1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2004
7 * This file is written in a subset of C--, extended with various
8 * features specific to GHC. It is compiled by GHC directly. For the
9 * syntax of .cmm files, see the parser in ghc/compiler/cmm/CmmParse.y.
11 * ---------------------------------------------------------------------------*/
14 #include "RaiseAsync.h"
16 /* -----------------------------------------------------------------------------
19 A thread can request that asynchronous exceptions not be delivered
20 ("blocked") for the duration of an I/O computation. The primitive
22 blockAsyncExceptions# :: IO a -> IO a
24 is used for this purpose. During a blocked section, asynchronous
25 exceptions may be unblocked again temporarily:
27 unblockAsyncExceptions# :: IO a -> IO a
29 Furthermore, asynchronous exceptions are blocked automatically during
30 the execution of an exception handler. Both of these primitives
31 leave a continuation on the stack which reverts to the previous
32 state (blocked or unblocked) on exit.
34 A thread which wants to raise an exception in another thread (using
35 killThread#) must block until the target thread is ready to receive
36 it. The action of unblocking exceptions in a thread will release all
37 the threads waiting to deliver exceptions to that thread.
39 NB. there's a bug in here. If a thread is inside an
40 unsafePerformIO, and inside blockAsyncExceptions# (there is an
41 unblockAsyncExceptions_ret on the stack), and it is blocked in an
42 interruptible operation, and it receives an exception, then the
43 unsafePerformIO thunk will be updated with a stack object
44 containing the unblockAsyncExceptions_ret frame. Later, when
45 someone else evaluates this thunk, the blocked exception state is
46 not restored, and the result is that unblockAsyncExceptions_ret
47 will attempt to unblock exceptions in the current thread, but it'll
48 find that the CurrentTSO->blocked_exceptions is NULL. Hence, we
49 work around this by checking for NULL in awakenBlockedQueue().
51 -------------------------------------------------------------------------- */
53 INFO_TABLE_RET( stg_unblockAsyncExceptionszh_ret,
54 0/*framesize*/, 0/*bitmap*/, RET_SMALL )
58 // Not true: see comments above
59 // ASSERT(StgTSO_blocked_exceptions(CurrentTSO) != NULL);
61 StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) &
62 ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
64 /* Eagerly raise a blocked exception, if there is one */
65 if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
67 * We have to be very careful here, as in killThread#, since
68 * we are about to raise an async exception in the current
69 * thread, which might result in the thread being killed.
74 * raiseAsync assumes that the stack is in ThreadRunGHC state,
75 * i.e. with a return address on the top. In unreg mode, the
76 * return value for IO is on top of the return address, so we
77 * need to make a small adjustment here.
82 r = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
83 CurrentTSO "ptr") [R1];
86 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
87 jump stg_threadFinished;
90 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
91 jump %ENTRY_CODE(Sp(0));
96 * Readjust stack in unregisterised mode if we didn't raise an
97 * exception, see above
107 jump %ENTRY_CODE(Sp(0));
111 jump %ENTRY_CODE(Sp(1));
115 INFO_TABLE_RET( stg_blockAsyncExceptionszh_ret,
116 0/*framesize*/, 0/*bitmap*/, RET_SMALL )
118 // Not true: see comments above
119 // ASSERT(StgTSO_blocked_exceptions(CurrentTSO) == NULL);
121 StgTSO_flags(CurrentTSO) =
122 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
126 jump %ENTRY_CODE(Sp(0));
130 jump %ENTRY_CODE(Sp(1));
134 blockAsyncExceptionszh_fast
136 /* Args: R1 :: IO a */
137 STK_CHK_GEN( WDS(2)/* worst case */, R1_PTR, blockAsyncExceptionszh_fast);
139 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
141 StgTSO_flags(CurrentTSO) =
142 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
144 /* avoid growing the stack unnecessarily */
145 if (Sp(0) == stg_blockAsyncExceptionszh_ret_info) {
149 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
157 unblockAsyncExceptionszh_fast
161 /* Args: R1 :: IO a */
162 STK_CHK_GEN( WDS(2), R1_PTR, unblockAsyncExceptionszh_fast);
164 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {
166 StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) &
167 ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
169 /* Eagerly raise a blocked exception, if there is one */
170 if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
172 * We have to be very careful here, as in killThread#, since
173 * we are about to raise an async exception in the current
174 * thread, which might result in the thread being killed.
