Sync.lhs 32.1 KB
 Simon Marlow committed Aug 10, 2010 1 \begin{code}  dterei committed Oct 25, 2011 2 {-# LANGUAGE Unsafe #-}  3 4 5 6 7 8 9 {-# LANGUAGE CPP , NoImplicitPrelude , BangPatterns , MagicHash , UnboxedTuples , UnliftedFFITypes , DeriveDataTypeable  Ian Lynagh committed Apr 24, 2011 10  , StandaloneDeriving  Simon Marlow committed Mar 29, 2011 11  , RankNTypes  12  #-}  Simon Marlow committed Aug 10, 2010 13 14 {-# OPTIONS_GHC -fno-warn-missing-signatures #-} {-# OPTIONS_HADDOCK not-home #-}  15   Simon Marlow committed Aug 10, 2010 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 ----------------------------------------------------------------------------- -- | -- Module : GHC.Conc.Sync -- Copyright : (c) The University of Glasgow, 1994-2002 -- License : see libraries/base/LICENSE -- -- Maintainer : cvs-ghc@haskell.org -- Stability : internal -- Portability : non-portable (GHC extensions) -- -- Basic concurrency stuff. -- ----------------------------------------------------------------------------- -- No: #hide, because bits of this module are exposed by the stm package. -- However, we don't want this module to be the home location for the -- bits it exports, we'd rather have Control.Concurrent and the other -- higher level modules be the home. Hence: -- #not-home module GHC.Conc.Sync ( ThreadId(..) -- * Forking and suchlike  ian@well-typed.com committed Oct 27, 2012 40  , forkIO  Simon Marlow committed Mar 29, 2011 41  , forkIOWithUnmask  ian@well-typed.com committed Oct 27, 2012 42  , forkOn  Simon Marlow committed Mar 30, 2011 43  , forkOnWithUnmask  ian@well-typed.com committed Oct 27, 2012 44 45 46 47 48 49 50 51 52 53 54  , numCapabilities , getNumCapabilities , setNumCapabilities , getNumProcessors , numSparks , childHandler , myThreadId , killThread , throwTo , par , pseq  Simon Marlow committed Aug 10, 2010 55  , runSparks  ian@well-typed.com committed Oct 27, 2012 56 57 58  , yield , labelThread , mkWeakThreadId  Simon Marlow committed Aug 10, 2010 59 60  , ThreadStatus(..), BlockReason(..)  ian@well-typed.com committed Oct 27, 2012 61  , threadStatus  Simon Marlow committed Mar 01, 2011 62  , threadCapability  Simon Marlow committed Aug 10, 2010 63   Simon Marlow committed May 02, 2014 64 65 66 67 68 69  -- * Allocation counter and quota , setAllocationCounter , getAllocationCounter , enableAllocationLimit , disableAllocationLimit  Simon Marlow committed Aug 10, 2010 70 71  -- * TVars , STM(..)  ian@well-typed.com committed Oct 27, 2012 72 73 74 75 76 77 78  , atomically , retry , orElse , throwSTM , catchSTM , alwaysSucceeds , always  Simon Marlow committed Aug 10, 2010 79  , TVar(..)  ian@well-typed.com committed Oct 27, 2012 80 81 82 83 84 85  , newTVar , newTVarIO , readTVar , readTVarIO , writeTVar , unsafeIOToSTM  Simon Marlow committed Aug 10, 2010 86 87 88 89 90  -- * Miscellaneous , withMVar , modifyMVar_  ian@well-typed.com committed Oct 27, 2012 91 92  , setUncaughtExceptionHandler , getUncaughtExceptionHandler  Simon Marlow committed Aug 10, 2010 93 94 95 96 97 98  , reportError, reportStackOverflow , sharedCAF ) where  ian@well-typed.com committed Feb 16, 2013 99 import Foreign  Simon Marlow committed Aug 10, 2010 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 import Foreign.C #ifdef mingw32_HOST_OS import Data.Typeable #endif #ifndef mingw32_HOST_OS import Data.Dynamic #endif import Control.Monad import Data.Maybe import GHC.Base import {-# SOURCE #-} GHC.IO.Handle ( hFlush ) import {-# SOURCE #-} GHC.IO.Handle.FD ( stdout ) import GHC.IO  ian@well-typed.com committed Oct 25, 2012 116 import GHC.IO.Encoding.UTF8  Simon Marlow committed Aug 10, 2010 117 118 import GHC.IO.Exception import GHC.Exception  ian@well-typed.com committed Oct 25, 2012 119 import qualified GHC.Foreign  Simon Marlow committed Aug 10, 2010 120 121 import GHC.IORef import GHC.MVar  ian@well-typed.com committed Oct 25, 2012 122 import GHC.Ptr  Simon Marlow committed Aug 10, 2010 123 124 import GHC.Real ( fromIntegral ) import GHC.Show ( Show(..), showString )  Simon Marlow committed Apr 12, 2012 125 import GHC.Weak  Simon Marlow committed Aug 10, 2010 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185  infixr 0 par, pseq \end{code} %************************************************************************ %* * \subsection{@ThreadId@, @par@, and @fork@} %* * %************************************************************************ \begin{code} data ThreadId = ThreadId ThreadId# deriving( Typeable ) -- ToDo: data ThreadId = ThreadId (Weak ThreadId#) -- But since ThreadId# is unlifted, the Weak type must use open -- type variables. {- ^ A 'ThreadId' is an abstract type representing a