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|
{-# LANGUAGE Unsafe #-}
{-# LANGUAGE CPP
, NoImplicitPrelude
, ScopedTypeVariables
, BangPatterns
#-}
module GHC.Event.Control
(
-- * Managing the IO manager
Signal
, ControlMessage(..)
, Control
, newControl
, closeControl
-- ** Control message reception
, readControlMessage
-- *** File descriptors
, controlReadFd
, controlWriteFd
, wakeupReadFd
-- ** Control message sending
, sendWakeup
, sendDie
-- * Utilities
, setNonBlockingFD
) where
#include <ghcplatform.h>
#include "EventConfig.h"
import GHC.Base
import GHC.IORef
import GHC.Conc.Signal (Signal)
import GHC.Real (fromIntegral)
import GHC.Show (Show)
import GHC.Word (Word8)
import Foreign.C.Error (throwErrnoIfMinus1_, throwErrno, getErrno)
import Foreign.C.Types (CInt(..), CSize(..))
import Foreign.ForeignPtr (ForeignPtr, mallocForeignPtrBytes, withForeignPtr)
import Foreign.Marshal (alloca, allocaBytes)
import Foreign.Marshal.Array (allocaArray)
import Foreign.Ptr (castPtr)
import Foreign.Storable (peek, peekElemOff, poke)
import System.Posix.Internals (c_close, c_pipe, c_read, c_write,
setCloseOnExec, setNonBlockingFD)
import System.Posix.Types (Fd)
#if defined(HAVE_EVENTFD)
import Foreign.C.Error (throwErrnoIfMinus1, eBADF)
import Foreign.C.Types (CULLong(..))
#else
import Foreign.C.Error (eAGAIN, eWOULDBLOCK, eBADF)
#endif
data ControlMessage = CMsgWakeup
| CMsgDie
| CMsgSignal {-# UNPACK #-} !(ForeignPtr Word8)
{-# UNPACK #-} !Signal
deriving ( Eq -- ^ @since 4.4.0.0
, Show -- ^ @since 4.4.0.0
)
-- | The structure used to tell the IO manager thread what to do.
data Control = W {
controlReadFd :: {-# UNPACK #-} !Fd
, controlWriteFd :: {-# UNPACK #-} !Fd
#if defined(HAVE_EVENTFD)
, controlEventFd :: {-# UNPACK #-} !Fd
#else
, wakeupReadFd :: {-# UNPACK #-} !Fd
, wakeupWriteFd :: {-# UNPACK #-} !Fd
#endif
, didRegisterWakeupFd :: !Bool
-- | Have this Control's fds been cleaned up?
, controlIsDead :: !(IORef Bool)
}
#if defined(HAVE_EVENTFD)
wakeupReadFd :: Control -> Fd
wakeupReadFd = controlEventFd
{-# INLINE wakeupReadFd #-}
#endif
-- | Create the structure (usually a pipe) used for waking up the IO
-- manager thread from another thread.
newControl :: Bool -> IO Control
newControl shouldRegister = allocaArray 2 $ \fds -> do
let createPipe = do
throwErrnoIfMinus1_ "pipe" $ c_pipe fds
rd <- peekElemOff fds 0
wr <- peekElemOff fds 1
-- The write end must be non-blocking, since we may need to
-- poke the event manager from a signal handler.
setNonBlockingFD wr True
setCloseOnExec rd
setCloseOnExec wr
return (rd, wr)
(ctrl_rd, ctrl_wr) <- createPipe
#if defined(HAVE_EVENTFD)
ev <- throwErrnoIfMinus1 "eventfd" $ c_eventfd 0 0
setNonBlockingFD ev True
setCloseOnExec ev
when shouldRegister $ c_setIOManagerWakeupFd ev
#else
(wake_rd, wake_wr) <- createPipe
when shouldRegister $ c_setIOManagerWakeupFd wake_wr
#endif
isDead <- newIORef False
return W { controlReadFd = fromIntegral ctrl_rd
, controlWriteFd = fromIntegral ctrl_wr
#if defined(HAVE_EVENTFD)
, controlEventFd = fromIntegral ev
#else
, wakeupReadFd = fromIntegral wake_rd
, wakeupWriteFd = fromIntegral wake_wr
#endif
, didRegisterWakeupFd = shouldRegister
, controlIsDead = isDead
}
-- | Close the control structure used by the IO manager thread.
-- N.B. If this Control is the Control whose wakeup file was registered with
-- the RTS, then *BEFORE* the wakeup file is closed, we must call
-- c_setIOManagerWakeupFd (-1), so that the RTS does not try to use the wakeup
-- file after it has been closed.
--
-- Note, however, that even if we do the above, this function is still racy
-- since we do not synchronize between here and ioManagerWakeup.
