Add rw lock to ensure metadata aren't updated while running STMT_PREPARE_RESPONSE

include/MySQL_PreparedStatement.h

@@ -42,6 +42,7 @@ class MySQL_STMT_Global_info {
 	private:
 	void compute_hash();
 	public:
+	pthread_rwlock_t rwlock_;
 	uint64_t digest;
 	MYSQL_COM_QUERY_command MyComQueryCmd;
 	char * digest_text;

lib/MySQL_PreparedStatement.cpp

@@ -136,6 +136,7 @@ MySQL_STMT_Global_info::MySQL_STMT_Global_info(uint64_t id, unsigned int h,
                                                char *u, char *s, char *q,
                                                unsigned int ql,
                                                MYSQL_STMT *stmt, uint64_t _h) {
+	pthread_rwlock_init(&rwlock_, NULL);
 	statement_id = id;
 	hostgroup_id = h;
 	ref_count_client = 0;
@@ -221,6 +222,7 @@ MySQL_STMT_Global_info::MySQL_STMT_Global_info(uint64_t id, unsigned int h,
 void MySQL_STMT_Global_info::update_metadata(MYSQL_STMT *stmt) {
 	int i;
 	bool need_refresh = false;
+	pthread_rwlock_wrlock(&rwlock_);
 	if (
 		(num_params != stmt->param_count)
 		||
@@ -400,6 +402,7 @@ void MySQL_STMT_Global_info::update_metadata(MYSQL_STMT *stmt) {
 		}
 // till here is copied from constructor
 	}
+	pthread_rwlock_unlock(&rwlock_);
 }
 
 MySQL_STMT_Global_info::~MySQL_STMT_Global_info() {

lib/MySQL_Protocol.cpp

@@ -777,6 +777,7 @@ bool MySQL_Protocol::generate_STMT_PREPARE_RESPONSE(uint8_t sequence_id, MySQL_S
 	okpack[4]=0;
 	okpack[13]=0;
 	okpack[15]=0;
+	pthread_rwlock_rdlock(&stmt_info->rwlock_);
 	if (_stmt_id) {
 		memcpy(okpack+5,&_stmt_id,sizeof(uint32_t));
 	} else {
@@ -817,6 +818,7 @@ bool MySQL_Protocol::generate_STMT_PREPARE_RESPONSE(uint8_t sequence_id, MySQL_S
 		generate_pkt_EOF(true,NULL,NULL,sid,0,setStatus);
 		sid++;
 	}
+	pthread_rwlock_unlock(&stmt_info->rwlock_);
 	return true;
 }