handle to a thread. 'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where the 'Ord' instance implements an arbitrary total ordering over 'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued 'ThreadId' to string form; showing a 'ThreadId' value is occasionally useful when debugging or diagnosing the behaviour of a concurrent program. /Note/: in GHC, if you have a 'ThreadId', you essentially have a pointer to the thread itself. This means the thread itself can\'t be garbage collected until you drop the 'ThreadId'. This misfeature will hopefully be corrected at a later date. -} instance Show ThreadId where showsPrec d t = showString "ThreadId " . showsPrec d (getThreadId (id2TSO t)) foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> CInt id2TSO :: ThreadId -> ThreadId# id2TSO (ThreadId t) = t foreign import ccall unsafe "cmp_thread" cmp_thread :: ThreadId# -> ThreadId# -> CInt -- Returns -1, 0, 1 cmpThread :: ThreadId -> ThreadId -> Ordering cmpThread t1 t2 = case cmp_thread (id2TSO t1) (id2TSO t2) of -1 -> LT 0 -> EQ _ -> GT -- must be 1 instance Eq ThreadId where t1 == t2 = case t1 cmpThread t2 of EQ -> True _ -> False instance Ord ThreadId where compare = cmpThread  Simon Marlow committed May 02, 2014 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 -- | Every thread has an allocation counter that tracks how much -- memory has been allocated by the thread. The counter is -- initialized to zero, and 'setAllocationCounter' sets the current -- value. The allocation counter counts *down*, so in the absence of -- a call to 'setAllocationCounter' its value is the negation of the -- number of bytes of memory allocated by the thread. -- -- There are two things that you can do with this counter: -- -- * Use it as a simple profiling mechanism, with -- 'getAllocationCounter'. -- -- * Use it as a resource limit. See 'enableAllocationLimit'. -- -- Allocation accounting is accurate only to about 4Kbytes. -- setAllocationCounter :: Int64 -> IO () setAllocationCounter i = do ThreadId t <- myThreadId rts_setThreadAllocationCounter t i -- | Return the current value of the allocation counter for the -- current thread. getAllocationCounter :: IO Int64 getAllocationCounter = do ThreadId t <- myThreadId rts_getThreadAllocationCounter t -- | Enables the allocation counter to be treated as a limit for the -- current thread. When the allocation limit is enabled, if the -- allocation counter counts down below zero, the thread will be sent -- the 'AllocationLimitExceeded' asynchronous exception. When this -- happens, the counter is reinitialised (by default -- to 100K, but tunable with the @+RTS -xq@ option) so that it can handle -- the exception and perform any necessary clean up. If it exhausts -- this additional allowance, another 'AllocationLimitExceeded' exception -- is sent, and so forth. -- -- Note that memory allocation is unrelated to /live memory/, also -- known as /heap residency/. A thread can allocate a large amount of -- memory and retain anything between none and all of it. It is -- better to think of the allocation limit as a limit on -- /CPU time/, rather than a limit on memory. -- -- Compared to using timeouts, allocation limits don't count time -- spent blocked or in foreign calls. -- enableAllocationLimit :: IO () enableAllocationLimit = do ThreadId t <- myThreadId rts_enableThreadAllocationLimit t -- | Disable allocation limit processing for the current thread. disableAllocationLimit :: IO () disableAllocationLimit = do ThreadId t <- myThreadId rts_disableThreadAllocationLimit t -- We cannot do these operations safely on another thread, because on -- a 32-bit machine we cannot do atomic operations on a 64-bit value. -- Therefore, we only expose APIs that allow getting and setting the -- limit of the current thread. foreign import ccall unsafe "rts_setThreadAllocationCounter" rts_setThreadAllocationCounter :: ThreadId# -> Int64 -> IO () foreign import ccall unsafe "rts_getThreadAllocationCounter" rts_getThreadAllocationCounter :: ThreadId# -> IO Int64 foreign import ccall unsafe "rts_enableThreadAllocationLimit" rts_enableThreadAllocationLimit :: ThreadId# -> IO () foreign import ccall unsafe "rts_disableThreadAllocationLimit" rts_disableThreadAllocationLimit :: ThreadId# -> IO ()  Simon Marlow committed Aug 10, 2010 260 {- |  Simon Marlow committed May 02, 2014 261 Creates a new thread to run the 'IO' computation passed as the  Simon Marlow committed Aug 10, 2010 262 263 264 first argument, and returns the 'ThreadId' of the newly created thread.  