dist-install/build/GHC/IO/Handle/Lock/LinuxOFD.hs

    {-# OPTIONS_GHC -optc-D_FILE_OFFSET_BITS=64 #-}
    {-# LINE 1 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
    {-# LANGUAGE CPP #-}
    {-# LANGUAGE InterruptibleFFI #-}
    {-# LANGUAGE MultiWayIf #-}
    {-# LANGUAGE NoImplicitPrelude #-}

    -- | File locking via the Linux open-fd locking mechanism.
    module GHC.IO.Handle.Lock.LinuxOFD where

    {-# LINE 14 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}

    -- Not only is this a good idea but it also works around #17950.

    import Data.Function
    import Data.Functor
    import Foreign.C.Error
    import Foreign.C.Types
    import Foreign.Marshal.Utils
    import Foreign.Storable
    import GHC.Base
    import GHC.IO.Exception
    import GHC.IO.FD
    import GHC.IO.Handle.FD
    import GHC.IO.Handle.Lock.Common
    import GHC.IO.Handle.Types (Handle)
    import GHC.Ptr
    import System.Posix.Types (COff, CPid)

    -- Linux open file descriptor locking.
    --
    -- We prefer this over BSD locking (e.g. flock) since the latter appears to
    -- break in some NFS configurations. Note that we intentionally do not try to
    -- use ordinary POSIX file locking due to its peculiar semantics under
    -- multi-threaded environments.

    foreign import ccall interruptible "fcntl"
      c_fcntl :: CInt -> CInt -> Ptr FLock -> IO CInt

    data FLock  = FLock { l_type   :: CShort
                        , l_whence :: CShort
                        , l_start  :: COff
                        , l_len    :: COff
                        , l_pid    :: CPid
                        }

    instance Storable FLock where
        sizeOf _ = (32)
    {-# LINE 55 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
        alignment _ = 8
    {-# LINE 56 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
        poke ptr x = do
            fillBytes ptr 0 (sizeOf x)
            (\hsc_ptr -> pokeByteOff hsc_ptr 0)   ptr (l_type x)
    {-# LINE 59 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
            (\hsc_ptr -> pokeByteOff hsc_ptr 2) ptr (l_whence x)
    {-# LINE 60 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
            (\hsc_ptr -> pokeByteOff hsc_ptr 8)  ptr (l_start x)
    {-# LINE 61 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
            (\hsc_ptr -> pokeByteOff hsc_ptr 16)    ptr (l_len x)
    {-# LINE 62 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
            (\hsc_ptr -> pokeByteOff hsc_ptr 24)    ptr (l_pid x)
    {-# LINE 63 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
        peek ptr = do
            FLock <$> (\hsc_ptr -> peekByteOff hsc_ptr 0)   ptr
    {-# LINE 65 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                  <*> (\hsc_ptr -> peekByteOff hsc_ptr 2) ptr
    {-# LINE 66 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                  <*> (\hsc_ptr -> peekByteOff hsc_ptr 8)  ptr
    {-# LINE 67 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                  <*> (\hsc_ptr -> peekByteOff hsc_ptr 16)    ptr
    {-# LINE 68 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                  <*> (\hsc_ptr -> peekByteOff hsc_ptr 24)    ptr
    {-# LINE 69 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}

    lockImpl :: Handle -> String -> LockMode -> Bool -> IO Bool
    lockImpl h ctx mode block = do
      FD{fdFD = fd} <- handleToFd h
      with flock $ \flock_ptr -> fix $ \retry -> do
          ret <- c_fcntl fd mode' flock_ptr
          case ret of
            0 -> return True
            _ -> getErrno >>= \errno -> if
              | not block && errno == eWOULDBLOCK -> return False
              | errno == eINTR -> retry
              | otherwise -> ioException $ errnoToIOError ctx errno (Just h) Nothing
      where
        flock = FLock { l_type = case mode of
                                   SharedLock -> 0
    {-# LINE 84 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                                   ExclusiveLock -> 1
    {-# LINE 85 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                      , l_whence = 0
    {-# LINE 86 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                      , l_start = 0
                      , l_len = 0
                      , l_pid = 0
                      }
        mode'
          | block     = 38
    {-# LINE 92 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
          | otherwise = 37
    {-# LINE 93 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}

    unlockImpl :: Handle -> IO ()
    unlockImpl h = do
      FD{fdFD = fd} <- handleToFd h
      let flock = FLock { l_type = 2
    {-# LINE 98 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                        , l_whence = 0
    {-# LINE 99 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}
                        , l_start = 0
                        , l_len = 0
                        , l_pid = 0
                        }
      throwErrnoIfMinus1_ "hUnlock"
          $ with flock $ c_fcntl fd 37
    {-# LINE 105 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}

    {-# LINE 107 "libraries/base/GHC/IO/Handle/Lock/LinuxOFD.hsc" #-}