fix: incorrect shared memory setup

Before the shared memory wasn't guarded with lwlocks plus there was no
call to RequestAddinShmemSpace to estimate used memory.

Closes #220

Author: steve-chavez

src/pg_prelude.h

@@ -47,6 +47,8 @@
 
 #pragma GCC diagnostic pop
 
+#define PG15_GTE (PG_VERSION_NUM >= 150000)
+
 const char *xact_event_name(XactEvent event);
 #endif /* PG_PRELUDE_H */
 

src/worker.c

@@ -37,6 +37,11 @@ static int                      guc_batch_size;
 static char*                    guc_database_name;
 static char*                    guc_username;
 static MemoryContext            CurlMemContext = NULL;
+
+#if PG15_GTE
+static shmem_request_hook_type  prev_shmem_request_hook = NULL;
+#endif
+
 static shmem_startup_hook_type  prev_shmem_startup_hook = NULL;
 static volatile sig_atomic_t    got_sighup = false;
 
@@ -357,12 +362,27 @@ void pg_net_worker(__attribute__ ((unused)) Datum main_arg) {
   proc_exit(EXIT_FAILURE);
 }
 
+static Size net_memsize(void) {
+  return MAXALIGN(sizeof(WorkerState));
+}
+
+#if PG15_GTE
+static void net_shmem_request(void) {
+  if (prev_shmem_request_hook)
+    prev_shmem_request_hook();
+
+  RequestAddinShmemSpace(net_memsize());
+}
+#endif
+
 static void net_shmem_startup(void) {
   if (prev_shmem_startup_hook)
     prev_shmem_startup_hook();
 
   bool found;
 
+  LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
+
   worker_state = ShmemInitStruct("pg_net worker state", sizeof(WorkerState), &found);
 
   if (!found) {
@@ -375,6 +395,8 @@ static void net_shmem_startup(void) {
     worker_state->epfd = 0;
     worker_state->curl_mhandle = NULL;
   }
+
+  LWLockRelease(AddinShmemInitLock);
 }
 
 void _PG_init(void) {
@@ -397,6 +419,13 @@ void _PG_init(void) {
     .bgw_restart_time = net_worker_restart_time_sec,
   });
 
+#if PG15_GTE
+  prev_shmem_request_hook = shmem_request_hook;
+  shmem_request_hook = net_shmem_request;
+#else
+  RequestAddinShmemSpace(net_memsize());
+#endif
+
   prev_shmem_startup_hook = shmem_startup_hook;
   shmem_startup_hook = net_shmem_startup;