Simon Marlow committed May 02, 2014 265 266 267 268 The new thread will be a lightweight, /unbound/ thread. Foreign calls made by this thread are not guaranteed to be made by any particular OS thread; if you need foreign calls to be made by a particular OS thread, then use 'Control.Concurrent.forkOS' instead.  Simon Marlow committed Aug 10, 2010 269   Simon Marlow committed May 02, 2014 270 271 The new thread inherits the /masked/ state of the parent (see 'Control.Exception.mask').  Simon Marlow committed Aug 10, 2010 272 273 274 275  The newly created thread has an exception handler that discards the exceptions 'BlockedIndefinitelyOnMVar', 'BlockedIndefinitelyOnSTM', and 'ThreadKilled', and passes all other exceptions to the uncaught  Edward Z. Yang committed Jul 26, 2011 276 exception handler.  Simon Marlow committed Aug 10, 2010 277 278 279 280 281 282 283 -} forkIO :: IO () -> IO ThreadId forkIO action = IO $\ s -> case (fork# action_plus s) of (# s1, tid #) -> (# s1, ThreadId tid #) where action_plus = catchException action childHandler  Simon Marlow committed Mar 29, 2011 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 -- | Like 'forkIO', but the child thread is passed a function that can -- be used to unmask asynchronous exceptions. This function is -- typically used in the following way -- -- > ... mask_$ forkIOWithUnmask $\unmask -> -- > catch (unmask ...) handler -- -- so that the exception handler in the child thread is established -- with asynchronous exceptions masked, meanwhile the main body of -- the child thread is executed in the unmasked state. -- -- Note that the unmask function passed to the child thread should -- only be used in that thread; the behaviour is undefined if it is -- invoked in a different thread. --  Herbert Valerio Riedel committed Sep 22, 2013 299 -- /Since: 4.4.0.0/  Simon Marlow committed Mar 29, 2011 300 301 302 forkIOWithUnmask :: ((forall a . IO a -> IO a) -> IO ()) -> IO ThreadId forkIOWithUnmask io = forkIO (io unsafeUnmask)  Simon Marlow committed Aug 10, 2010 303 {- |  Simon Marlow committed Mar 30, 2011 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 Like 'forkIO', but lets you specify on which processor the thread should run. Unlike a forkIO thread, a thread created by forkOn will stay on the same processor for its entire lifetime (forkIO threads can migrate between processors according to the scheduling policy). forkOn is useful for overriding the scheduling policy when you know in advance how best to distribute the threads. The Int argument specifies a /capability number/ (see 'getNumCapabilities'). Typically capabilities correspond to physical processors, but the exact behaviour is implementation-dependent. The value passed to 'forkOn' is interpreted modulo the total number of capabilities as returned by 'getNumCapabilities'. GHC note: the number of capabilities is specified by the @+RTS -N@ option when the program is started. Capabilities can be fixed to actual processor cores with @+RTS -qa@ if the underlying operating system supports that, although in practice this is usually unnecessary  ian@well-typed.com committed Sep 13, 2012 321 (and may actually degrade performance in some cases - experimentation  Simon Marlow committed Mar 30, 2011 322 is recommended).  Herbert Valerio Riedel committed Sep 22, 2013 323 324  /Since: 4.4.0.0/  Simon Marlow committed Aug 10, 2010 325 -}  Simon Marlow committed Mar 30, 2011 326 327 forkOn :: Int -> IO () -> IO ThreadId forkOn (I# cpu) action = IO$ \ s ->  Simon Marlow committed Aug 10, 2010 328 329 330 331  case (forkOn# cpu action_plus s) of (# s1, tid #) -> (# s1, ThreadId tid #) where action_plus = catchException action childHandler  Simon Marlow committed Mar 29, 2011 332 -- | Like 'forkIOWithUnmask', but the child thread is pinned to the  Simon Marlow committed Mar 30, 2011 333 -- given CPU, as with 'forkOn'.  Herbert Valerio Riedel committed Sep 22, 2013 334 335 -- -- /Since: 4.4.0.0/  Simon Marlow committed Mar 30, 2011 336 337 forkOnWithUnmask :: Int -> ((forall a . IO a -> IO a) -> IO ()) -> IO ThreadId forkOnWithUnmask cpu io = forkOn cpu (io unsafeUnmask)  Simon Marlow committed Mar 29, 2011 338   Simon Marlow committed Aug 10, 2010 339 340 -- | the value passed to the @+RTS -N@ flag. This is the number of -- Haskell threads that can run truly simultaneously at any given  Simon Marlow committed Mar 30, 2011 341 -- time, and is typically set to the number of physical processor cores on  Simon Marlow committed Aug 10, 2010 342 -- the machine.  