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 import ghczmprim_GHCziTypes_True_closure;
18 /* -----------------------------------------------------------------------------
21 A thread can request that asynchronous exceptions not be delivered
22 ("blocked") for the duration of an I/O computation. The primitive
24 maskAsyncExceptions# :: IO a -> IO a
26 is used for this purpose. During a blocked section, asynchronous
27 exceptions may be unblocked again temporarily:
29 unmaskAsyncExceptions# :: IO a -> IO a
31 Furthermore, asynchronous exceptions are blocked automatically during
32 the execution of an exception handler. Both of these primitives
33 leave a continuation on the stack which reverts to the previous
34 state (blocked or unblocked) on exit.
36 A thread which wants to raise an exception in another thread (using
37 killThread#) must block until the target thread is ready to receive
38 it. The action of unblocking exceptions in a thread will release all
39 the threads waiting to deliver exceptions to that thread.
41 NB. there's a bug in here. If a thread is inside an
42 unsafePerformIO, and inside maskAsyncExceptions# (there is an
43 unmaskAsyncExceptions_ret on the stack), and it is blocked in an
44 interruptible operation, and it receives an exception, then the
45 unsafePerformIO thunk will be updated with a stack object
46 containing the unmaskAsyncExceptions_ret frame. Later, when
47 someone else evaluates this thunk, the blocked exception state is
50 -------------------------------------------------------------------------- */
53 INFO_TABLE_RET(stg_unmaskAsyncExceptionszh_ret, RET_SMALL)
57 StgTSO_flags(CurrentTSO) = %lobits32(
58 TO_W_(StgTSO_flags(CurrentTSO)) & ~(TSO_BLOCKEX|TSO_INTERRUPTIBLE));
60 /* Eagerly raise a blocked exception, if there is one */
61 if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
63 STK_CHK_GEN( WDS(2), R1_PTR, stg_unmaskAsyncExceptionszh_ret_info);
65 * We have to be very careful here, as in killThread#, since
66 * we are about to raise an async exception in the current
67 * thread, which might result in the thread being killed.
71 Sp(0) = stg_gc_unpt_r1_info;
73 (r) = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
74 CurrentTSO "ptr") [R1];
77 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
78 jump stg_threadFinished;
81 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
82 jump %ENTRY_CODE(Sp(0));
87 the thread might have been removed from the
88 blocked_exception list by someone else in the meantime.
89 Just restore the stack pointer and continue.
96 jump %ENTRY_CODE(Sp(0));
99 INFO_TABLE_RET(stg_maskAsyncExceptionszh_ret, RET_SMALL)
101 StgTSO_flags(CurrentTSO) =
103 TO_W_(StgTSO_flags(CurrentTSO))
104 | TSO_BLOCKEX | TSO_INTERRUPTIBLE
108 jump %ENTRY_CODE(Sp(0));
111 INFO_TABLE_RET(stg_maskUninterruptiblezh_ret, RET_SMALL)
113 StgTSO_flags(CurrentTSO) =
115 (TO_W_(StgTSO_flags(CurrentTSO))
121 jump %ENTRY_CODE(Sp(0));
124 stg_maskAsyncExceptionszh
126 /* Args: R1 :: IO a */
127 STK_CHK_GEN( WDS(1)/* worst case */, R1_PTR, stg_maskAsyncExceptionszh);
129 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
130 /* avoid growing the stack unnecessarily */
131 if (Sp(0) == stg_maskAsyncExceptionszh_ret_info) {
135 Sp(0) = stg_unmaskAsyncExceptionszh_ret_info;
138 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) == 0) {
140 Sp(0) = stg_maskUninterruptiblezh_ret_info;
144 StgTSO_flags(CurrentTSO) = %lobits32(
145 TO_W_(StgTSO_flags(CurrentTSO)) | TSO_BLOCKEX | TSO_INTERRUPTIBLE);
152 stg_maskUninterruptiblezh
154 /* Args: R1 :: IO a */
155 STK_CHK_GEN( WDS(1)/* worst case */, R1_PTR, stg_maskAsyncExceptionszh);
157 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
158 /* avoid growing the stack unnecessarily */
159 if (Sp(0) == stg_maskUninterruptiblezh_ret_info) {
163 Sp(0) = stg_unmaskAsyncExceptionszh_ret_info;
166 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) != 0) {
168 Sp(0) = stg_maskAsyncExceptionszh_ret_info;
172 StgTSO_flags(CurrentTSO) = %lobits32(
173 (TO_W_(StgTSO_flags(CurrentTSO)) | TSO_BLOCKEX) & ~TSO_INTERRUPTIBLE);
180 stg_unmaskAsyncExceptionszh
185 /* Args: R1 :: IO a */
186 STK_CHK_GEN( WDS(4), R1_PTR, stg_unmaskAsyncExceptionszh);
187 /* 4 words: one for the unblock frame, 3 for setting up the
188 * stack to call maybePerformBlockedException() below.
