On Fri, Mar 04, 2005 at 10:50:38AM +0900, YAMAMOTO Takashi wrote:
> > > deal with two write operations happening at once, we can just let 
> > > VOP_WRITE() not need a lock and thus we won't need the _RANGE calls. :-)
> > 
> > we can't ever do away with locking entirely for VOP_READ and VOP_WRITE,
> > since POSIX requires that for file, read() and write() must be atomic
> > with respect to each other (and write() with respect to other write()s).
> 
> really?  from susv3 (pwrite, write):
> 
> > This volume of IEEE Std 1003.1-2001 does not specify behavior of concurrent
> > writes to a file from multiple processes.

hmm, I didn't know about that, that's apparently new with SUS v3.
I'll try to dig up a specific reference to this issue in an older spec.

-Chuck