daniel.is.fischer committed Oct 04, 2011 343 --  Simon Marlow committed Dec 22, 2010 344 345 346 -- Strictly speaking it is better to use 'getNumCapabilities', because -- the number of capabilities might vary at runtime. --  Simon Marlow committed Aug 10, 2010 347 numCapabilities :: Int  Simon Marlow committed Dec 22, 2010 348 349 350 351 numCapabilities = unsafePerformIO $getNumCapabilities {- | Returns the number of Haskell threads that can run truly  Simon Marlow committed Dec 19, 2011 352 353 simultaneously (on separate physical processors) at any given time. To change this value, use 'setNumCapabilities'.  Herbert Valerio Riedel committed Sep 22, 2013 354 355  /Since: 4.4.0.0/  Simon Marlow committed Dec 22, 2010 356 357 358 -} getNumCapabilities :: IO Int getNumCapabilities = do  Simon Marlow committed Dec 11, 2012 359  n <- peek enabled_capabilities  Simon Marlow committed Dec 22, 2010 360  return (fromIntegral n)  Simon Marlow committed Aug 10, 2010 361   Simon Marlow committed Dec 06, 2011 362 363 {- | Set the number of Haskell threads that can run truly simultaneously  Simon Marlow committed Dec 19, 2011 364 365 366 367 368 369 370 371 372 (on separate physical processors) at any given time. The number passed to forkOn is interpreted modulo this value. The initial value is given by the @+RTS -N@ runtime flag. This is also the number of threads that will participate in parallel garbage collection. It is strongly recommended that the number of capabilities is not set larger than the number of physical processor cores, and it may often be beneficial to leave one or more cores free to avoid contention with other processes in the machine.  Herbert Valerio Riedel committed Sep 22, 2013 373 374  /Since: 4.5.0.0/  Simon Marlow committed Dec 06, 2011 375 376 377 378 379 380 381 -} setNumCapabilities :: Int -> IO () setNumCapabilities i = c_setNumCapabilities (fromIntegral i) foreign import ccall safe "setNumCapabilities" c_setNumCapabilities :: CUInt -> IO ()  Herbert Valerio Riedel committed Sep 22, 2013 382 383 384 -- | Returns the number of CPUs that the machine has -- -- /Since: 4.5.0.0/  Simon Marlow committed Dec 07, 2011 385 386 387 388 389 390 getNumProcessors :: IO Int getNumProcessors = fmap fromIntegral c_getNumberOfProcessors foreign import ccall unsafe "getNumberOfProcessors" c_getNumberOfProcessors :: IO CUInt  Simon Marlow committed Aug 10, 2010 391 392 393 394 -- | Returns the number of sparks currently in the local spark pool numSparks :: IO Int numSparks = IO$ \s -> case numSparks# s of (# s', n #) -> (# s', I# n #)  Simon Marlow committed Dec 11, 2012 395 foreign import ccall "&enabled_capabilities" enabled_capabilities :: Ptr CInt  pcapriotti committed Apr 24, 2012 396   Simon Marlow committed Aug 10, 2010 397 398 399 400 childHandler :: SomeException -> IO () childHandler err = catchException (real_handler err) childHandler real_handler :: SomeException -> IO ()  Simon Marlow committed Dec 10, 2012 401 402 403 404 405 406 real_handler se | Just BlockedIndefinitelyOnMVar <- fromException se = return () | Just BlockedIndefinitelyOnSTM <- fromException se = return () | Just ThreadKilled <- fromException se = return () | Just StackOverflow <- fromException se = reportStackOverflow | otherwise = reportError se  Simon Marlow committed Aug 10, 2010 407 408 409 410 411 412 413 414 415 416 417 418  {- | 'killThread' raises the 'ThreadKilled' exception in the given thread (GHC only). > killThread tid = throwTo tid ThreadKilled -} killThread :: ThreadId -> IO () killThread tid = throwTo tid ThreadKilled {- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).  thoughtpolice committed Oct 11, 2013 419 Exception delivery synchronizes between the source and target thread:  Simon Marlow committed Aug 10, 2010 420 'throwTo' does not return until the exception has been raised in the  thoughtpolice committed Oct 11, 2013 421 422 423 424 target thread. The calling thread can thus be certain that the target thread has received the exception. Exception delivery is also atomic with respect to other exceptions. Atomicity is a useful property to have when dealing with race conditions: e.g. if there are two threads that  Simon Marlow committed Aug 10, 2010 425 426 427 428 429 430 431 432 433 434 can kill each other, it is guaranteed that only one of the threads will get to kill the other. Whatever work the target thread was doing when the exception was raised is not lost: the computation is suspended until required by another thread. If the target thread is currently making a foreign call, then the exception will not be raised (and hence 'throwTo' will not return) until the call has completed. This is the case regardless of whether  Simon Marlow committed Oct 14, 2010 435 436 437 438 the call is inside a 'mask' or not. However, in GHC a foreign call can be annotated as @interruptible@, in which case a 'throwTo' will cause the RTS to attempt to cause the call to return; see the GHC documentation for more details.  