From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Mon, 13 May 2013 10:02:55 +0000 (-0400)
Subject: Fix: incorrect support for multi-context
X-Git-Tag: v2.2.0-rc3~24
X-Git-Url: http://git.liburcu.org/?p=lttng-ust.git;a=commitdiff_plain;h=83e43212040a26aca40a4f8fefaa3682e9edaa57

Fix: incorrect support for multi-context

* Zifei Tong <soariez@gmail.com> wrote:
> I did some debugging one this issue. The problem only occurs when we
> have more than one context field.
> So this will not work, too:
>
> lttng create
> lttng enable-event -a -u
> lttng add-context -u -t vpid
> lttng add-context -u -t vtid
> lttng start
> $@
> lttng stop
> sleep 1
> lttng view
> lttng destroy
>
> The problem I found out is wrong `fields` argument passed into
> `ustcomm_register_channel`.
> The `fields` argument passed is a pointer to the `event_field` of the
> first element in a `lttng_ctx_field` array, but not a
> `lttng_event_field` array as expected.

Fixes #529

Reported-by: Francis Giraldeau <francis.giraldeau@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/include/ust-comm.h b/include/ust-comm.h
index 133426e5..7f268b7f 100644
--- a/include/ust-comm.h
+++ b/include/ust-comm.h
@@ -48,6 +48,7 @@
 #define LTTNG_UST_COMM_REG_MSG_PADDING			64
 
 struct lttng_event_field;
+struct lttng_ctx_field;
 
 struct ustctl_reg_msg {
 	uint32_t magic;
@@ -226,7 +227,7 @@ int ustcomm_register_channel(int sock,
 	int session_objd,		/* session descriptor */
 	int channel_objd,		/* channel descriptor */
 	size_t nr_ctx_fields,
-	const struct lttng_event_field *ctx_fields,
+	const struct lttng_ctx_field *ctx_fields,
 	uint32_t *chan_id,		/* channel id (output) */
 	int *header_type); 		/* header type (output) */
 
diff --git a/liblttng-ust-comm/lttng-ust-comm.c b/liblttng-ust-comm/lttng-ust-comm.c
index 087424fe..5321922d 100644
--- a/liblttng-ust-comm/lttng-ust-comm.c
+++ b/liblttng-ust-comm/lttng-ust-comm.c
@@ -830,6 +830,47 @@ error_type:
 	return ret;
 }
 
+static
+int serialize_ctx_fields(size_t *_nr_write_fields,
+		struct ustctl_field **ustctl_fields,
+		size_t nr_fields,
+		const struct lttng_ctx_field *lttng_fields)
+{
+	struct ustctl_field *fields;
+	int i, ret;
+	size_t nr_write_fields = 0;
+
+	fields = zmalloc(nr_fields * sizeof(*fields));
+	if (!fields)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_fields; i++) {
+		struct ustctl_field *f;
+		const struct lttng_event_field *lf;
+
+		f = &fields[nr_write_fields];
+		lf = &lttng_fields[i].event_field;
+
+		/* skip 'nowrite' fields */
+		if (lf->nowrite)
+			continue;
+		strncpy(f->name, lf->name, LTTNG_UST_SYM_NAME_LEN);
+		f->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+		ret = serialize_one_type(&f->type, &lf->type);
+		if (ret)
+			goto error_type;
+		nr_write_fields++;
+	}
+
+	*_nr_write_fields = nr_write_fields;
+	*ustctl_fields = fields;
+	return 0;
+
+error_type:
+	free(fields);
+	return ret;
+}
+
 /*
  * Returns 0 on success, negative error value on error.
  */
@@ -968,7 +1009,7 @@ int ustcomm_register_channel(int sock,
 	int session_objd,		/* session descriptor */
 	int channel_objd,		/* channel descriptor */
 	size_t nr_ctx_fields,
-	const struct lttng_event_field *ctx_fields,
+	const struct lttng_ctx_field *ctx_fields,
 	uint32_t *chan_id,		/* channel id (output) */
 	int *header_type) 		/* header type (output) */
 {
@@ -982,7 +1023,7 @@ int ustcomm_register_channel(int sock,
 		struct ustcomm_notify_channel_reply r;
 	} reply;
 	size_t fields_len;
-	struct ustctl_field *fields;
+	struct ustctl_field *fields = NULL;
 	int ret;
 	size_t nr_write_fields = 0;
 
@@ -993,7 +1034,7 @@ int ustcomm_register_channel(int sock,
 
 	/* Calculate fields len, serialize fields. */
 	if (nr_ctx_fields > 0) {
-		ret = serialize_fields(&nr_write_fields, &fields,
+		ret = serialize_ctx_fields(&nr_write_fields, &fields,
 				nr_ctx_fields, ctx_fields);
 		if (ret)
 			return ret;
diff --git a/liblttng-ust/lttng-events.c b/liblttng-ust/lttng-events.c
index e4faf605..a3127a47 100644
--- a/liblttng-ust/lttng-events.c
+++ b/liblttng-ust/lttng-events.c
@@ -260,7 +260,7 @@ int lttng_session_enable(struct lttng_session *session)
 	 */
 	cds_list_for_each_entry(chan, &session->chan_head, node) {
 		const struct lttng_ctx *ctx;
-		const struct lttng_event_field *fields = NULL;
+		const struct lttng_ctx_field *fields = NULL;
 		size_t nr_fields = 0;
 		uint32_t chan_id;
 
@@ -270,7 +270,7 @@ int lttng_session_enable(struct lttng_session *session)
 		ctx = chan->ctx;
 		if (ctx) {
 			nr_fields = ctx->nr_fields;
-			fields = &ctx->fields->event_field;
+			fields = ctx->fields;
 		}
 		ret = ustcomm_register_channel(notify_socket,
 			session->objd,