IEEE Standards Interpretations for IEEE Std 1003.1c™-1995 IEEE Standard for Information Technology--Portable Operating System Interface (POSIX(R)) - System Application Program Interface (API) Amendment 2: Threads Extension (C Language)
Copyright © 1996 by the Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue New York, New York 10016-5997 USA All Rights Reserved.
Interpretations are issued to explain and clarify the intent of a standard and do not constitute an alteration to the original standard. In addition, interpretations are not intended to supply consulting information. Permission is hereby granted to download and print one copy of this document. Individuals seeking permission to reproduce and/or distribute this document in its entirety or portions of this document must contact the IEEE Standards Department for the appropriate license. Use of the information contained in this document is at your own risk.
IEEE Standards Department, Copyrights and Permissions, 445 Hoes Lane, Piscataway, New Jersey 08855-1331, USA
Interpretation Request #28
Topic: Waiting on a Condition Errors Relevant Clauses: 220.127.116.11
Clause 18.104.22.168, Waiting on a Condition Error All error conditions, except ETIMEDOUT for pthread_cond_timedwait, are reported by returning EINVAL. One of the error conditions in particular, "the mutex was not owned by the current thread at the time of the call" is an error that would be detected by unlocking the specified mutex prior to waiting. This same error is reported by pthread_mutex_unlock by returning the error EPERM. The standard should not report the same error in different places using different error codes. This error should be reported by returning EPERM for both pthread_cond_wait and pthread_cond_timedwait.
The standard is clear that pthread_cond_timedwait should report EINVAL when the mutex was not owned by the current thread at the time of the call and aconforming implementation must return that value. The interpretations committee believes that this is not what was intended and has referred the issue to the sponsor for consideration.
Rationale for Interpretation