-- ioManagerWakeup ignores failures that arise from this case.
closeControl :: Control -> IO ()
closeControl w = do
_ <- atomicSwapIORef (controlIsDead w) True
_ <- c_close . fromIntegral . controlReadFd $ w
_ <- c_close . fromIntegral . controlWriteFd $ w
when (didRegisterWakeupFd w) $ c_setIOManagerWakeupFd (-1)
#if defined(HAVE_EVENTFD)
_ <- c_close . fromIntegral . controlEventFd $ w
#else
_ <- c_close . fromIntegral . wakeupReadFd $ w
_ <- c_close . fromIntegral . wakeupWriteFd $ w
#endif
return ()
io_MANAGER_WAKEUP, io_MANAGER_DIE :: Word8
io_MANAGER_WAKEUP = 0xff
io_MANAGER_DIE = 0xfe
#if !defined(HAVE_SIGNAL_H)
readControlMessage :: Control -> Fd -> IO ControlMessage
readControlMessage _ _ = errorWithoutStackTrace "readControlMessage"
#else
foreign import ccall "__hscore_sizeof_siginfo_t"
sizeof_siginfo_t :: CSize
readControlMessage :: Control -> Fd -> IO ControlMessage
readControlMessage ctrl fd
| fd == wakeupReadFd ctrl = allocaBytes wakeupBufferSize $ \p -> do
throwErrnoIfMinus1_ "readWakeupMessage" $
c_read (fromIntegral fd) p (fromIntegral wakeupBufferSize)
return CMsgWakeup
| otherwise =
alloca $ \p -> do
throwErrnoIfMinus1_ "readControlMessage" $
c_read (fromIntegral fd) p 1
s <- peek p
case s of
-- Wakeup messages shouldn't be sent on the control
-- file descriptor but we handle them anyway.
_ | s == io_MANAGER_WAKEUP -> return CMsgWakeup
_ | s == io_MANAGER_DIE -> return CMsgDie
_ -> do -- Signal
fp <- mallocForeignPtrBytes (fromIntegral sizeof_siginfo_t)
withForeignPtr fp $ \p_siginfo -> do
r <- c_read (fromIntegral fd) (castPtr p_siginfo)
sizeof_siginfo_t
when (r /= fromIntegral sizeof_siginfo_t) $
errorWithoutStackTrace "failed to read siginfo_t"
let !s' = fromIntegral s
return $ CMsgSignal fp s'
where wakeupBufferSize =
#if defined(HAVE_EVENTFD)
8
#else
4096
#endif
#endif
sendWakeup :: Control -> IO ()
#if defined(HAVE_EVENTFD)
sendWakeup c = do
n <- c_eventfd_write (fromIntegral (controlEventFd c)) 1
case n of
0 -> return ()
_ -> do errno <- getErrno
-- Check that Control is still alive if we failed, since it's
-- possible that someone cleaned up the fds behind our backs and
-- consequently eventfd_write failed with EBADF. If it is dead
-- then just swallow the error since we are shutting down
-- anyways. Otherwise we will see failures during shutdown from
-- setnumcapabilities001 (#12038)
isDead <- readIORef (controlIsDead c)
if isDead && errno == eBADF
then return ()
else throwErrno "sendWakeup"
#else
sendWakeup c = do
n <- sendMessage (wakeupWriteFd c) CMsgWakeup
case n of
_ | n /= -1 -> return ()
| otherwise -> do
errno <- getErrno
isDead <- readIORef (controlIsDead c)
case () of
_ -- Someone else has beat us to waking it up
| errno == eAGAIN -> return ()
| errno == eWOULDBLOCK -> return ()
-- we are shutting down
| errno == eBADF && isDead -> return ()
-- something bad happened
| otherwise -> throwErrno "sendWakeup"
#endif
sendDie :: Control -> IO ()
sendDie c = throwErrnoIfMinus1_ "sendDie" $
sendMessage (controlWriteFd c) CMsgDie
sendMessage :: Fd -> ControlMessage -> IO Int
sendMessage fd msg = alloca $ \p -> do
case msg of
CMsgWakeup -> poke p io_MANAGER_WAKEUP
CMsgDie -> poke p io_MANAGER_DIE
CMsgSignal _fp _s -> errorWithoutStackTrace "Signals can only be sent from within the RTS"
fromIntegral `fmap` c_write (fromIntegral fd) p 1
#if defined(HAVE_EVENTFD)
foreign import ccall unsafe "sys/eventfd.h eventfd"
c_eventfd :: CInt -> CInt -> IO CInt
foreign import ccall unsafe "sys/eventfd.h eventfd_write"
c_eventfd_write :: CInt -> CULLong -> IO CInt
#endif
#if defined(wasm32_HOST_ARCH)
c_setIOManagerWakeupFd :: CInt -> IO ()
c_setIOManagerWakeupFd _ = pure ()
#else
foreign import ccall unsafe "setIOManagerWakeupFd"
c_setIOManagerWakeupFd :: CInt -> IO ()
#endif
|
