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"
17 import base_GHCziBase_True_closure;
20 /* -----------------------------------------------------------------------------
23 A thread can request that asynchronous exceptions not be delivered
24 ("blocked") for the duration of an I/O computation. The primitive
26 blockAsyncExceptions# :: IO a -> IO a
28 is used for this purpose. During a blocked section, asynchronous
29 exceptions may be unblocked again temporarily:
31 unblockAsyncExceptions# :: IO a -> IO a
33 Furthermore, asynchronous exceptions are blocked automatically during
34 the execution of an exception handler. Both of these primitives
35 leave a continuation on the stack which reverts to the previous
36 state (blocked or unblocked) on exit.
38 A thread which wants to raise an exception in another thread (using
39 killThread#) must block until the target thread is ready to receive
40 it. The action of unblocking exceptions in a thread will release all
41 the threads waiting to deliver exceptions to that thread.
43 NB. there's a bug in here. If a thread is inside an
44 unsafePerformIO, and inside blockAsyncExceptions# (there is an
45 unblockAsyncExceptions_ret on the stack), and it is blocked in an
46 interruptible operation, and it receives an exception, then the
47 unsafePerformIO thunk will be updated with a stack object
48 containing the unblockAsyncExceptions_ret frame. Later, when
49 someone else evaluates this thunk, the blocked exception state is
52 -------------------------------------------------------------------------- */
54 INFO_TABLE_RET( stg_unblockAsyncExceptionszh_ret, RET_SMALL )
58 StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) &
59 ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
61 /* Eagerly raise a blocked exception, if there is one */
62 if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
64 * We have to be very careful here, as in killThread#, since
65 * we are about to raise an async exception in the current
66 * thread, which might result in the thread being killed.
71 * raiseAsync assumes that the stack is in ThreadRunGHC state,
72 * i.e. with a return address on the top. In unreg mode, the
73 * return value for IO is on top of the return address, so we
74 * need to make a small adjustment here.
79 (r) = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
80 CurrentTSO "ptr") [R1];
83 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
84 jump stg_threadFinished;
87 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
88 jump %ENTRY_CODE(Sp(0));
93 * Readjust stack in unregisterised mode if we didn't raise an
94 * exception, see above
104 jump %ENTRY_CODE(Sp(0));
108 jump %ENTRY_CODE(Sp(1));
112 INFO_TABLE_RET( stg_blockAsyncExceptionszh_ret, RET_SMALL )
114 StgTSO_flags(CurrentTSO) =
115 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
119 jump %ENTRY_CODE(Sp(0));
123 jump %ENTRY_CODE(Sp(1));
127 blockAsyncExceptionszh_fast
129 /* Args: R1 :: IO a */
130 STK_CHK_GEN( WDS(2)/* worst case */, R1_PTR, blockAsyncExceptionszh_fast);
132 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
134 StgTSO_flags(CurrentTSO) =
135 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
137 /* avoid growing the stack unnecessarily */
138 if (Sp(0) == stg_blockAsyncExceptionszh_ret_info) {
142 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
150 unblockAsyncExceptionszh_fast
154 /* Args: R1 :: IO a */
155 STK_CHK_GEN( WDS(2), R1_PTR, unblockAsyncExceptionszh_fast);
157 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {
159 StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) &
160 ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
162 /* Eagerly raise a blocked exception, if there is one */
163 if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
165 * We have to be very careful here, as in killThread#, since
166 * we are about to raise an async exception in the current
167 * thread, which might result in the thread being killed.
170 (r) = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
171 CurrentTSO "ptr") [R1];
174 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
175 jump stg_threadFinished;
178 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
179 jump %ENTRY_CODE(Sp(0));
184 /* avoid growing the stack unnecessarily */
185 if (Sp(0) == stg_unblockAsyncExceptionszh_ret_info) {
189 Sp(0) = stg_blockAsyncExceptionszh_ret_info;
200 /* args: R1 = TSO to kill, R2 = Exception */
209 STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, killThreadzh_fast);
212 * We might have killed ourselves. In which case, better be *very*
213 * careful. If the exception killed us, then return to the scheduler.