191 /* If exceptions are already unblocked, there's nothing to do */
192 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {
194 /* avoid growing the stack unnecessarily */
195 if (Sp(0) == stg_unmaskAsyncExceptionszh_ret_info) {
199 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) != 0) {
200 Sp(0) = stg_maskAsyncExceptionszh_ret_info;
202 Sp(0) = stg_maskUninterruptiblezh_ret_info;
206 StgTSO_flags(CurrentTSO) = %lobits32(
207 TO_W_(StgTSO_flags(CurrentTSO)) & ~(TSO_BLOCKEX|TSO_INTERRUPTIBLE));
209 /* Eagerly raise a blocked exception, if there is one */
210 if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
212 * We have to be very careful here, as in killThread#, since
213 * we are about to raise an async exception in the current
214 * thread, which might result in the thread being killed.
216 * Now, if we are to raise an exception in the current
217 * thread, there might be an update frame above us on the
218 * stack due to unsafePerformIO. Hence, the stack must
219 * make sense, because it is about to be snapshotted into
223 Sp(2) = stg_ap_v_info;
225 Sp(0) = stg_enter_info;
228 (r) = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
229 CurrentTSO "ptr") [R1];
232 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
233 jump stg_threadFinished;
236 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
237 jump %ENTRY_CODE(Sp(0));
240 /* we'll just call R1 directly, below */
252 stg_getMaskingStatezh
256 returns: 0 == unmasked,
257 1 == masked, non-interruptible,
258 2 == masked, interruptible
260 RET_N(((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) +
261 ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) != 0));
266 /* args: R1 = TSO to kill, R2 = Exception */
275 /* Needs 3 words because throwToSingleThreaded uses some stack */
276 STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, stg_killThreadzh);
277 /* We call allocate in throwTo(), so better check for GC */
278 MAYBE_GC(R1_PTR & R2_PTR, stg_killThreadzh);
281 * We might have killed ourselves. In which case, better be *very*
282 * careful. If the exception killed us, then return to the scheduler.
283 * If the exception went to a catch frame, we'll just continue from
286 if (target == CurrentTSO) {
288 * So what should happen if a thread calls "throwTo self" inside
289 * unsafePerformIO, and later the closure is evaluated by another
290 * thread? Presumably it should behave as if throwTo just returned,
291 * and then continue from there. See #3279, #3288. This is what
292 * happens: on resumption, we will just jump to the next frame on
293 * the stack, which is the return point for stg_killThreadzh.
296 /* ToDo: what if the current thread is blocking exceptions? */
297 foreign "C" throwToSingleThreaded(MyCapability() "ptr",
298 target "ptr", exception "ptr")[R1,R2];
299 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
300 jump stg_threadFinished;
303 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
304 jump %ENTRY_CODE(Sp(0));
309 out = Sp - WDS(1); /* ok to re-use stack space here */
311 (msg) = foreign "C" throwTo(MyCapability() "ptr",
314 exception "ptr") [R1,R2];
317 jump %ENTRY_CODE(Sp(0));
319 StgTSO_why_blocked(CurrentTSO) = BlockedOnMsgThrowTo;
320 StgTSO_block_info(CurrentTSO) = msg;
321 // we must block, and unlock the message before returning
322 jump stg_block_throwto;
327 /* -----------------------------------------------------------------------------
329 -------------------------------------------------------------------------- */
333 /* Catch frames are very similar to update frames, but when entering
334 * one we just pop the frame off the stack and perform the correct
335 * kind of return to the activation record underneath us on the stack.
