cabal-install/src/Distribution/Client/Signal.hs

   1 {-# LANGUAGE CPP #-}
   2 module Distribution.Client.Signal
   3   ( installTerminationHandler
   4   , Terminated(..)
   5   )
   6 where
   7
   8 import qualified Control.Exception as Exception
   9
  10 #ifndef mingw32_HOST_OS
  11 import Control.Concurrent (myThreadId)
  12 import Control.Monad (void)
  13 import qualified System.Posix.Signals as Signals
  14 #endif
  15
  16 -- | Terminated is an asynchronous exception, thrown when
  17 -- SIGTERM is received. It's to 'kill' what 'UserInterrupt'
  18 -- is to Ctrl-C.
  19 data Terminated = Terminated
  20
  21 instance Exception.Exception Terminated where
  22   toException = Exception.asyncExceptionToException
  23   fromException = Exception.asyncExceptionFromException
  24
  25 instance Show Terminated where
  26   show Terminated = "terminated"
  27
  28 -- | Install a signal handler that initiates a controlled shutdown on receiving
  29 -- SIGTERM by throwing an asynchronous exception at the main thread. Must be
  30 -- called from the main thread.
  31 --
  32 -- It is a noop on Windows.
  33 --
  34 installTerminationHandler :: IO ()
  35
  36 #ifdef mingw32_HOST_OS
  37
  38 installTerminationHandler = return ()
  39
  40 #else
  41
  42 installTerminationHandler = do
  43   mainThreadId <- myThreadId
  44   void $ Signals.installHandler
  45     Signals.sigTERM
  46     (Signals.CatchOnce $ Exception.throwTo mainThreadId Terminated)
  47     Nothing
  48
  49 #endif