177 r = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
178 CurrentTSO "ptr") [R1];
181 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
182 jump stg_threadFinished;
185 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
186 jump %ENTRY_CODE(Sp(0));
191 /* avoid growing the stack unnecessarily */
192 if (Sp(0) == stg_unblockAsyncExceptionszh_ret_info) {
196 Sp(0) = stg_blockAsyncExceptionszh_ret_info;
207 /* args: R1 = TSO to kill, R2 = Exception */
216 STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, killThreadzh_fast);
219 * We might have killed ourselves. In which case, better be *very*
220 * careful. If the exception killed us, then return to the scheduler.
221 * If the exception went to a catch frame, we'll just continue from
224 if (target == CurrentTSO) {
226 /* ToDo: what if the current thread is blocking exceptions? */
227 foreign "C" throwToSingleThreaded(MyCapability() "ptr",
228 target "ptr", exception "ptr")[R1,R2];
229 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
230 jump stg_threadFinished;
233 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
234 jump %ENTRY_CODE(Sp(0));
239 out = BaseReg + OFFSET_StgRegTable_rmp_tmp_w;
241 retcode = foreign "C" throwTo(MyCapability() "ptr",
247 switch [THROWTO_SUCCESS .. THROWTO_BLOCKED] (retcode) {
249 case THROWTO_SUCCESS: {
250 jump %ENTRY_CODE(Sp(0));
253 case THROWTO_BLOCKED: {
255 // we must block, and call throwToReleaseTarget() before returning
256 jump stg_block_throwto;
262 /* -----------------------------------------------------------------------------
264 -------------------------------------------------------------------------- */
272 #if defined(PROFILING)
273 #define CATCH_FRAME_BITMAP 7
274 #define CATCH_FRAME_WORDS 4
276 #define CATCH_FRAME_BITMAP 1
277 #define CATCH_FRAME_WORDS 2
280 /* Catch frames are very similar to update frames, but when entering
281 * one we just pop the frame off the stack and perform the correct
282 * kind of return to the activation record underneath us on the stack.
285 INFO_TABLE_RET(stg_catch_frame,
286 CATCH_FRAME_WORDS, CATCH_FRAME_BITMAP,
290 Sp = Sp + SIZEOF_StgCatchFrame;
291 jump %ENTRY_CODE(Sp(SP_OFF));
297 Sp = Sp + SIZEOF_StgCatchFrame;
299 jump %ENTRY_CODE(Sp(SP_OFF));
303 /* -----------------------------------------------------------------------------
304 * The catch infotable
306 * This should be exactly the same as would be generated by this STG code
308 * catch = {x,h} \n {} -> catch#{x,h}
310 * It is used in deleteThread when reverting blackholes.
311 * -------------------------------------------------------------------------- */
313 INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
315 R2 = StgClosure_payload(R1,1); /* h */
316 R1 = StgClosure_payload(R1,0); /* x */
322 /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
323 STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, catchzh_fast);
325 /* Set up the catch frame */
326 Sp = Sp - SIZEOF_StgCatchFrame;
327 SET_HDR(Sp,stg_catch_frame_info,W_[CCCS]);
329 StgCatchFrame_handler(Sp) = R2;
330 StgCatchFrame_exceptions_blocked(Sp) = TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX;
331 TICK_CATCHF_PUSHED();
333 /* Apply R1 to the realworld token */
339 /* -----------------------------------------------------------------------------
340 * The raise infotable
342 * This should be exactly the same as would be generated by this STG code
344 * raise = {err} \n {} -> raise#{err}
346 * It is used in raisezh_fast to update thunks on the update list
347 * -------------------------------------------------------------------------- */
349 INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
351 R1 = StgThunk_payload(R1,0);
356 no_break_on_exception: W_[1];
359 INFO_TABLE_RET(stg_raise_ret, 1, 0, RET_SMALL)
363 W_[no_break_on_exception] = 1;
372 /* args : R1 :: Exception */
376 #if defined(PROFILING)
377 /* Debugging tool: on raising an exception, show where we are. */
379 /* ToDo: currently this is a hack. Would be much better if
380 * the info was only displayed for an *uncaught* exception.
