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.
72 r = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
73 CurrentTSO "ptr") [R1];
76 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
81 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
82 jump %ENTRY_CODE(Sp(0));
89 jump %ENTRY_CODE(Sp(0));
93 jump %ENTRY_CODE(Sp(1));
97 INFO_TABLE_RET( stg_blockAsyncExceptionszh_ret,
98 0/*framesize*/, 0/*bitmap*/, RET_SMALL )
100 // Not true: see comments above
101 // ASSERT(StgTSO_blocked_exceptions(CurrentTSO) == NULL);
103 StgTSO_flags(CurrentTSO) =
104 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
108 jump %ENTRY_CODE(Sp(0));
112 jump %ENTRY_CODE(Sp(1));
116 blockAsyncExceptionszh_fast
118 /* Args: R1 :: IO a */
119 STK_CHK_GEN( WDS(2)/* worst case */, R1_PTR, blockAsyncExceptionszh_fast);
121 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
123 StgTSO_flags(CurrentTSO) =
124 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
126 /* avoid growing the stack unnecessarily */
127 if (Sp(0) == stg_blockAsyncExceptionszh_ret_info) {
131 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
139 unblockAsyncExceptionszh_fast
143 /* Args: R1 :: IO a */
144 STK_CHK_GEN( WDS(2), R1_PTR, unblockAsyncExceptionszh_fast);
146 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {
148 StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) &
149 ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
151 /* Eagerly raise a blocked exception, if there is one */
152 if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
154 * We have to be very careful here, as in killThread#, since
155 * we are about to raise an async exception in the current
156 * thread, which might result in the thread being killed.
159 r = foreign "C" maybePerformBlockedException (MyCapability() "ptr",
160 CurrentTSO "ptr") [R1];
163 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
168 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
169 jump %ENTRY_CODE(Sp(0));
174 /* avoid growing the stack unnecessarily */
175 if (Sp(0) == stg_unblockAsyncExceptionszh_ret_info) {
179 Sp(0) = stg_blockAsyncExceptionszh_ret_info;
190 /* args: R1 = TSO to kill, R2 = Exception */
199 STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, killThreadzh_fast);
202 * We might have killed ourselves. In which case, better be *very*
203 * careful. If the exception killed us, then return to the scheduler.
204 * If the exception went to a catch frame, we'll just continue from
207 if (target == CurrentTSO) {
209 /* ToDo: what if the current thread is blocking exceptions? */
210 foreign "C" throwToSingleThreaded(MyCapability() "ptr",
211 target "ptr", exception "ptr")[R1,R2];
212 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
217 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
218 jump %ENTRY_CODE(Sp(0));
223 out = BaseReg + OFFSET_StgRegTable_rmp_tmp_w;
225 retcode = foreign "C" throwTo(MyCapability() "ptr",
231 switch [THROWTO_SUCCESS .. THROWTO_BLOCKED] (retcode) {
233 case THROWTO_SUCCESS: {
234 jump %ENTRY_CODE(Sp(0));
237 case THROWTO_BLOCKED: {
239 // we must block, and call throwToReleaseTarget() before returning
240 jump stg_block_throwto;
246 /* -----------------------------------------------------------------------------
248 -------------------------------------------------------------------------- */
251 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret) \
254 Sp = Sp + SIZEOF_StgCatchFrame; \
258 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret) \
263 Sp = Sp + SIZEOF_StgCatchFrame; \
275 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_0_ret,%RET_VEC(Sp(SP_OFF),0))
276 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_1_ret,%RET_VEC(Sp(SP_OFF),1))
277 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_2_ret,%RET_VEC(Sp(SP_OFF),2))
278 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_3_ret,%RET_VEC(Sp(SP_OFF),3))
279 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_4_ret,%RET_VEC(Sp(SP_OFF),4))
280 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_5_ret,%RET_VEC(Sp(SP_OFF),5))
281 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_6_ret,%RET_VEC(Sp(SP_OFF),6))
282 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_7_ret,%RET_VEC(Sp(SP_OFF),7))
284 #if MAX_VECTORED_RTN > 8
285 #error MAX_VECTORED_RTN has changed: please modify stg_catch_frame too.
288 #if defined(PROFILING)
289 #define CATCH_FRAME_BITMAP 7
290 #define CATCH_FRAME_WORDS 4
292 #define CATCH_FRAME_BITMAP 1
293 #define CATCH_FRAME_WORDS 2
296 /* Catch frames are very similar to update frames, but when entering
297 * one we just pop the frame off the stack and perform the correct
298 * kind of return to the activation record underneath us on the stack.
301 INFO_TABLE_RET(stg_catch_frame,
302 CATCH_FRAME_WORDS, CATCH_FRAME_BITMAP,
304 stg_catch_frame_0_ret,
305 stg_catch_frame_1_ret,
306 stg_catch_frame_2_ret,
307 stg_catch_frame_3_ret,
308 stg_catch_frame_4_ret,
309 stg_catch_frame_5_ret,
310 stg_catch_frame_6_ret,
311 stg_catch_frame_7_ret)
312 CATCH_FRAME_ENTRY_TEMPLATE(,%ENTRY_CODE(Sp(SP_OFF)))
314 /* -----------------------------------------------------------------------------
315 * The catch infotable
317 * This should be exactly the same as would be generated by this STG code
319 * catch = {x,h} \n {} -> catch#{x,h}
321 * It is used in deleteThread when reverting blackholes.
