Dictionaries with reference counters and full deletion support during traversal (#13195)

* dont use atomic operations when not needed; detect misuse of the the unsafe functions

* use relaxed atomic operations for statistics

* use relaxed atomic operations for statistics

* dictionaries now use reference counters, allowing deletetions of any item while traversing it

* added acquire/release interface to dictionaries

* added unittest for reference counters

* added NETDATA_INTERNAL_CHECKS logs to detect non-exclusive access to crusial parts of the dictionaries

* dictionaries cannot be deleted while there are referenced items in them - they will be deleted once the last item gets unreferenced

* cleanup

* properly cleanup released items

* maintain counters for readers and writers; defer all deletes on sorted walkthrough; cleaner internal_error();

* somewhat faster reference counters on single threaded dictionaries

* minor optimizations; allow compiling without internal checks

1 files changed, 28 insertions, 29 deletions

diff --git a/daemon/global_statistics.c b/daemon/global_statistics.c
index 1d268ce81f..983bb2d7fb 100644
--- a/daemon/global_statistics.c
+++ b/daemon/global_statistics.c
@@ -46,9 +46,9 @@ static struct global_statistics {
 };
 
 void rrdr_query_completed(uint64_t db_points_read, uint64_t result_points_generated) {
-    __atomic_fetch_add(&global_statistics.rrdr_queries_made, 1, __ATOMIC_SEQ_CST);
-    __atomic_fetch_add(&global_statistics.rrdr_db_points_read, db_points_read, __ATOMIC_SEQ_CST);
-    __atomic_fetch_add(&global_statistics.rrdr_result_points_generated, result_points_generated, __ATOMIC_SEQ_CST);
+    __atomic_fetch_add(&global_statistics.rrdr_queries_made, 1, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&global_statistics.rrdr_db_points_read, db_points_read, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&global_statistics.rrdr_result_points_generated, result_points_generated, __ATOMIC_RELAXED);
 }
 
 void finished_web_request_statistics(uint64_t dt,
@@ -58,45 +58,44 @@ void finished_web_request_statistics(uint64_t dt,
                                      uint64_t compressed_content_size) {
     uint64_t old_web_usec_max = global_statistics.web_usec_max;
     while(dt > old_web_usec_max)
-        __atomic_compare_exchange(&global_statistics.web_usec_max, &old_web_usec_max, &dt, 1, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
-
-    __atomic_fetch_add(&global_statistics.web_requests, 1, __ATOMIC_SEQ_CST);
-    __atomic_fetch_add(&global_statistics.web_usec, dt, __ATOMIC_SEQ_CST);
-    __atomic_fetch_add(&global_statistics.bytes_received, bytes_received, __ATOMIC_SEQ_CST);
-    __atomic_fetch_add(&global_statistics.bytes_sent, bytes_sent, __ATOMIC_SEQ_CST);
-    __atomic_fetch_add(&global_statistics.content_size, content_size, __ATOMIC_SEQ_CST);
-    __atomic_fetch_add(&global_statistics.compressed_content_size, compressed_content_size, __ATOMIC_SEQ_CST);
+        __atomic_compare_exchange(&global_statistics.web_usec_max, &old_web_usec_max, &dt, 1, __ATOMIC_RELAXED, __ATOMIC_RELAXED);
+
+    __atomic_fetch_add(&global_statistics.web_requests, 1, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&global_statistics.web_usec, dt, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&global_statistics.bytes_received, bytes_received, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&global_statistics.bytes_sent, bytes_sent, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&global_statistics.content_size, content_size, __ATOMIC_RELAXED);
+    __atomic_fetch_add(&global_statistics.compressed_content_size, compressed_content_size, __ATOMIC_RELAXED);
 }
 
 uint64_t web_client_connected(void) {
-    __atomic_fetch_add(&global_statistics.connected_clients, 1, __ATOMIC_SEQ_CST);
-    return __atomic_fetch_add(&global_statistics.web_client_count, 1, __ATOMIC_SEQ_CST);
+    __atomic_fetch_add(&global_statistics.connected_clients, 1, __ATOMIC_RELAXED);
+    return __atomic_fetch_add(&global_statistics.web_client_count, 1, __ATOMIC_RELAXED);
 }
 
