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{- Running a long or expensive batch operation niced.
-
- Copyright 2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE CPP #-}
module Utility.Batch where
import Common
#ifndef mingw32_HOST_OS
import qualified Build.SysConfig
#endif
#if defined(linux_HOST_OS) || defined(__ANDROID__)
import Control.Concurrent.Async
import System.Posix.Process
#endif
import qualified Control.Exception as E
import System.Process (env)
{- Runs an operation, at batch priority.
-
- This is done by running it in a bound thread, which on Linux can be set
- to have a different nice level than the rest of the program. Note that
- due to running in a bound thread, some operations may be more expensive
- to perform. Also note that if the action calls forkIO or forkOS itself,
- that will make a new thread that does not have the batch priority.
-
- POSIX threads do not support separate nice levels, so on other operating
- systems, the action is simply ran.
-}
batch :: IO a -> IO a
#if defined(linux_HOST_OS) || defined(__ANDROID__)
batch a = wait =<< batchthread
where
batchthread = asyncBound $ do
setProcessPriority 0 maxNice
a
#else
batch a = a
#endif
maxNice :: Int
maxNice = 19
{- Converts a command to run niced. -}
toBatchCommand :: (String, [CommandParam]) -> (String, [CommandParam])
toBatchCommand (command, params) = (command', params')
where
#ifndef mingw32_HOST_OS
commandline = unwords $ map shellEscape $ command : toCommand params
nicedcommand
| Build.SysConfig.nice = "nice " ++ commandline
| otherwise = commandline
command' = "sh"
params' =
[ Param "-c"
, Param $ "exec " ++ nicedcommand
]
#else
command' = command
params' = params
#endif
{- Runs a command in a way that's suitable for batch jobs that can be
- interrupted.
-
- The command is run niced. If the calling thread receives an async
- exception, it sends the command a SIGTERM, and after the command
- finishes shuttting down, it re-raises the async exception. -}
batchCommand :: String -> [CommandParam] -> IO Bool
batchCommand command params = batchCommandEnv command params Nothing
batchCommandEnv :: String -> [CommandParam] -> Maybe [(String, String)] -> IO Bool
batchCommandEnv command params environ = do
(_, _, _, pid) <- createProcess $ p { env = environ }
r <- E.try (waitForProcess pid) :: IO (Either E.SomeException ExitCode)
case r of
Right ExitSuccess -> return True
Right _ -> return False
Left asyncexception -> do
terminateProcess pid
void $ waitForProcess pid
E.throwIO asyncexception
where
(command', params') = toBatchCommand (command, params)
p = proc command' $ toCommand params'
|
