Replace explicit rcu_read_lock/unlock with lttng::urcu::read_lock_guard

[lttng-tools.git] / src / bin / lttng-relayd / sessiond-trace-chunks.cpp

diff --git a/src/bin/lttng-relayd/sessiond-trace-chunks.cpp b/src/bin/lttng-relayd/sessiond-trace-chunks.cpp
index 1fb034053eef5bbbadd9b0940c07176a1ccae8bb..9d793c9bcf79315e722447fcb3c205f785a60c54 100644 (file)
--- a/src/bin/lttng-relayd/sessiond-trace-chunks.cpp
+++ b/src/bin/lttng-relayd/sessiond-trace-chunks.cpp
@@ -14,6 +14,7 @@
 #include <common/macros.hpp>
 #include <common/string-utils/format.hpp>
 #include <common/trace-chunk-registry.hpp>
+#include <common/urcu.hpp>
 
 #include <inttypes.h>
 #include <stdio.h>
@@ -112,9 +113,8 @@ static void trace_chunk_registry_ht_element_release(struct urcu_ref *ref)
        DBG("Destroying trace chunk registry associated to sessiond {%s}", uuid_str);
        if (element->sessiond_trace_chunk_registry) {
                /* Unpublish. */
-               rcu_read_lock();
+               lttng::urcu::read_lock_guard read_lock;
                cds_lfht_del(element->sessiond_trace_chunk_registry->ht, &element->ht_node);
-               rcu_read_unlock();
                element->sessiond_trace_chunk_registry = nullptr;
        }
 
@@ -146,7 +146,7 @@ trace_chunk_registry_ht_element_find(struct sessiond_trace_chunk_registry *sessi
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;
 
-       rcu_read_lock();
+       lttng::urcu::read_lock_guard read_lock;
        cds_lfht_lookup(sessiond_registry->ht,
                        trace_chunk_registry_ht_key_hash(key),
                        trace_chunk_registry_ht_key_match,
@@ -164,7 +164,6 @@ trace_chunk_registry_ht_element_find(struct sessiond_trace_chunk_registry *sessi
                        element = nullptr;
                }
        }
-       rcu_read_unlock();
        return element;
 }
 
@@ -198,46 +197,51 @@ trace_chunk_registry_ht_element_create(struct sessiond_trace_chunk_registry *ses
        trace_chunk_registry = nullptr;
 
        /* Attempt to publish the new element. */
-       rcu_read_lock();
-       while (true) {
-               struct cds_lfht_node *published_node;
-               struct trace_chunk_registry_ht_element *published_element;
-
-               published_node =
-                       cds_lfht_add_unique(sessiond_registry->ht,
-                                           trace_chunk_registry_ht_key_hash(&new_element->key),
-                                           trace_chunk_registry_ht_key_match,
-                                           &new_element->key,
-                                           &new_element->ht_node);
-               if (published_node == &new_element->ht_node) {
-                       /* New element published successfully. */
-                       DBG("Created trace chunk registry for sessiond {%s}", uuid_str);
-                       new_element->sessiond_trace_chunk_registry = sessiond_registry;
-                       break;
-               }
-
+       {
                /*
-                * An equivalent element was published during the creation of
-                * this element. Attempt to acquire a reference to the one that
-                * was already published and release the reference to the copy
-                * we created if successful.
+                * Keep the rcu read lock is held accross all attempts
+                * purely for efficiency reasons.
                 */
-               published_element = lttng::utils::container_of(
-                       published_node, &trace_chunk_registry_ht_element::ht_node);
-               if (trace_chunk_registry_ht_element_get(published_element)) {
-                       DBG("Acquired reference to trace chunk registry of sessiond {%s}",
-                           uuid_str);
-                       trace_chunk_registry_ht_element_put(new_element);
-                       new_element = nullptr;
-                       break;
+               lttng::urcu::read_lock_guard read_lock;
+               while (true) {
+                       struct cds_lfht_node *published_node;
+                       struct trace_chunk_registry_ht_element *published_element;
+
+                       published_node = cds_lfht_add_unique(
+                               sessiond_registry->ht,
+                               trace_chunk_registry_ht_key_hash(&new_element->key),
+                               trace_chunk_registry_ht_key_match,
+                               &new_element->key,
+                               &new_element->ht_node);
+                       if (published_node == &new_element->ht_node) {
+                               /* New element published successfully. */
+                               DBG("Created trace chunk registry for sessiond {%s}", uuid_str);
+                               new_element->sessiond_trace_chunk_registry = sessiond_registry;
+                               break;
+                       }
+
+                       /*
+                        * An equivalent element was published during the creation of
+                        * this element. Attempt to acquire a reference to the one that
+                        * was already published and release the reference to the copy
+                        * we created if successful.
+                        */
+                       published_element = lttng::utils::container_of(
+                               published_node, &trace_chunk_registry_ht_element::ht_node);
+                       if (trace_chunk_registry_ht_element_get(published_element)) {
+                               DBG("Acquired reference to trace chunk registry of sessiond {%s}",
+                                   uuid_str);
+                               trace_chunk_registry_ht_element_put(new_element);
+                               new_element = nullptr;
+                               break;
+                       }
+                       /*
+                        * A reference to the previously published element could not
+                        * be acquired. Hence, retry to publish our copy of the
+                        * element.
+                        */
                }
-               /*
-                * A reference to the previously published element could not
-                * be acquired. Hence, retry to publish our copy of the
-                * element.
-                */
        }
-       rcu_read_unlock();
 end:
        if (ret < 0) {
                ERR("Failed to create trace chunk registry for session daemon {%s}", uuid_str);