Information processing apparatus, information processing system, information processing method and control program storage medium

An information processing system, comprising:

• a processing unit that executes a search thread which searches for list-structured data and a deletion thread which deletes a data element from list-structured data;
• and
• a processing state management unit that manages execution of a plurality of threads by the processing unit, wherein
• the processing state management unit includes:
• a state holding unit that holds a maximum sequence number being an identifier given to the thread which is started lastly, a minimum sequence number being a sequence number of the thread before which all the threads ended, and sequence number management data including information indicating a start and an end of the each thread,
• a start-and-end processing unit that includes a start processing unit which gives the sequence number uniquely increased to the thread which is started, and an end processing unit which reflects completion of the thread corresponding to the sequence number in the sequence number management data, and
• an end determination unit that includes a maximum sequence number acquisition unit which acquires the maximum sequence number from the state holding unit in response to a request from the deletion thread and returns the maximum sequence number, and a minimum sequence number comparison unit which compares the maximum sequence number acquired from the deletion thread and the minimum sequence number held by the state holding unit, wherein
• calls the start processing unit at starting search processing by the search thread, and calls the end processing unit at ending search processing by the search thread, and by calling the maximum sequence number acquisition unit and the minimum sequence number comparison unit after deletion processing of the data element by the deletion thread, determines whether the data element deleted by the deletion thread is reusable or not.

An information processing method, comprising:

• giving, at starting a plurality of threads, an identifier to each thread;
• notifying, at ending of the each thread, of the end along with the identifier;
• in case that a deletion thread which deletes a data element from list-structured data being executed, maintaining a content of the deleted data element in an unmodifiable state until the ends of all threads which started before a deletion processing by the deletion thread being confirmed by a notification of the end along with the identifier;
• and
• in case that the ends of all the threads which started before the deletion processing by the deletion thread being notified of along with the identifier, putting the deleted data element into a reusable state.

A non-transitory computer-readable storage medium storing a control program causing a computer to perform:

• a processing that, at starting a plurality of threads, gives an identifier to each thread;
• a processing that, at ending the each thread, notifies of the end along with the identifier;
• a processing that, in case a deletion thread which deletes a data element from list-structured data being executed, maintaining a content of the deleted data element in an unmodifiable state until ends of all threads which started before deletion processing by the deletion thread being confirmed by a notification of the end along with the identifier;
• and
• a processing that, in case the ends of all the threads started before the deletion processing by the deletion thread is notified of along with the identifier, putting the deleted data element into a reusable state.