On Thu, Mar 29, 2007 at 10:55:43AM +0100, Simon Marlow wrote:
Bryan O'Sullivan wrote:
John Goerzen wrote:
And strace shows that, sure enough, read(0,...) in grep is getting EAGAIN.
Sounds like somebody forgot to take the fd out of non-blocking mode.
Yep, that looks like what's happening. See System/Process/Internals.hs:runProcessPosix. I wonder why the lower-level runProcess that it calls is written in C.
We can't just take a file descriptor out of non-blocking mode, because due to broken POSIX semantics that would screw up GHC's use of the file descriptor (there's no way to set non-blocking mode per-FD). We can "fix"
See fcntl(2) -- F_SETFL can change the O_NONBLOCK flag. I don't think this should be a problem for the RTS since it can be done only on the endpoint of the pipe that is used post-fork. -- John