_watch < 1) {
-		error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
-		return (error);
-	}
-	if (witness_cold) {
-		error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
-		return (error);
-	}
-	error = 0;
-	sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
-	if (sb == NULL)
-		return (ENOMEM);
 
 	/* Allocate and init temporary storage space. */
 	tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
@@ -2683,6 +2670,28 @@ restart:
 	free(tmp_data2, M_TEMP);
 	free(tmp_w1, M_TEMP);
 	free(tmp_w2, M_TEMP);
+}
+
+static int
+sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
+{
+	struct sbuf *sb;
+	int error;
+
+	if (witness_watch < 1) {
+		error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
+		return (error);
+	}
+	if (witness_cold) {
+		error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
+		return (error);
+	}
+	error = 0;
+	sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
+	if (sb == NULL)
+		return (ENOMEM);
+
+	sbuf_print_witness_badstacks(sb);
 
 	sbuf_finish(sb);
 	error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
@@ -2691,6 +2700,26 @@ restart:
 	return (error);
 }
 
+#ifdef DDB
+static int
+sbuf_db_printf_drain(void *arg __unused, const char *data, int len)
+{
+
+	return (db_printf("%.*s", len, data));
+}
+
+DB_SHOW_COMMAND(badstacks, db_witness_badstacks)
+{
+	struct sbuf sb;
+	char buffer[128];
+
+	sbuf_new(&sb, buffer, sizeof(buffer), SBUF_FIXEDLEN);
+	sbuf_set_drain(&sb, sbuf_db_printf_drain, NULL);
+	sbuf_print_witness_badstacks(&sb);
+	sbuf_finish(&sb);
+}
+#endif
+
 static int
 sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS)
 {