214 * If the exception went to a catch frame, we'll just continue from
218 if (StgTSO_what_next(target) == ThreadRelocated::I16) {
219 target = StgTSO_link(target);
222 if (target == CurrentTSO) {
224 /* ToDo: what if the current thread is blocking exceptions? */
225 foreign "C" throwToSingleThreaded(MyCapability() "ptr",
226 target "ptr", exception "ptr")[R1,R2];
227 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
228 jump stg_threadFinished;
231 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
232 jump %ENTRY_CODE(Sp(0));
237 out = BaseReg + OFFSET_StgRegTable_rmp_tmp_w;
239 (retcode) = foreign "C" throwTo(MyCapability() "ptr",
245 switch [THROWTO_SUCCESS .. THROWTO_BLOCKED] (retcode) {
247 case THROWTO_SUCCESS: {
248 jump %ENTRY_CODE(Sp(0));
251 case THROWTO_BLOCKED: {
253 // we must block, and call throwToReleaseTarget() before returning
254 jump stg_block_throwto;
260 /* -----------------------------------------------------------------------------
262 -------------------------------------------------------------------------- */
270 /* Catch frames are very similar to update frames, but when entering
271 * one we just pop the frame off the stack and perform the correct
272 * kind of return to the activation record underneath us on the stack.
275 INFO_TABLE_RET(stg_catch_frame, CATCH_FRAME,
276 #if defined(PROFILING)
277 W_ unused1, W_ unused2,
279 W_ unused3, "ptr" W_ unused4)
282 Sp = Sp + SIZEOF_StgCatchFrame;
283 jump %ENTRY_CODE(Sp(SP_OFF));
289 Sp = Sp + SIZEOF_StgCatchFrame;
291 jump %ENTRY_CODE(Sp(SP_OFF));
295 /* -----------------------------------------------------------------------------
296 * The catch infotable
298 * This should be exactly the same as would be generated by this STG code
300 * catch = {x,h} \n {} -> catch#{x,h}
302 * It is used in deleteThread when reverting blackholes.
303 * -------------------------------------------------------------------------- */
305 INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
307 R2 = StgClosure_payload(R1,1); /* h */
308 R1 = StgClosure_payload(R1,0); /* x */
314 /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
315 STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, catchzh_fast);
317 /* Set up the catch frame */
318 Sp = Sp - SIZEOF_StgCatchFrame;
319 SET_HDR(Sp,stg_catch_frame_info,W_[CCCS]);
321 StgCatchFrame_handler(Sp) = R2;
322 StgCatchFrame_exceptions_blocked(Sp) = TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX;
323 TICK_CATCHF_PUSHED();
325 /* Apply R1 to the realworld token */
331 /* -----------------------------------------------------------------------------
332 * The raise infotable
334 * This should be exactly the same as would be generated by this STG code
336 * raise = {err} \n {} -> raise#{err}
338 * It is used in raisezh_fast to update thunks on the update list
339 * -------------------------------------------------------------------------- */
341 INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
343 R1 = StgThunk_payload(R1,0);
348 no_break_on_exception: W_[1];
351 INFO_TABLE_RET(stg_raise_ret, RET_SMALL, "ptr" W_ arg1)
355 W_[no_break_on_exception] = 1;
364 /* args : R1 :: Exception */
368 #if defined(PROFILING)
369 /* Debugging tool: on raising an exception, show where we are. */
371 /* ToDo: currently this is a hack. Would be much better if
372 * the info was only displayed for an *uncaught* exception.
