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

   1 {-# LANGUAGE CPP #-}
   2
   3 module Distribution.Client.Signal
   4   ( installTerminationHandler
   5   , Terminated (..)
   6   )
   7 where
   8
   9 import qualified Control.Exception as Exception
  10
  11 #ifndef mingw32_HOST_OS
  12 import Control.Concurrent (myThreadId)
  13 import Control.Monad (void)
  14 import qualified System.Posix.Signals as Signals
  15 #endif
  16
  17 -- | Terminated is an asynchronous exception, thrown when
  18 -- SIGTERM is received. It's to 'kill' what 'UserInterrupt'
  19 -- is to Ctrl-C.
  20 data Terminated = Terminated
  21
  22 instance Exception.Exception Terminated where
  23   toException = Exception.asyncExceptionToException
  24   fromException = Exception.asyncExceptionFromException
  25
  26 instance Show Terminated where
  27   show Terminated = "terminated"
  28
  29 -- | Install a signal handler that initiates a controlled shutdown on receiving
  30 -- SIGTERM by throwing an asynchronous exception at the main thread. Must be
  31 -- called from the main thread.
  32 --
  33 -- It is a noop on Windows.
  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