Simon Marlow committed Aug 10, 2010 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456  Important note: the behaviour of 'throwTo' differs from that described in the paper \"Asynchronous exceptions in Haskell\" (). In the paper, 'throwTo' is non-blocking; but the library implementation adopts a more synchronous design in which 'throwTo' does not return until the exception is received by the target thread. The trade-off is discussed in Section 9 of the paper. Like any blocking operation, 'throwTo' is therefore interruptible (see Section 5.3 of the paper). Unlike other interruptible operations, however, 'throwTo' is /always/ interruptible, even if it does not actually block. There is no guarantee that the exception will be delivered promptly, although the runtime will endeavour to ensure that arbitrary delays don't occur. In GHC, an exception can only be raised when a thread reaches a /safe point/, where a safe point is where memory allocation occurs. Some loops do not perform any memory allocation inside the loop and therefore cannot be interrupted by a 'throwTo'.  Simon Marlow committed May 24, 2011 457 458 459 460 461 462 463 464 465 466 467 If the target of 'throwTo' is the calling thread, then the behaviour is the same as 'Control.Exception.throwIO', except that the exception is thrown as an asynchronous exception. This means that if there is an enclosing pure computation, which would be the case if the current IO operation is inside 'unsafePerformIO' or 'unsafeInterleaveIO', that computation is not permanently replaced by the exception, but is suspended as if it had received an asynchronous exception. Note that if 'throwTo' is called with the current thread as the target, the exception will be thrown even if the thread is currently inside 'mask' or 'uninterruptibleMask'.  Simon Marlow committed Aug 10, 2010 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497  -} throwTo :: Exception e => ThreadId -> e -> IO () throwTo (ThreadId tid) ex = IO $\ s -> case (killThread# tid (toException ex) s) of s1 -> (# s1, () #) -- | Returns the 'ThreadId' of the calling thread (GHC only). myThreadId :: IO ThreadId myThreadId = IO$ \s -> case (myThreadId# s) of (# s1, tid #) -> (# s1, ThreadId tid #) -- |The 'yield' action allows (forces, in a co-operative multitasking -- implementation) a context-switch to any other currently runnable -- threads (if any), and is occasionally useful when implementing -- concurrency abstractions. yield :: IO () yield = IO $\s -> case (yield# s) of s1 -> (# s1, () #) {- | 'labelThread' stores a string as identifier for this thread if you built a RTS with debugging support. This identifier will be used in the debugging output to make distinction of different threads easier (otherwise you only have the thread state object\'s address in the heap). Other applications like the graphical Concurrent Haskell Debugger () may choose to overload 'labelThread' for their purposes as well. -} labelThread :: ThreadId -> String -> IO ()  ian@well-typed.com committed Oct 25, 2012 498 499 500 501 labelThread (ThreadId t) str = GHC.Foreign.withCString utf8 str$ \(Ptr p) -> IO $\ s -> case labelThread# t p s of s1 -> (# s1, () #)  Simon Marlow committed Aug 10, 2010 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526  -- Nota Bene: 'pseq' used to be 'seq' -- but 'seq' is now defined in PrelGHC -- -- "pseq" is defined a bit weirdly (see below) -- -- The reason for the strange "lazy" call is that -- it fools the compiler into thinking that pseq and par are non-strict in -- their second argument (even if it inlines pseq at the call site). -- If it thinks pseq is strict in "y", then it often evaluates -- "y" before "x", which is totally wrong. {-# INLINE pseq #-} pseq :: a -> b -> b pseq x y = x seq lazy y {-# INLINE par #-} par :: a -> b -> b par x y = case (par# x) of { _ -> lazy y } -- | Internal function used by the RTS to run sparks. runSparks :: IO () runSparks = IO loop where loop s = case getSpark# s of (# s', n, p #) ->  Jan Stolarek committed Sep 18, 2013 527 528 529  if isTrue# (n ==# 0#) then (# s', () #) else p seq loop s'  Simon Marlow committed Aug 10, 2010 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562  data BlockReason = BlockedOnMVar -- ^blocked on on 'MVar' | BlockedOnBlackHole -- ^blocked on a computation in progress by another thread | BlockedOnException -- ^blocked in 'throwTo' | BlockedOnSTM -- ^blocked in 'retry' in an STM transaction | BlockedOnForeignCall -- ^currently in a foreign call | BlockedOnOther -- ^blocked on some other resource. Without @-threaded@, -- I\/O and 'threadDelay' show up as 'BlockedOnOther', with @-threaded@ -- they show up as 