374 if (RtsFlags_ProfFlags_showCCSOnException(RtsFlags) != 0::I32) {
375 foreign "C" fprintCCS_stderr(W_[CCCS] "ptr") [];
380 StgTSO_sp(CurrentTSO) = Sp;
381 (frame_type) = foreign "C" raiseExceptionHelper(BaseReg "ptr", CurrentTSO "ptr", exception "ptr") [];
382 Sp = StgTSO_sp(CurrentTSO);
383 if (frame_type == ATOMICALLY_FRAME) {
384 /* The exception has reached the edge of a memory transaction. Check that
385 * the transaction is valid. If not then perhaps the exception should
386 * not have been thrown: re-run the transaction. "trec" will either be
387 * a top-level transaction running the atomic block, or a nested
388 * transaction running an invariant check. In the latter case we
389 * abort and de-allocate the top-level transaction that encloses it
390 * as well (we could just abandon its transaction record, but this makes
391 * sure it's marked as aborted and available for re-use). */
394 trec = StgTSO_trec(CurrentTSO);
395 (r) = foreign "C" stmValidateNestOfTransactions(trec "ptr") [];
396 ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
397 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
398 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
400 if (outer != NO_TREC) {
401 foreign "C" stmAbortTransaction(MyCapability() "ptr", outer "ptr") [];
402 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", outer "ptr") [];
405 StgTSO_trec(CurrentTSO) = NO_TREC;
407 // Transaction was valid: continue searching for a catch frame
408 Sp = Sp + SIZEOF_StgAtomicallyFrame;
409 goto retry_pop_stack;
411 // Transaction was not valid: we retry the exception (otherwise continue
412 // with a further call to raiseExceptionHelper)
413 ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr") [];
414 StgTSO_trec(CurrentTSO) = trec;
415 R1 = StgAtomicallyFrame_code(Sp);
420 // After stripping the stack, see whether we should break here for
421 // GHCi (c.f. the -fbreak-on-exception flag). We do this after
422 // stripping the stack for a reason: we'll be inspecting values in
423 // GHCi, and it helps if all the thunks under evaluation have
424 // already been updated with the exception, rather than being left
426 if (W_[no_break_on_exception] != 0) {
427 W_[no_break_on_exception] = 0;
429 if (TO_W_(CInt[rts_stop_on_exception]) != 0) {
431 // we don't want any further exceptions to be caught,
432 // until GHCi is ready to handle them. This prevents
433 // deadlock if an exception is raised in InteractiveUI,
434 // for exmplae. Perhaps the stop_on_exception flag should
436 W_[rts_stop_on_exception] = 0;
437 ("ptr" ioAction) = foreign "C" deRefStablePtr (W_[rts_breakpoint_io_action] "ptr") [];
440 Sp(5) = stg_raise_ret_info;
441 Sp(4) = stg_noforceIO_info; // required for unregisterised
442 Sp(3) = exception; // the AP_STACK
443 Sp(2) = base_GHCziBase_True_closure; // dummy breakpoint info
444 Sp(1) = base_GHCziBase_True_closure; // True <=> a breakpoint
446 jump RET_LBL(stg_ap_pppv);
450 if (frame_type == STOP_FRAME) {
452 * We've stripped the entire stack, the thread is now dead.
453 * We will leave the stack in a GC'able state, see the stg_stop_thread
454 * entry code in StgStartup.cmm.
456 Sp = CurrentTSO + TSO_OFFSET_StgTSO_stack
457 + WDS(TO_W_(StgTSO_stack_size(CurrentTSO))) - WDS(2);
458 Sp(1) = exception; /* save the exception */
459 Sp(0) = stg_enter_info; /* so that GC can traverse this stack */
460 StgTSO_what_next(CurrentTSO) = ThreadKilled::I16;
461 SAVE_THREAD_STATE(); /* inline! */
463 jump stg_threadFinished;
466 /* Ok, Sp points to the enclosing CATCH_FRAME or CATCH_STM_FRAME. Pop everything
467 * down to and including this frame, update Su, push R1, and enter the handler.
469 if (frame_type == CATCH_FRAME) {
470 handler = StgCatchFrame_handler(Sp);
472 handler = StgCatchSTMFrame_handler(Sp);
475 /* Restore the blocked/unblocked state for asynchronous exceptions
476 * at the CATCH_FRAME.
478 * If exceptions were unblocked, arrange that they are unblocked
479 * again after executing the handler by pushing an
480 * unblockAsyncExceptions_ret stack frame.
482 * If we've reached an STM catch frame then roll back the nested
483 * transaction we were using.
487 if (frame_type == CATCH_FRAME) {
488 Sp = Sp + SIZEOF_StgCatchFrame;
489 if (StgCatchFrame_exceptions_blocked(frame) == 0) {
491 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
495 trec = StgTSO_trec(CurrentTSO);
496 ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
497 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
498 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
499 StgTSO_trec(CurrentTSO) = outer;
500 Sp = Sp + SIZEOF_StgCatchSTMFrame;
503 /* Ensure that async excpetions are blocked when running the handler.
505 StgTSO_flags(CurrentTSO) =
506 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
508 /* Call the handler, passing the exception value and a realworld
509 * token as arguments.
517 jump RET_LBL(stg_ap_pv);
522 /* Args :: R1 :: Exception */