Commit 794c3863 authored by Petr Pudlak's avatar Petr Pudlak

When forking a job, close all unnecessary file descriptors

This is a bit problematic as there is no portable way how to list all
open file descriptors, and we can't track them all, because they're also
opened by third party libraries such as inotify. Therefore we use
/proc/self/fd and /dev/fd, which should work for all Linux flavors and
most *BSD as well. If both are missing, we don't do anything and just
log a warning.
Signed-off-by: default avatarPetr Pudlak <>
Reviewed-by: default avatarKlaus Aehlig <>
parent f40023d4
......@@ -55,11 +55,15 @@ import Control.Concurrent
import Control.Exception.Lifted (finally)
import Control.Monad
import Control.Monad.Error
import Data.Functor
import qualified Data.Map as M
import Data.Maybe (listToMaybe, mapMaybe)
import System.Directory (getDirectoryContents)
import System.Environment
import System.IO.Error (tryIOError)
import System.Posix.Process
import System.Posix.IO
import System.Posix.Types (ProcessID)
import System.Posix.Types (Fd, ProcessID)
import System.Time
import Text.Printf
......@@ -79,6 +83,22 @@ connectConfig = ConnectConfig { recvTmo = 30
, sendTmo = 30
-- Returns the list of all open file descriptors of the current process.
listOpenFds :: (Error e) => ResultT e IO [Fd]
listOpenFds = liftM filterReadable
$ liftIO (getDirectoryContents "/proc/self/fd") `orElse`
liftIO (getDirectoryContents "/dev/fd") `orElse`
([] <$ logInfo "Listing open file descriptors isn't\
\ supported by the system,\
\ not cleaning them up!")
-- FIXME: If we can't get the list of file descriptors,
-- try to determine the maximum value and just return
-- the full range.
-- See
filterReadable :: (Read a) => [String] -> [a]
filterReadable = mapMaybe (fmap fst . listToMaybe . reads)
-- Code that is executed in a @fork@-ed process and that the replaces iteself
-- with the actual job process
runJobProcess :: JobId -> Client -> IO ()
......@@ -112,6 +132,10 @@ runJobProcess jid s = withErrorLogAt CRITICAL (show jid) $
closeFd clFdR
closeFd clFdW
fds <- (filter (> 2) . filter (/= fd)) <$> toErrorBase listOpenFds
logDebug $ "Closing every superfluous file descriptor: " ++ show fds
mapM_ (tryIOError . closeFd) fds
-- the master process will send the job id and the livelock file name
-- using the same protocol to the job process
-- we pass the job id as the first argument to the process;
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