I've asked a similar question to this previously, but the comments I got make me think I didn't express myself well or something, so I deleted it and will try again. I have C code that is using libaio asynchronous I/O threads to write to a file. Later in the code, the memory locations that are being written are re-populated. Needless to say, I have to make sure the writing is complete before the re-populating starts. If I call fsync() before the re-population starts, will this cause the main thread to block until the writing from all threads are complete? The fsync man page seems to imply this, but I can't find a clear statement of it. There is also the aio_fsync function, but its man page says that "Note that this is a request only; it does not wait for I/O completion." But waiting for I/O completion is exactly what I need.
I know that I can check on all threads writing to said file, one by one, and wait until they are done. But I was hoping for a one-liner like just calling fsync(). Is there such a thing?