Data processing apparatus and data processing method

A data processing apparatus comprising:

• a shared buffer that saves data incoming from a plurality of ports;
• an address issuing unit that when the data incoming from the ports is written to the shared buffer, issues a write address for the shared buffer from among available addresses;
• a return address receiving unit that when the data is read out from the shared buffer, receives a returned read address for the read out data and manages the returned read address as an available address;
• a monitoring buffer that saves information that indicates a use status of an address for the shared buffer;
• and
• a monitoring unit that monitors issuance of the write address by the address issuing unit and reception of the returned read address by the return address receiving unit, changes contents of the information that is saved by the monitoring buffer and corresponds to the write address to be issued, from an unused state to a used state, when the write address is issued by the address issuing unit, and changes contents of the information that is saved by the monitoring buffer and corresponds to a read address to be returned, from a used state to an unused state when the returned read address is received by the return address receiving unit, wherein
• the monitoring unit determines that the address for the shared buffer is overlapping, when the information that is saved by the monitoring buffer and corresponds to the write address to be issued indicates a used state when the write address is issued by the address issuing unit,
• the monitoring unit determines that the address for the shared buffer is overlapping, when the information that is saved by the monitoring buffer and corresponds to the read address to be returned indicates a unused state when the return address receiving unit receives the returned read address, and
• the return address receiving unit discards the read address, when the monitoring unit determines that the read address to be returned is overlapping.