338 INFO_TABLE_RET(stg_catch_frame, CATCH_FRAME,
339 #if defined(PROFILING)
340 W_ unused1, W_ unused2,
342 W_ unused3, P_ unused4)
344 Sp = Sp + SIZEOF_StgCatchFrame;
345 jump %ENTRY_CODE(Sp(SP_OFF));
348 /* -----------------------------------------------------------------------------
349 * The catch infotable
351 * This should be exactly the same as would be generated by this STG code
353 * catch = {x,h} \n {} -> catch#{x,h}
355 * It is used in deleteThread when reverting blackholes.
356 * -------------------------------------------------------------------------- */
358 INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
360 R2 = StgClosure_payload(R1,1); /* h */
361 R1 = StgClosure_payload(R1,0); /* x */
367 /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
368 STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, stg_catchzh);
370 /* Set up the catch frame */
371 Sp = Sp - SIZEOF_StgCatchFrame;
372 SET_HDR(Sp,stg_catch_frame_info,W_[CCCS]);
374 StgCatchFrame_handler(Sp) = R2;
375 StgCatchFrame_exceptions_blocked(Sp) =
376 TO_W_(StgTSO_flags(CurrentTSO)) & (TSO_BLOCKEX | TSO_INTERRUPTIBLE);
377 TICK_CATCHF_PUSHED();
379 /* Apply R1 to the realworld token */
385 /* -----------------------------------------------------------------------------
386 * The raise infotable
388 * This should be exactly the same as would be generated by this STG code
390 * raise = {err} \n {} -> raise#{err}
392 * It is used in stg_raisezh to update thunks on the update list
393 * -------------------------------------------------------------------------- */
395 INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
397 R1 = StgThunk_payload(R1,0);
402 no_break_on_exception: W_[1];
405 INFO_TABLE_RET(stg_raise_ret, RET_SMALL, P_ arg1)
409 W_[no_break_on_exception] = 1;
418 /* args : R1 :: Exception */
422 #if defined(PROFILING)
423 /* Debugging tool: on raising an exception, show where we are. */
425 /* ToDo: currently this is a hack. Would be much better if
426 * the info was only displayed for an *uncaught* exception.
428 if (RtsFlags_ProfFlags_showCCSOnException(RtsFlags) != 0::I32) {
429 foreign "C" fprintCCS_stderr(W_[CCCS] "ptr") [];
435 (frame_type) = foreign "C" raiseExceptionHelper(BaseReg "ptr", CurrentTSO "ptr", exception "ptr") [];
437 if (frame_type == ATOMICALLY_FRAME) {
438 /* The exception has reached the edge of a memory transaction. Check that
439 * the transaction is valid. If not then perhaps the exception should
440 * not have been thrown: re-run the transaction. "trec" will either be
441 * a top-level transaction running the atomic block, or a nested
442 * transaction running an invariant check. In the latter case we
443 * abort and de-allocate the top-level transaction that encloses it
444 * as well (we could just abandon its transaction record, but this makes
445 * sure it's marked as aborted and available for re-use). */
448 trec = StgTSO_trec(CurrentTSO);
449 (r) = foreign "C" stmValidateNestOfTransactions(trec "ptr") [];
450 outer = StgTRecHeader_enclosing_trec(trec);
451 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
452 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
454 if (outer != NO_TREC) {
455 foreign "C" stmAbortTransaction(MyCapability() "ptr", outer "ptr") [];
456 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", outer "ptr") [];
459 StgTSO_trec(CurrentTSO) = NO_TREC;
461 // Transaction was valid: continue searching for a catch frame
462 Sp = Sp + SIZEOF_StgAtomicallyFrame;
463 goto retry_pop_stack;
465 // Transaction was not valid: we retry the exception (otherwise continue
466 // with a further call to raiseExceptionHelper)
