sessiond: enforce mmap output type for kernel metadata channel

[lttng-tools.git] / src / bin / lttng-sessiond / trace-kernel.c

diff --git a/src/bin/lttng-sessiond/trace-kernel.c b/src/bin/lttng-sessiond/trace-kernel.c
index dcb1bd647b9a0a622b6cbd39c94979d1e0d30e1a..0c472c00f9188677743aac78e266ab1e786a297c 100644 (file)
--- a/src/bin/lttng-sessiond/trace-kernel.c
+++ b/src/bin/lttng-sessiond/trace-kernel.c
@@ -28,6 +28,8 @@
 
 #include <common/common.h>
 #include <common/defaults.h>
+#include <common/trace-chunk.h>
+#include <common/macros.h>
 
 #include "consumer.h"
 #include "trace-kernel.h"
@@ -38,7 +40,7 @@
  * Find the channel name for the given kernel session.
  */
 struct ltt_kernel_channel *trace_kernel_get_channel_by_name(
-               char *name, struct ltt_kernel_session *session)
+               const char *name, struct ltt_kernel_session *session)
 {
        struct ltt_kernel_channel *chan;
 
@@ -328,8 +330,8 @@ enum lttng_error_code trace_kernel_create_event(
                break;
        case LTTNG_EVENT_USERSPACE_PROBE:
        {
-               struct lttng_userspace_probe_location* location = NULL;
-               struct lttng_userspace_probe_location_lookup_method *lookup = NULL;
+               const struct lttng_userspace_probe_location* location = NULL;
+               const struct lttng_userspace_probe_location_lookup_method *lookup = NULL;
 
                location = lttng_event_get_userspace_probe_location(ev);
                if (!location) {
@@ -464,6 +466,7 @@ error:
  */
 struct ltt_kernel_metadata *trace_kernel_create_metadata(void)
 {
+       int ret;
        struct ltt_kernel_metadata *lkm;
        struct lttng_channel *chan;
 
@@ -474,13 +477,38 @@ struct ltt_kernel_metadata *trace_kernel_create_metadata(void)
                goto error;
        }
 
+       ret = lttng_strncpy(
+                       chan->name, DEFAULT_METADATA_NAME, sizeof(chan->name));
+       if (ret) {
+               ERR("Failed to initialize metadata channel name to `%s`",
+                               DEFAULT_METADATA_NAME);
+               goto error;
+       }
+
        /* Set default attributes */
-       chan->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
+       chan->attr.overwrite = DEFAULT_METADATA_OVERWRITE;
        chan->attr.subbuf_size = default_get_metadata_subbuf_size();
        chan->attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
-       chan->attr.switch_timer_interval = DEFAULT_KERNEL_CHANNEL_SWITCH_TIMER;
-       chan->attr.read_timer_interval = DEFAULT_KERNEL_CHANNEL_READ_TIMER;
-       chan->attr.output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
+       chan->attr.switch_timer_interval = DEFAULT_METADATA_SWITCH_TIMER;
+       chan->attr.read_timer_interval = DEFAULT_METADATA_READ_TIMER;;
+
+
+       /*
+        * The metadata channel of kernel sessions must use the "mmap"
+        * back-end since the consumer daemon accumulates complete
+        * metadata units before sending them to the relay daemon in
+        * live mode. The consumer daemon also needs to extract the contents
+        * of the metadata cache when computing a rotation position.
+        *
+        * In both cases, it is not possible to rely on the splice
+        * back-end as the consumer daemon may need to accumulate more
+        * content than can be backed by the ring buffer's underlying
+        * pages.
+        */
+       chan->attr.output = LTTNG_EVENT_MMAP;
+       chan->attr.tracefile_size = 0;
+       chan->attr.tracefile_count = 0;
+       chan->attr.live_timer_interval = 0;
 
        /* Init metadata */
        lkm->fd = -1;
@@ -709,7 +737,11 @@ void trace_kernel_destroy_session(struct ltt_kernel_session *session)
        cds_list_for_each_entry_safe(channel, ctmp, &session->channel_list.head, list) {
                trace_kernel_destroy_channel(channel);
        }
+}
 
+/* Free elements needed by destroy notifiers. */
+void trace_kernel_free_session(struct ltt_kernel_session *session)
+{
        /* Wipe consumer output object */
        consumer_output_put(session->consumer);