 void web_client_disconnected(void) {
-    __atomic_fetch_sub(&global_statistics.connected_clients, 1, __ATOMIC_SEQ_CST);
+    __atomic_fetch_sub(&global_statistics.connected_clients, 1, __ATOMIC_RELAXED);
 }
 
 
 static inline void global_statistics_copy(struct global_statistics *gs, uint8_t options) {
-    gs->connected_clients            = __atomic_fetch_add(&global_statistics.connected_clients, 0, __ATOMIC_SEQ_CST);
-    gs->web_requests                 = __atomic_fetch_add(&global_statistics.web_requests, 0, __ATOMIC_SEQ_CST);
-    gs->web_usec                     = __atomic_fetch_add(&global_statistics.web_usec, 0, __ATOMIC_SEQ_CST);
-    gs->web_usec_max                 = __atomic_fetch_add(&global_statistics.web_usec_max, 0, __ATOMIC_SEQ_CST);
-    gs->bytes_received               = __atomic_fetch_add(&global_statistics.bytes_received, 0, __ATOMIC_SEQ_CST);
-    gs->bytes_sent                   = __atomic_fetch_add(&global_statistics.bytes_sent, 0, __ATOMIC_SEQ_CST);
-    gs->content_size                 = __atomic_fetch_add(&global_statistics.content_size, 0, __ATOMIC_SEQ_CST);
-    gs->compressed_content_size      = __atomic_fetch_add(&global_statistics.compressed_content_size, 0, __ATOMIC_SEQ_CST);
-    gs->web_client_count             = __atomic_fetch_add(&global_statistics.web_client_count, 0, __ATOMIC_SEQ_CST);
-
-    gs->rrdr_queries_made            = __atomic_fetch_add(&global_statistics.rrdr_queries_made, 0, __ATOMIC_SEQ_CST);
-    gs->rrdr_db_points_read          = __atomic_fetch_add(&global_statistics.rrdr_db_points_read, 0, __ATOMIC_SEQ_CST);
-    gs->rrdr_result_points_generated = __atomic_fetch_add(&global_statistics.rrdr_result_points_generated, 0, __ATOMIC_SEQ_CST);
+    gs->connected_clients            = __atomic_fetch_add(&global_statistics.connected_clients, 0, __ATOMIC_RELAXED);
+    gs->web_requests                 = __atomic_fetch_add(&global_statistics.web_requests, 0, __ATOMIC_RELAXED);
+    gs->web_usec                     = __atomic_fetch_add(&global_statistics.web_usec, 0, __ATOMIC_RELAXED);
+    gs->web_usec_max                 = __atomic_fetch_add(&global_statistics.web_usec_max, 0, __ATOMIC_RELAXED);
+    gs->bytes_received               = __atomic_fetch_add(&global_statistics.bytes_received, 0, __ATOMIC_RELAXED);
+    gs->bytes_sent                   = __atomic_fetch_add(&global_statistics.bytes_sent, 0, __ATOMIC_RELAXED);
+    gs->content_size                 = __atomic_fetch_add(&global_statistics.content_size, 0, __ATOMIC_RELAXED);
+    gs->compressed_content_size      = __atomic_fetch_add(&global_statistics.compressed_content_size, 0, __ATOMIC_RELAXED);
+    gs->web_client_count             = __atomic_fetch_add(&global_statistics.web_client_count, 0, __ATOMIC_RELAXED);
+
+    gs->rrdr_queries_made            = __atomic_fetch_add(&global_statistics.rrdr_queries_made, 0, __ATOMIC_RELAXED);
+    gs->rrdr_db_points_read          = __atomic_fetch_add(&global_statistics.rrdr_db_points_read, 0, __ATOMIC_RELAXED);
+    gs->rrdr_result_points_generated = __atomic_fetch_add(&global_statistics.rrdr_result_points_generated, 0, __ATOMIC_RELAXED);
 
     if(options & GLOBAL_STATS_RESET_WEB_USEC_MAX) {
         uint64_t n = 0;
-        __atomic_compare_exchange(&global_statistics.web_usec_max, (uint64_t *) &gs->web_usec_max, &n, 1, __ATOMIC_SEQ_CST,
-                                  __ATOMIC_SEQ_CST);
+        __atomic_compare_exchange(&global_statistics.web_usec_max, (uint64_t *) &gs->web_usec_max, &n, 1, __ATOMIC_RELAXED, __ATOMIC_RELAXED);
     }
 }