Add a HT to lookup sessions by id

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-sessiond/session.c b/src/bin/lttng-sessiond/session.c
index 1e5a81831c978451b0df61ad19712eea3a3c3fac..a6281662cf63c23e67b1172b6930e47af3094d10 100644 (file)
--- a/src/bin/lttng-sessiond/session.c
+++ b/src/bin/lttng-sessiond/session.c
@@ -30,6 +30,7 @@
 #include <common/sessiond-comm/sessiond-comm.h>
 
 #include "session.h"
+#include "utils.h"
 
 /*
  * NOTES:
@@ -54,6 +55,9 @@ static struct ltt_session_list ltt_session_list = {
 /* These characters are forbidden in a session name. Used by validate_name. */
 static const char *forbidden_name_chars = "/";
 
+/* Global hash table to keep the sessions, indexed by id. */
+static struct lttng_ht *ltt_sessions_ht_by_id = NULL;
+
 /*
  * Validate the session name for forbidden characters.
  *
@@ -137,6 +141,103 @@ void session_unlock_list(void)
        pthread_mutex_unlock(&ltt_session_list.lock);
 }
 
+/*
+ * Allocate the ltt_sessions_ht_by_id HT.
+ */
+int ltt_sessions_ht_alloc(void)
+{
+       int ret = 0;
+
+       DBG("Allocating ltt_sessions_ht_by_id");
+       ltt_sessions_ht_by_id = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       if (!ltt_sessions_ht_by_id) {
+               ret = -1;
+               ERR("Failed to allocate ltt_sessions_ht_by_id");
+               goto end;
+       }
+end:
+       return ret;
+}
+
+/*
+ * Destroy the ltt_sessions_ht_by_id HT.
+ */
+void ltt_sessions_ht_destroy(void)
+{
+       if (!ltt_sessions_ht_by_id) {
+               return;
+       }
+       ht_cleanup_push(ltt_sessions_ht_by_id);
+       ltt_sessions_ht_by_id = NULL;
+}
+
+/*
+ * Add a ltt_session to the ltt_sessions_ht_by_id.
+ * If unallocated, the ltt_sessions_ht_by_id HT is allocated.
+ * The session list lock must be held.
+ */
+static void add_session_ht(struct ltt_session *ls)
+{
+       int ret;
+
+       assert(ls);
+
+       if (!ltt_sessions_ht_by_id) {
+               ret = ltt_sessions_ht_alloc();
+               if (ret) {
+                       ERR("Error allocating the sessions HT");
+                       goto end;
+               }
+       }
+       lttng_ht_node_init_u64(&ls->node, ls->id);
+       lttng_ht_add_unique_u64(ltt_sessions_ht_by_id, &ls->node);
+
+end:
+       return;
+}
+
+/*
+ * Test if ltt_sessions_ht_by_id is empty.
+ * Return 1 if empty, 0 if not empty.
+ * The session list lock must be held.
+ */
+static int ltt_sessions_ht_empty()
+{
+       int ret;
+
+       if (!ltt_sessions_ht_by_id) {
+               ret = 1;
+               goto end;
+       }
+
+       ret = lttng_ht_get_count(ltt_sessions_ht_by_id) ? 0 : 1;
+end:
+       return ret;
+}
+
+/*
+ * Remove a ltt_session from the ltt_sessions_ht_by_id.
+ * If empty, the ltt_sessions_ht_by_id HT is freed.
+ * The session list lock must be held.
+ */
+static void del_session_ht(struct ltt_session *ls)
+{
+       struct lttng_ht_iter iter;
+       int ret;
+
+       assert(ls);
+       assert(ltt_sessions_ht_by_id);
+
+       iter.iter.node = &ls->node.node;
+       ret = lttng_ht_del(ltt_sessions_ht_by_id, &iter);
+       assert(!ret);
+
+       if (ltt_sessions_ht_empty()) {
+               DBG("Empty ltt_sessions_ht_by_id, destroying it");
+               ltt_sessions_ht_destroy();
+       }
+}
+
 /*
  * Acquire session lock
  */
@@ -159,7 +260,7 @@ void session_unlock(struct ltt_session *session)
 
