[Urgent][Stuck Problem] BLE setValue in callback function!

[JAICHANGPARK]

Hi There

Now , I'm using curie nano board
my ble program is using callback function.

void dataSyncCharCharacteristicWritten(BLEDevice central, BLECharacteristic characteristic) {
// 1. read external serial flash 
//  code here
// 2. save data in buffer from serial flash memory  
// code here 
// 3. nofity and send to application buff Value 
for (int i = 0; i < register_index; i++) {
    syncChar.setValue(syncBuff[i], SAVE_UNIT_STEP);
}
}

• where syncChar

BLECharacteristic syncChar("FFF2", BLERead | BLEWrite | BLENotify , 20);

My problem code parts is number 3
Cuire board is stuck in for statement

How to solved this problem?

regards