On Mon, Mar 17, 2008 at 2:29 AM, Vitaliy Akimov
Hi Adam, sorry for late answer. Here is my example [1], but yours doesn't work on my PC too. And it's strange it works on yours.
Are you running Windows? Because you're hpaste example works, nonblocking for me too.
And after changing in the network package FFI declaration for c_recvfrom from unsafe to safe both examples start working.
The important point here is that the recvFrom calls in Network.Socket[1] don't block. They are non-blocking calls so, although other threads may be suspended while in the FFI call, the FFI call returns -EAGAIN if it would block and blocking is passed to the RTS to handle. While sleeping in the RTS (with threadWaitRead etc), other Haskell threads can read. See the code in [1] (esp throwErrnoIfMinus1Retry_repeatOnBlock) So, the only reason that other threads would be blocked is if the socket wasn't marked as non-blocking. Here's a snippet of strace output from compiling your hpaste example: socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 5 fcntl64(5, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(5, F_SETFL, O_RDWR|O_NONBLOCK) = 0 You can see that the socket is set to non-blocking immediately. [1] http://haskell.org/ghc/docs/latest/html/libraries/network/src/Network-Socket... -- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org