'BlockedOnMVar'. deriving (Eq,Ord,Show) -- | The current status of a thread data ThreadStatus = ThreadRunning -- ^the thread is currently runnable or running | ThreadFinished -- ^the thread has finished | ThreadBlocked BlockReason -- ^the thread is blocked on some resource | ThreadDied -- ^the thread received an uncaught exception deriving (Eq,Ord,Show) threadStatus :: ThreadId -> IO ThreadStatus threadStatus (ThreadId t) = IO$ \s -> case threadStatus# t s of  Simon Marlow committed Mar 01, 2011 563  (# s', stat, _cap, _locked #) -> (# s', mk_stat (I# stat) #)  Simon Marlow committed Aug 10, 2010 564 565 566 567  where -- NB. keep these in sync with includes/Constants.h mk_stat 0 = ThreadRunning mk_stat 1 = ThreadBlocked BlockedOnMVar  Edward Z. Yang committed Jul 09, 2013 568 569 570  mk_stat 2 = ThreadBlocked BlockedOnMVar -- XXX distinguish? mk_stat 3 = ThreadBlocked BlockedOnBlackHole mk_stat 7 = ThreadBlocked BlockedOnSTM  Simon Marlow committed Aug 10, 2010 571  mk_stat 11 = ThreadBlocked BlockedOnForeignCall  Edward Z. Yang committed Jul 09, 2013 572 573 574  mk_stat 12 = ThreadBlocked BlockedOnForeignCall mk_stat 13 = ThreadBlocked BlockedOnException -- NB. these are hardcoded in rts/PrimOps.cmm  Simon Marlow committed Aug 10, 2010 575 576 577  mk_stat 16 = ThreadFinished mk_stat 17 = ThreadDied mk_stat _ = ThreadBlocked BlockedOnOther  Simon Marlow committed Mar 01, 2011 578 579 580 581  -- | returns the number of the capability on which the thread is currently -- running, and a boolean indicating whether the thread is locked to -- that capability or not. A thread is locked to a capability if it  Simon Marlow committed Mar 30, 2011 582 -- was created with @forkOn@.  Herbert Valerio Riedel committed Sep 22, 2013 583 584 -- -- /Since: 4.4.0.0/  Simon Marlow committed Mar 01, 2011 585 586 587 threadCapability :: ThreadId -> IO (Int, Bool) threadCapability (ThreadId t) = IO $\s -> case threadStatus# t s of  Jan Stolarek committed Sep 18, 2013 588  (# s', _, cap#, locked# #) -> (# s', (I# cap#, isTrue# (locked# /=# 0#)) #)  Simon Marlow committed Apr 12, 2012 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604  -- | make a weak pointer to a 'ThreadId'. It can be important to do -- this if you want to hold a reference to a 'ThreadId' while still -- allowing the thread to receive the @BlockedIndefinitely@ family of -- exceptions (e.g. 'BlockedIndefinitelyOnMVar'). Holding a normal -- 'ThreadId' reference will prevent the delivery of -- @BlockedIndefinitely@ exceptions because the reference could be -- used as the target of 'throwTo' at any time, which would unblock -- the thread. -- -- Holding a @Weak ThreadId@, on the other hand, will not prevent the -- thread from receiving @BlockedIndefinitely@ exceptions. It is -- still possible to throw an exception to a @Weak ThreadId@, but the -- caller must use @deRefWeak@ first to determine whether the thread -- still exists. --  Herbert Valerio Riedel committed Sep 21, 2013 605 -- /Since: 4.6.0.0/  Simon Marlow committed Apr 12, 2012 606 607 mkWeakThreadId :: ThreadId -> IO (Weak ThreadId) mkWeakThreadId t@(ThreadId t#) = IO$ \s ->  Simon Marlow committed Apr 27, 2012 608  case mkWeakNoFinalizer# t# t s of  Simon Marlow committed Apr 12, 2012 609  (# s1, w #) -> (# s1, Weak w #)  Simon Marlow committed Aug 10, 2010 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 \end{code} %************************************************************************ %* * \subsection[stm]{Transactional heap operations} %* * %************************************************************************ TVars are shared memory locations which support atomic memory transactions. \begin{code} -- |A monad supporting atomic memory transactions. newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #))  Herbert Valerio Riedel committed Sep 17, 2013 625  deriving Typeable  Simon Marlow committed Aug 10, 2010 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711  unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #)) unSTM (STM a) = a instance Functor STM where fmap f x = x >>= (return . f) instance Monad STM where {-# INLINE return #-} {-# INLINE (>>) #-} {-# INLINE (>>=) #-} m >> k = thenSTM m k return x = returnSTM x m >>= k = bindSTM m k bindSTM :: STM a -> (a -> STM b) -> STM b bindSTM (STM m) k = STM ( \s -> case m s of (# new_s, a #) -> unSTM (k a) new_s ) thenSTM :: STM a -> STM b -> STM b thenSTM (STM m) k = STM ( \s -> case m s of (# new_s, _ #) -> unSTM k new_s ) returnSTM :: a -> STM a returnSTM x = STM (\s -> (# s, x #)) instance MonadPlus STM where mzero = retry mplus = orElse -- | Unsafely performs IO in the STM monad. Beware: this is a highly -- dangerous thing to