467 ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr") [];
468 StgTSO_trec(CurrentTSO) = trec;
469 R1 = StgAtomicallyFrame_code(Sp);
474 // After stripping the stack, see whether we should break here for
475 // GHCi (c.f. the -fbreak-on-exception flag). We do this after
476 // stripping the stack for a reason: we'll be inspecting values in
477 // GHCi, and it helps if all the thunks under evaluation have
478 // already been updated with the exception, rather than being left
480 if (W_[no_break_on_exception] != 0) {
481 W_[no_break_on_exception] = 0;
483 if (TO_W_(CInt[rts_stop_on_exception]) != 0) {
485 // we don't want any further exceptions to be caught,
486 // until GHCi is ready to handle them. This prevents
487 // deadlock if an exception is raised in InteractiveUI,
488 // for exmplae. Perhaps the stop_on_exception flag should
490 CInt[rts_stop_on_exception] = 0;
491 ("ptr" ioAction) = foreign "C" deRefStablePtr (W_[rts_breakpoint_io_action] "ptr") [];
494 Sp(4) = stg_raise_ret_info;
495 Sp(3) = exception; // the AP_STACK
496 Sp(2) = ghczmprim_GHCziTypes_True_closure; // dummy breakpoint info
497 Sp(1) = ghczmprim_GHCziTypes_True_closure; // True <=> a breakpoint
499 jump RET_LBL(stg_ap_pppv);
503 if (frame_type == STOP_FRAME) {
505 * We've stripped the entire stack, the thread is now dead.
506 * We will leave the stack in a GC'able state, see the stg_stop_thread
507 * entry code in StgStartup.cmm.
510 stack = StgTSO_stackobj(CurrentTSO);
511 Sp = stack + OFFSET_StgStack_stack
512 + WDS(TO_W_(StgStack_stack_size(stack))) - WDS(2);
513 Sp(1) = exception; /* save the exception */
514 Sp(0) = stg_enter_info; /* so that GC can traverse this stack */
515 StgTSO_what_next(CurrentTSO) = ThreadKilled::I16;
516 SAVE_THREAD_STATE(); /* inline! */
518 jump stg_threadFinished;
521 /* Ok, Sp points to the enclosing CATCH_FRAME or CATCH_STM_FRAME. Pop everything
522 * down to and including this frame, update Su, push R1, and enter the handler.
524 if (frame_type == CATCH_FRAME) {
525 handler = StgCatchFrame_handler(Sp);
527 handler = StgCatchSTMFrame_handler(Sp);
530 /* Restore the blocked/unblocked state for asynchronous exceptions
531 * at the CATCH_FRAME.
533 * If exceptions were unblocked, arrange that they are unblocked
534 * again after executing the handler by pushing an
535 * unmaskAsyncExceptions_ret stack frame.
537 * If we've reached an STM catch frame then roll back the nested
538 * transaction we were using.
542 if (frame_type == CATCH_FRAME) {
543 Sp = Sp + SIZEOF_StgCatchFrame;
544 if ((StgCatchFrame_exceptions_blocked(frame) & TSO_BLOCKEX) == 0) {
546 Sp(0) = stg_unmaskAsyncExceptionszh_ret_info;
550 trec = StgTSO_trec(CurrentTSO);
551 outer = StgTRecHeader_enclosing_trec(trec);
552 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
553 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
554 StgTSO_trec(CurrentTSO) = outer;
555 Sp = Sp + SIZEOF_StgCatchSTMFrame;
558 /* Ensure that async excpetions are blocked when running the handler.
559 * The interruptible state is inherited from the context of the
562 StgTSO_flags(CurrentTSO) = %lobits32(
563 TO_W_(StgTSO_flags(CurrentTSO)) | TSO_BLOCKEX);
564 if ((StgCatchFrame_exceptions_blocked(frame) & TSO_INTERRUPTIBLE) == 0) {
565 StgTSO_flags(CurrentTSO) = %lobits32(
566 TO_W_(StgTSO_flags(CurrentTSO)) & ~TSO_INTERRUPTIBLE);
568 StgTSO_flags(CurrentTSO) = %lobits32(
569 TO_W_(StgTSO_flags(CurrentTSO)) | TSO_INTERRUPTIBLE);
572 /* Call the handler, passing the exception value and a realworld
573 * token as arguments.
581 jump RET_LBL(stg_ap_pv);
586 /* Args :: R1 :: Exception */