From: David Goulet <dgoulet@efficios.com>
Date: Tue, 14 Jan 2014 20:44:55 +0000 (-0500)
Subject: Fix: report to client when snapshot will be empty
X-Git-Tag: v2.3.2~16
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=e9accd4fad532b481ff23af1ef2202c1b5a43c70

Fix: report to client when snapshot will be empty

This adds a new lttng error code being the "snapshot nodata".

Fixes #662

Signed-off-by: David Goulet <dgoulet@efficios.com>
---

diff --git a/include/lttng/lttng-error.h b/include/lttng/lttng-error.h
index 5e0dd07b2..817cbe8f1 100644
--- a/include/lttng/lttng-error.h
+++ b/include/lttng/lttng-error.h
@@ -101,7 +101,7 @@ enum lttng_error_code {
 	LTTNG_ERR_UST_CONSUMER64_FAIL    = 68,  /* 64-bit UST consumer start failed */
 	LTTNG_ERR_UST_CONSUMER32_FAIL    = 69,  /* 32-bit UST consumer start failed */
 	LTTNG_ERR_UST_STREAM_FAIL        = 70,  /* UST create stream failed */
-	/* 71 */
+	LTTNG_ERR_SNAPSHOT_NODATA        = 71,  /* No data in snapshot. */
 	/* 72 */
 	/* 73 */
 	LTTNG_ERR_UST_LIST_FAIL          = 74,  /* UST listing events failed */
diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index f997cc79b..cca259923 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -2637,12 +2637,17 @@ static int record_ust_snapshot(struct ltt_ust_session *usess,
 
 	ret = ust_app_snapshot_record(usess, output, wait, nb_streams);
 	if (ret < 0) {
-		if (ret == -EINVAL) {
+		switch (-ret) {
+		case EINVAL:
 			ret = LTTNG_ERR_INVALID;
-			goto error_snapshot;
+			break;
+		case ENODATA:
+			ret = LTTNG_ERR_SNAPSHOT_NODATA;
+			break;
+		default:
+			ret = LTTNG_ERR_SNAPSHOT_FAIL;
+			break;
 		}
-
-		ret = LTTNG_ERR_SNAPSHOT_FAIL;
 		goto error_snapshot;
 	}
 
diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index 315e503ed..1451963ad 100644
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -4992,6 +4992,7 @@ int ust_app_snapshot_record(struct ltt_ust_session *usess,
 		struct snapshot_output *output, int wait, unsigned int nb_streams)
 {
 	int ret = 0;
+	unsigned int snapshot_done = 0;
 	struct lttng_ht_iter iter;
 	struct ust_app *app;
 	char pathname[PATH_MAX];
@@ -5066,6 +5067,7 @@ int ust_app_snapshot_record(struct ltt_ust_session *usess,
 			if (ret < 0) {
 				goto error;
 			}
+			snapshot_done = 1;
 		}
 		break;
 	}
@@ -5133,6 +5135,7 @@ int ust_app_snapshot_record(struct ltt_ust_session *usess,
 			if (ret < 0) {
 				goto error;
 			}
+			snapshot_done = 1;
 		}
 		break;
 	}
@@ -5141,6 +5144,15 @@ int ust_app_snapshot_record(struct ltt_ust_session *usess,
 		break;
 	}
 
+	if (!snapshot_done) {
+		/*
+		 * If no snapshot was made and we are not in the error path, this means
+		 * that there are no buffers thus no (prior) application to snapshot
+		 * data from so we have simply NO data.
+		 */
+		ret = -ENODATA;
+	}
+
 error:
 	rcu_read_unlock();
 	return ret;
diff --git a/src/bin/lttng/commands/snapshot.c b/src/bin/lttng/commands/snapshot.c
index a357730d0..db5a62551 100644
--- a/src/bin/lttng/commands/snapshot.c
+++ b/src/bin/lttng/commands/snapshot.c
@@ -480,10 +480,17 @@ int cmd_snapshot(int argc, const char **argv)
 
 	ret = handle_command(poptGetArgs(pc));
 	if (ret < 0) {
-		if (ret == -LTTNG_ERR_EPERM) {
+		switch (-ret) {
+		case LTTNG_ERR_EPERM:
 			ERR("The session needs to be set in no output mode (--no-output)");
+			break;
+		case LTTNG_ERR_SNAPSHOT_NODATA:
+			WARN("%s", lttng_strerror(ret));
+			break;
+		default:
+			ERR("%s", lttng_strerror(ret));
+			break;
 		}
-		ERR("%s", lttng_strerror(ret));
 		goto end;
 	}
 
diff --git a/src/common/error.c b/src/common/error.c
index 911baea3e..5020f316a 100644
--- a/src/common/error.c
+++ b/src/common/error.c
@@ -113,6 +113,7 @@ static const char *error_string_array[] = {
 	[ ERROR_INDEX(LTTNG_ERR_SNAPSHOT_OUTPUT_EXIST) ] = "Snapshot output already exists",
 	[ ERROR_INDEX(LTTNG_ERR_START_SESSION_ONCE) ] = "Session needs to be started once",
 	[ ERROR_INDEX(LTTNG_ERR_SNAPSHOT_FAIL) ] = "Snapshot record failed",
+	[ ERROR_INDEX(LTTNG_ERR_SNAPSHOT_NODATA) ] = "No data available in snapshot",
 
 	/* Last element */
 	[ ERROR_INDEX(LTTNG_ERR_NR) ] = "Unknown error code"