do. -- -- * The STM implementation will often run transactions multiple -- times, so you need to be prepared for this if your IO has any -- side effects. -- -- * The STM implementation will abort transactions that are known to -- be invalid and need to be restarted. This may happen in the middle -- of unsafeIOToSTM, so make sure you don't acquire any resources -- that need releasing (exception handlers are ignored when aborting -- the transaction). That includes doing any IO using Handles, for -- example. Getting this wrong will probably lead to random deadlocks. -- -- * The transaction may have seen an inconsistent view of memory when -- the IO runs. Invariants that you expect to be true throughout -- your program may not be true inside a transaction, due to the -- way transactions are implemented. Normally this wouldn't be visible -- to the programmer, but using unsafeIOToSTM can expose it. -- unsafeIOToSTM :: IO a -> STM a unsafeIOToSTM (IO m) = STM m -- |Perform a series of STM actions atomically. -- -- You cannot use 'atomically' inside an 'unsafePerformIO' or 'unsafeInterleaveIO'. -- Any attempt to do so will result in a runtime error. (Reason: allowing -- this would effectively allow a transaction inside a transaction, depending -- on exactly when the thunk is evaluated.) -- -- However, see 'newTVarIO', which can be called inside 'unsafePerformIO', -- and which allows top-level TVars to be allocated. atomically :: STM a -> IO a atomically (STM m) = IO (\s -> (atomically# m) s ) -- |Retry execution of the current memory transaction because it has seen -- values in TVars which mean that it should not continue (e.g. the TVars -- represent a shared buffer that is now empty). The implementation may -- block the thread until one of the TVars that it has read from has been -- udpated. (GHC only) retry :: STM a retry = STM $\s# -> retry# s# -- |Compose two alternative STM actions (GHC only). If the first action -- completes without retrying then it forms the result of the orElse. -- Otherwise, if the first action retries, then the second action is -- tried in its place. If both actions retry then the orElse as a -- whole retries. orElse :: STM a -> STM a -> STM a orElse (STM m) e = STM$ \s -> catchRetry# m (unSTM e) s  basvandijk committed Sep 26, 2010 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 -- | A variant of 'throw' that can only be used within the 'STM' monad. -- -- Throwing an exception in @STM@ aborts the transaction and propagates the -- exception. -- -- Although 'throwSTM' has a type that is an instance of the type of 'throw', the -- two functions are subtly different: -- -- > throw e seq x ===> throw e -- > throwSTM e seq x ===> x -- -- The first example will cause the exception @e@ to be raised, -- whereas the second one won\'t. In fact, 'throwSTM' will only cause -- an exception to be raised when it is used within the 'STM' monad. -- The 'throwSTM' variant should be used in preference to 'throw' to -- raise an exception within the 'STM' monad because it guarantees -- ordering with respect to other 'STM' operations, whereas 'throw' -- does not. throwSTM :: Exception e => e -> STM a throwSTM e = STM $raiseIO# (toException e)  Simon Marlow committed Aug 10, 2010 733 -- |Exception handling within STM actions.  basvandijk committed Sep 26, 2010 734 735 736 737 738 739 catchSTM :: Exception e => STM a -> (e -> STM a) -> STM a catchSTM (STM m) handler = STM$ catchSTM# m handler' where handler' e = case fromException e of Just e' -> unSTM (handler e') Nothing -> raiseIO# e  Simon Marlow committed Aug 10, 2010 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762  -- | Low-level primitive on which always and alwaysSucceeds are built. -- checkInv differs form these in that (i) the invariant is not -- checked when checkInv is called, only at the end of this and -- subsequent transcations, (ii) the invariant failure is indicated -- by raising an exception. checkInv :: STM a -> STM () checkInv (STM m) = STM (\s -> (check# m) s) -- | alwaysSucceeds adds a new invariant that must be true when passed -- to alwaysSucceeds, at the end of the current transaction, and at -- the end of every subsequent transaction. If it fails at any -- of those points then the transaction violating it is aborted -- and the exception raised by the invariant is propagated. alwaysSucceeds :: STM a -> STM () alwaysSucceeds i = do ( i >> retry ) orElse ( return () ) checkInv i -- | always is a variant of alwaysSucceeds in which the invariant is -- expressed as an STM Bool action that must return True. Returning -- False or raising an exception are both treated as invariant failures. always :: STM Bool -> STM () always i = alwaysSucceeds ( do v <- i  daniel.is.fischer committed Oct 04, 2011 763  if (v) then return () else ( error "Transactional invariant violation" ) )  Simon Marlow committed Aug 10, 2010 764 765 766  -- |Shared memory locations that support atomic memory transactions. data TVar a = TVar (TVar# RealWorld a)  Herbert Valerio Riedel committed Sep 17, 2013 767  deriving Typeable  Simon Marlow committed Aug 10, 2010 768 769  instance Eq (TVar a) where  Jan Stolarek committed Sep 18, 2013 770  (TVar tvar1#) == (TVar tvar2#) = isTrue# (sameTVar# tvar1# tvar2#)  Simon Marlow committed Aug 10, 2010 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857  -- |Create a new TVar holding a value supplied newTVar :: a -> STM (TVar a) newTVar val = STM $\s1# -> case newTVar# val s1# of (# s2#, tvar# #) -> (# s2#, TVar tvar# #) -- |@IO@ version of 'newTVar'. This is useful for creating top-level -- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using -- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't -- possible. newTVarIO :: a -> IO (TVar a) newTVarIO val = IO$ \s1# -> case newTVar# val s1# of (# s2#, tvar# #) -> (# s2#, TVar tvar# #) -- |Return the current value stored in a TVar. -- This is equivalent to -- -- > readTVarIO = atomically . readTVar -- -- but works much faster, because it doesn't perform a complete -- transaction, it just reads the current value of the 'TVar'. readTVarIO :: TVar a -> IO a readTVarIO (TVar tvar#) = IO $\s# -> readTVarIO# tvar# s# -- |Return the current value stored in a TVar readTVar :: TVar a -> STM a readTVar (TVar tvar#) = STM$ \s# -> readTVar# tvar# s# -- |Write the supplied value into a TVar writeTVar :: TVar a -> a -> STM () writeTVar (TVar tvar#) val = STM $\s1# -> case writeTVar# tvar# val s1# of s2# -> (# s2#, () #) \end{code} MVar utilities \begin{code} withMVar :: MVar a -> (a -> IO b) -> IO b withMVar m io = mask$ \restore -> do a <- takeMVar m b <- catchAny (restore (io a)) (\e -> do putMVar m a; throw e) putMVar m a return b modifyMVar_ :: MVar a -> (a -> IO a) -> IO () modifyMVar_ m io = mask $\restore -> do a <- takeMVar m a' <- catchAny (restore (io a)) (\e -> do putMVar m a; throw e) putMVar m a' return () \end{code} %************************************************************************ %* * \subsection{Thread waiting} %* * %************************************************************************ \begin{code} -- Machinery needed to ensureb that we only have one copy of certain -- CAFs in this module even when the base package is present twice, as -- it is when base is dynamically loaded into GHCi. The RTS keeps -- track of the single true value of the CAF, so even when the CAFs in -- the dynamically-loaded base package are reverted, nothing bad -- happens. -- sharedCAF :: a -> (Ptr a -> IO (Ptr a)) -> IO a sharedCAF a get_or_set = mask_$ do stable_ref <- newStablePtr a let ref = castPtr (castStablePtrToPtr stable_ref) ref2 <- get_or_set ref if ref==ref2 then return a else do freeStablePtr stable_ref deRefStablePtr (castPtrToStablePtr (castPtr ref2)) reportStackOverflow :: IO ()  Ben Gamari committed Oct 25, 2013 858 859 860 reportStackOverflow = do ThreadId tid <- myThreadId callStackOverflowHook tid  Simon Marlow committed Aug 10, 2010 861 862 863 864 865 866 867 868 869  reportError :: SomeException -> IO () reportError ex = do handler <- getUncaughtExceptionHandler handler ex -- SUP: Are the hooks allowed to re-enter Haskell land? If so, remove -- the unsafe below. foreign import ccall unsafe "stackOverflow"  Ben Gamari committed Oct 25, 2013 870  callStackOverflowHook :: ThreadId# -> IO ()  Simon Marlow committed Aug 10, 2010 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899  {-# NOINLINE uncaughtExceptionHandler #-} uncaughtExceptionHandler :: IORef (SomeException -> IO ()) uncaughtExceptionHandler = unsafePerformIO (newIORef defaultHandler) where defaultHandler :: SomeException -> IO () defaultHandler se@(SomeException ex) = do (hFlush stdout) catchAny (\ _ -> return ()) let msg = case cast ex of Just Deadlock -> "no threads to run: infinite loop or deadlock?" _ -> case cast ex of Just (ErrorCall s) -> s _ -> showsPrec 0 se "" withCString "%s" $\cfmt -> withCString msg$ \cmsg -> errorBelch cfmt cmsg -- don't use errorBelch() directly, because we cannot call varargs functions -- using the FFI. foreign import ccall unsafe "HsBase.h errorBelch2" errorBelch :: CString -> CString -> IO () setUncaughtExceptionHandler :: (SomeException -> IO ()) -> IO () setUncaughtExceptionHandler = writeIORef uncaughtExceptionHandler getUncaughtExceptionHandler :: IO (SomeException -> IO ()) getUncaughtExceptionHandler = readIORef uncaughtExceptionHandler \end{code}