 /*
  * Return a ltt_session structure ptr that matches name. If no session found,
- * NULL is returned. This must be called with the session lock held using
+ * NULL is returned. This must be called with the session list lock held using
  * session_lock_list and session_unlock_list.
  */
 struct ltt_session *session_find_by_name(const char *name)
@@ -182,6 +283,32 @@ found:
        return iter;
 }
 
+/*
+ * Return an ltt_session that matches the id. If no session is found,
+ * NULL is returned. This must be called with rcu_read_lock and
+ * session list lock held (to guarantee the lifetime of the session).
+ */
+struct ltt_session *session_find_by_id(uint64_t id)
+{
+       struct lttng_ht_node_u64 *node;
+       struct lttng_ht_iter iter;
+       struct ltt_session *ls;
+
+       lttng_ht_lookup(ltt_sessions_ht_by_id, &id, &iter);
+       node = lttng_ht_iter_get_node_u64(&iter);
+       if (node == NULL) {
+               goto error;
+       }
+       ls = caa_container_of(node, struct ltt_session, node);
+
+       DBG3("Session %" PRIu64 " found by id.", id);
+       return ls;
+
+error:
+       DBG3("Session %" PRIu64 " NOT found by id", id);
+       return NULL;
+}
+
 /*
  * Delete session from the session list and free the memory.
  *
@@ -196,6 +323,7 @@ int session_destroy(struct ltt_session *session)
        DBG("Destroying session %s", session->name);
        del_session_list(session);
        pthread_mutex_destroy(&session->lock);
+       del_session_ht(session);
 
        consumer_output_put(session->consumer);
        snapshot_destroy(&session->snapshot);
@@ -267,13 +395,19 @@ int session_create(char *name, uid_t uid, gid_t gid)
        /* Add new session to the session list */
        session_lock_list();
        new_session->id = add_session_list(new_session);
+       /*
+        * Add the new session to the ltt_sessions_ht_by_id.
+        * No ownership is taken by the hash table; it is merely
+        * a wrapper around the session list used for faster access
+        * by session id.
+        */
+       add_session_ht(new_session);
        session_unlock_list();
 
        /*
         * Consumer is let to NULL since the create_session_uri command will set it
         * up and, if valid, assign it to the session.
         */
-
        DBG("Tracing session %s created with ID %" PRIu64 " by UID %d GID %d",
                        name, new_session->id, new_session->uid, new_session->gid);
 

diff --git a/src/bin/lttng-sessiond/session.h b/src/bin/lttng-sessiond/session.h
index 48dc44a33d632efaff87598d1057f7569b83e584..77f0bf7b1ee87ac4a7b7cd43c731ca0d63701ac4 100644 (file)
--- a/src/bin/lttng-sessiond/session.h
+++ b/src/bin/lttng-sessiond/session.h
@@ -113,6 +113,10 @@ struct ltt_session {
         * Path where to keep the shared memory files.
         */
        char shm_path[PATH_MAX];
+       /*
+        * Node in ltt_sessions_ht_by_id.
+        */
+       struct lttng_ht_node_u64 node;
 };
 
 /* Prototypes */
@@ -125,6 +129,7 @@ void session_unlock(struct ltt_session *session);
 void session_unlock_list(void);
 
 struct ltt_session *session_find_by_name(const char *name);
+struct ltt_session *session_find_by_id(uint64_t id);
 struct ltt_session_list *session_get_list(void);
 
 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid);

diff --git a/tests/unit/test_session.c b/tests/unit/test_session.c
index bb136a022eb12b0862aaa336fe9811db3aab51df..7c925908d326f18443c3e2184a50a8c430abb723 100644 (file)
--- a/tests/unit/test_session.c
+++ b/tests/unit/test_session.c
@@ -108,8 +108,7 @@ static void empty_session_list(void)
        struct ltt_session *iter, *tmp;
 
        cds_list_for_each_entry_safe(iter, tmp, &session_list->head, list) {
-               cds_list_del(&iter->list);
-               free(iter);
+               session_destroy(iter);
        }
 
        /* Session list must be 0 */