382 if (RtsFlags_ProfFlags_showCCSOnException(RtsFlags) != 0::I32) {
383 foreign "C" fprintCCS_stderr(W_[CCCS] "ptr") [];
387 /* Inform the Hpc that an exception has been thrown */
388 foreign "C" hs_hpc_raise_event(CurrentTSO "ptr") [];
391 StgTSO_sp(CurrentTSO) = Sp;
392 frame_type = foreign "C" raiseExceptionHelper(BaseReg "ptr", CurrentTSO "ptr", exception "ptr") [];
393 Sp = StgTSO_sp(CurrentTSO);
394 if (frame_type == ATOMICALLY_FRAME) {
395 /* The exception has reached the edge of a memory transaction. Check that
396 * the transaction is valid. If not then perhaps the exception should
397 * not have been thrown: re-run the transaction. "trec" will either be
398 * a top-level transaction running the atomic block, or a nested
399 * transaction running an invariant check. In the latter case we
400 * abort and de-allocate the top-level transaction that encloses it
401 * as well (we could just abandon its transaction record, but this makes
402 * sure it's marked as aborted and available for re-use). */
405 trec = StgTSO_trec(CurrentTSO);
406 r = foreign "C" stmValidateNestOfTransactions(trec "ptr") [];
407 "ptr" outer = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
408 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
409 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
411 if (outer != NO_TREC) {
412 foreign "C" stmAbortTransaction(MyCapability() "ptr", outer "ptr") [];
413 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", outer "ptr") [];
416 StgTSO_trec(CurrentTSO) = NO_TREC;
418 // Transaction was valid: continue searching for a catch frame
419 Sp = Sp + SIZEOF_StgAtomicallyFrame;
420 goto retry_pop_stack;
422 // Transaction was not valid: we retry the exception (otherwise continue
423 // with a further call to raiseExceptionHelper)
424 "ptr" trec = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr") [];
425 StgTSO_trec(CurrentTSO) = trec;
426 R1 = StgAtomicallyFrame_code(Sp);
431 // After stripping the stack, see whether we should break here for
432 // GHCi (c.f. the -fbreak-on-exception flag). We do this after
433 // stripping the stack for a reason: we'll be inspecting values in
434 // GHCi, and it helps if all the thunks under evaluation have
435 // already been updated with the exception, rather than being left
437 if (W_[no_break_on_exception] != 0) {
438 W_[no_break_on_exception] = 0;
440 if (TO_W_(CInt[rts_stop_on_exception]) != 0) {
442 // we don't want any further exceptions to be caught,
443 // until GHCi is ready to handle them. This prevents
444 // deadlock if an exception is raised in InteractiveUI,
445 // for exmplae. Perhaps the stop_on_exception flag should
447 W_[rts_stop_on_exception] = 0;
448 "ptr" ioAction = foreign "C" deRefStablePtr (W_[rts_breakpoint_io_action] "ptr") [];
451 Sp(4) = stg_raise_ret_info;
452 Sp(3) = exception; // the AP_STACK
453 Sp(2) = base_GHCziBase_True_closure; // dummy breakpoint info
454 Sp(1) = base_GHCziBase_True_closure; // True <=> a breakpoint
456 jump stg_ap_pppv_info;
460 if (frame_type == STOP_FRAME) {
462 * We've stripped the entire stack, the thread is now dead.
463 * We will leave the stack in a GC'able state, see the stg_stop_thread
464 * entry code in StgStartup.cmm.
466 Sp = CurrentTSO + TSO_OFFSET_StgTSO_stack
467 + WDS(TO_W_(StgTSO_stack_size(CurrentTSO))) - WDS(2);
468 Sp(1) = exception; /* save the exception */
469 Sp(0) = stg_enter_info; /* so that GC can traverse this stack */
470 StgTSO_what_next(CurrentTSO) = ThreadKilled::I16;
471 SAVE_THREAD_STATE(); /* inline! */
473 jump stg_threadFinished;
476 /* Ok, Sp points to the enclosing CATCH_FRAME or CATCH_STM_FRAME. Pop everything
477 * down to and including this frame, update Su, push R1, and enter the handler.
479 if (frame_type == CATCH_FRAME) {
480 handler = StgCatchFrame_handler(Sp);
482 handler = StgCatchSTMFrame_handler(Sp);
485 /* Restore the blocked/unblocked state for asynchronous exceptions
486 * at the CATCH_FRAME.
488 * If exceptions were unblocked, arrange that they are unblocked
489 * again after executing the handler by pushing an
490 * unblockAsyncExceptions_ret stack frame.
492 * If we've reached an STM catch frame then roll back the nested
493 * transaction we were using.
497 if (frame_type == CATCH_FRAME) {
498 Sp = Sp + SIZEOF_StgCatchFrame;
499 if (StgCatchFrame_exceptions_blocked(frame) == 0) {
501 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
505 trec = StgTSO_trec(CurrentTSO);
506 "ptr" outer = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
507 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
508 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
509 StgTSO_trec(CurrentTSO) = outer;
510 Sp = Sp + SIZEOF_StgCatchSTMFrame;
513 /* Ensure that async excpetions are blocked when running the handler.
515 StgTSO_flags(CurrentTSO) =
516 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
518 /* Call the handler, passing the exception value and a realworld
519 * token as arguments.
527 jump RET_LBL(stg_ap_pv);
532 /* Args :: R1 :: Exception */