#13525: hWaitForInput with timeout causes program to abort ----------------------------------+-------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.2 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #12912, #8684 | Differential Rev(s): Wiki Page: | ----------------------------------+-------------------------------------- Comment (by Ben Gamari ): In [changeset:"3d523fd990bbb31ca97ea22059ec9d53f0705d8c/ghc" 3d523fd9/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="3d523fd990bbb31ca97ea22059ec9d53f0705d8c" base: Add test for #13525 Reviewers: austin, hvr Subscribers: rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3419 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13525#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13525: hWaitForInput with timeout causes program to abort ----------------------------------+-------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.0.2 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #12912, #8684 | Differential Rev(s): Wiki Page: | ----------------------------------+-------------------------------------- Comment (by bgamari): One approach to fix for the threaded runtime this would be to use `threadWaitRead` in conjunction with `System.timeout`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13525#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13525: hWaitForInput with timeout causes program to abort ----------------------------------+-------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: patch Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.0.2 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #12912, #8684 | Differential Rev(s): Phab:D3473 Wiki Page: | ----------------------------------+-------------------------------------- Changes (by bgamari): * status: new => patch * differential: => Phab:D3473 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13525#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13525: hWaitForInput with timeout causes program to abort ----------------------------------+-------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: merge Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.0.2 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #12912, #8684 | Differential Rev(s): Phab:D3473 Wiki Page: | ----------------------------------+-------------------------------------- Changes (by bgamari): * status: patch => merge Comment: Merged to `ghc-8.2` as 91c4e6b6531db59b0cd4386cf0ba8f9db35728ba. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13525#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13525: hWaitForInput with timeout causes program to abort ----------------------------------+-------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: closed Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.0.2 Resolution: fixed | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: 8684 Related Tickets: #12912, #8684 | Differential Rev(s): Phab:D3473 Wiki Page: | ----------------------------------+-------------------------------------- Comment (by Ben Gamari ): In [changeset:"ba4dcc7cb77a37486368911fec854d112a1db93c/ghc" ba4dcc7c/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="ba4dcc7cb77a37486368911fec854d112a1db93c" base: Make it less likely for fdReady() to fail on Windows sockets. See the added comment for details. It's "less likely" because it can still fail if the socket happens to have an FD larger than 1023, which can happen if many files are opened. Until now, basic socket programs that use `hWaitForInput` were broken on Windows. That is because on Windows `FD_SETSIZE` defaults to 64, but pretty much all GHC programs seem to have > 64 FDs open, so you can't actually create a socket on which you can `select()`. It errors with `fdReady: fd is too big` even with an example as simple as the following (in this case, on my machine the `fd` is `284`): {-# LANGUAGE OverloadedStrings #-} import Control.Monad (forever) import Network.Socket import System.IO -- Simple echo server: Reads up to 10 chars from network, echoes them back. -- Uses the Handle API so that `hWaitForInput` can be used. main :: IO () main = do sock <- socket AF_INET Stream 0 setSocketOption sock ReuseAddr 1 bind sock (SockAddrInet 1234 0x0100007f) -- 0x0100007f == 127.0.0.1 localhost listen sock 2 forever $ do (connSock, _connAddr) <- accept sock putStrLn "Got connection" h <- socketToHandle connSock ReadWriteMode hSetBuffering h NoBuffering ready <- hWaitForInput h (5 * 1000) -- 5 seconds putStrLn $ "Ready: " ++ show ready line <- hGetLine h putStrLn "Got line" hPutStrLn h ("Got: " ++ line) hClose h I'm not sure how this was not discovered earlier; for #13525 (where `fdReady()` breaking completely was also discovered late) at least it failed only when the timeout was non-zero, which is not used in ghc beyond in `hWaitForInput`, but in this Windows socket case it breaks even on the 0-timeout. Maybe there is not actually anybody who uses sockets as handles on Windows? The workaround for now is to increase `FD_SETSIZE` on Windows; increasing it is possible on Windows and BSD, see https://stackoverflow.com/questions/7976388/increasing-limit-of-fd-setsi ze-and-select A real fix would be to move to IO Completion Ports on Windows, and thus get rid of the last uses of `select()` (the other platforms already use `poll()` but Windows doesn't have that). Reviewers: bgamari, austin, hvr, erikd, simonmar Reviewed By: bgamari Subscribers: rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3959 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13525#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler