see http://www.apache.org/~trawick/PR20295/pipes_are_not_atomic.patch and http://nagoya.apache.org/bugzilla/show_bug.cgi?id=20295
apr_file_write() and its callers are not properly dealing with the atomic nature of some pipe write operations on Unix-ish systems. I suggest that it is reasonable to drop any promise that such operations were atomic (if indeed any promise was ever made), and that the most practical solution can then be implemented.
Attempting to preserve the Unix behavior that a write for <= PIPE_BUF bytes will only work if the entire "message" can be written has a less clear and less efficient solution to the current breakage.