322 * -------------------------------------------------------------------------- */
324 INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
326 R2 = StgClosure_payload(R1,1); /* h */
327 R1 = StgClosure_payload(R1,0); /* x */
333 /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
334 STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, catchzh_fast);
336 /* Set up the catch frame */
337 Sp = Sp - SIZEOF_StgCatchFrame;
338 SET_HDR(Sp,stg_catch_frame_info,W_[CCCS]);
340 StgCatchFrame_handler(Sp) = R2;
341 StgCatchFrame_exceptions_blocked(Sp) = TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX;
342 TICK_CATCHF_PUSHED();
344 /* Apply R1 to the realworld token */
350 /* -----------------------------------------------------------------------------
351 * The raise infotable
353 * This should be exactly the same as would be generated by this STG code
355 * raise = {err} \n {} -> raise#{err}
357 * It is used in raisezh_fast to update thunks on the update list
358 * -------------------------------------------------------------------------- */
360 INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
362 R1 = StgThunk_payload(R1,0);
371 /* args : R1 :: Exception */
374 #if defined(PROFILING)
375 /* Debugging tool: on raising an exception, show where we are. */
377 /* ToDo: currently this is a hack. Would be much better if
378 * the info was only displayed for an *uncaught* exception.
380 if (RtsFlags_ProfFlags_showCCSOnException(RtsFlags) != 0::I32) {
381 foreign "C" fprintCCS_stderr(W_[CCCS] "ptr");
385 /* Inform the Hpc that an exception has been thrown */
386 foreign "C" hs_hpc_raise_event(CurrentTSO "ptr");
389 StgTSO_sp(CurrentTSO) = Sp;
390 frame_type = foreign "C" raiseExceptionHelper(BaseReg "ptr", CurrentTSO "ptr", R1 "ptr");
391 Sp = StgTSO_sp(CurrentTSO);
392 if (frame_type == ATOMICALLY_FRAME) {
393 /* The exception has reached the edge of a memory transaction. Check that
394 * the transaction is valid. If not then perhaps the exception should
395 * not have been thrown: re-run the transaction. "trec" will either be
396 * a top-level transaction running the atomic block, or a nested
397 * transaction running an invariant check. In the latter case we
398 * abort and de-allocate the top-level transaction that encloses it
399 * as well (we could just abandon its transaction record, but this makes
400 * sure it's marked as aborted and available for re-use). */
403 trec = StgTSO_trec(CurrentTSO);
404 r = foreign "C" stmValidateNestOfTransactions(trec "ptr");
405 "ptr" outer = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
406 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr");
407 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr");
409 if (outer != NO_TREC) {
410 foreign "C" stmAbortTransaction(MyCapability() "ptr", outer "ptr");
411 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", outer "ptr");
414 StgTSO_trec(CurrentTSO) = NO_TREC;
416 // Transaction was valid: continue searching for a catch frame
417 Sp = Sp + SIZEOF_StgAtomicallyFrame;
418 goto retry_pop_stack;
420 // Transaction was not valid: we retry the exception (otherwise continue
421 // with a further call to raiseExceptionHelper)
422 "ptr" trec = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr");
423 StgTSO_trec(CurrentTSO) = trec;
424 R1 = StgAtomicallyFrame_code(Sp);
429 if (frame_type == STOP_FRAME) {
431 * We've stripped the entire stack, the thread is now dead.
432 * We will leave the stack in a GC'able state, see the stg_stop_thread
433 * entry code in StgStartup.cmm.
435 Sp = CurrentTSO + TSO_OFFSET_StgTSO_stack
436 + WDS(TO_W_(StgTSO_stack_size(CurrentTSO))) - WDS(2);
437 Sp(1) = R1; /* save the exception */
438 Sp(0) = stg_enter_info; /* so that GC can traverse this stack */
439 StgTSO_what_next(CurrentTSO) = ThreadKilled::I16;
440 SAVE_THREAD_STATE(); /* inline! */
442 /* The return code goes in BaseReg->rRet, and BaseReg is returned in R1 */
443 StgRegTable_rRet(BaseReg) = ThreadFinished;
449 /* Ok, Sp points to the enclosing CATCH_FRAME or CATCH_STM_FRAME. Pop everything
450 * down to and including this frame, update Su, push R1, and enter the handler.
452 if (frame_type == CATCH_FRAME) {
453 handler = StgCatchFrame_handler(Sp);
455 handler = StgCatchSTMFrame_handler(Sp);
458 /* Restore the blocked/unblocked state for asynchronous exceptions
459 * at the CATCH_FRAME.
461 * If exceptions were unblocked, arrange that they are unblocked
462 * again after executing the handler by pushing an
463 * unblockAsyncExceptions_ret stack frame.
465 * If we've reached an STM catch frame then roll back the nested
466 * transaction we were using.
470 if (frame_type == CATCH_FRAME) {
471 Sp = Sp + SIZEOF_StgCatchFrame;
472 if (StgCatchFrame_exceptions_blocked(frame) == 0) {
474 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
478 trec = StgTSO_trec(CurrentTSO);
479 "ptr" outer = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
480 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
481 foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
482 StgTSO_trec(CurrentTSO) = outer;
483 Sp = Sp + SIZEOF_StgCatchSTMFrame;
486 /* Ensure that async excpetions are blocked when running the handler.
488 StgTSO_flags(CurrentTSO) =
489 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
491 /* Call the handler, passing the exception value and a realworld
492 * token as arguments.
500 jump RET_LBL(stg_ap_pv);
505 /* Args :: R1 :: Exception */