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 )
56 // Not true: see comments above
57 // ASSERT(StgTSO_blocked_exceptions(CurrentTSO) != NULL);
59 foreign "C" awakenBlockedExceptionQueue(MyCapability() "ptr",
60 CurrentTSO "ptr") [R1];
62 StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) &
63 ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
67 jump %ENTRY_CODE(Sp(0));
71 jump %ENTRY_CODE(Sp(1));
75 INFO_TABLE_RET( stg_blockAsyncExceptionszh_ret,
76 0/*framesize*/, 0/*bitmap*/, RET_SMALL )
78 // Not true: see comments above
79 // ASSERT(StgTSO_blocked_exceptions(CurrentTSO) == NULL);
81 StgTSO_flags(CurrentTSO) =
82 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
86 jump %ENTRY_CODE(Sp(0));
90 jump %ENTRY_CODE(Sp(1));
94 blockAsyncExceptionszh_fast
96 /* Args: R1 :: IO a */
97 STK_CHK_GEN( WDS(2)/* worst case */, R1_PTR, blockAsyncExceptionszh_fast);
99 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
101 StgTSO_flags(CurrentTSO) =
102 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
104 /* avoid growing the stack unnecessarily */
105 if (Sp(0) == stg_blockAsyncExceptionszh_ret_info) {
109 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
117 unblockAsyncExceptionszh_fast
119 /* Args: R1 :: IO a */
120 STK_CHK_GEN( WDS(2), R1_PTR, unblockAsyncExceptionszh_fast);
122 if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {
123 foreign "C" awakenBlockedExceptionQueue(MyCapability() "ptr",
124 CurrentTSO "ptr") [R1];
126 StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) &
127 ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
129 /* avoid growing the stack unnecessarily */
130 if (Sp(0) == stg_unblockAsyncExceptionszh_ret_info) {
134 Sp(0) = stg_blockAsyncExceptionszh_ret_info;
145 /* args: R1 = TSO to kill, R2 = Exception */
154 STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, killThreadzh_fast);
157 * We might have killed ourselves. In which case, better be *very*
158 * careful. If the exception killed us, then return to the scheduler.
159 * If the exception went to a catch frame, we'll just continue from
162 if (target == CurrentTSO) {
164 /* ToDo: what if the current thread is blocking exceptions? */
165 foreign "C" throwToSingleThreaded(MyCapability() "ptr",
166 target "ptr", exception "ptr")[R1,R2];
167 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
172 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
173 jump %ENTRY_CODE(Sp(0));
178 out = BaseReg + OFFSET_StgRegTable_rmp_tmp_w;
180 retcode = foreign "C" throwTo(MyCapability() "ptr",
186 switch [THROWTO_SUCCESS .. THROWTO_BLOCKED] (retcode) {
188 case THROWTO_SUCCESS: {
189 jump %ENTRY_CODE(Sp(0));
192 case THROWTO_BLOCKED: {
194 // we must block, and call throwToReleaseTarget() before returning
195 jump stg_block_throwto;
201 /* -----------------------------------------------------------------------------
203 -------------------------------------------------------------------------- */
206 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret) \
209 Sp = Sp + SIZEOF_StgCatchFrame; \
213 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret) \
218 Sp = Sp + SIZEOF_StgCatchFrame; \
230 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_0_ret,%RET_VEC(Sp(SP_OFF),0))
231 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_1_ret,%RET_VEC(Sp(SP_OFF),1))
232 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_2_ret,%RET_VEC(Sp(SP_OFF),2))
233 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_3_ret,%RET_VEC(Sp(SP_OFF),3))
234 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_4_ret,%RET_VEC(Sp(SP_OFF),4))
235 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_5_ret,%RET_VEC(Sp(SP_OFF),5))
236 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_6_ret,%RET_VEC(Sp(SP_OFF),6))
237 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_7_ret,%RET_VEC(Sp(SP_OFF),7))
239 #if MAX_VECTORED_RTN > 8
240 #error MAX_VECTORED_RTN has changed: please modify stg_catch_frame too.
243 #if defined(PROFILING)
244 #define CATCH_FRAME_BITMAP 7
245 #define CATCH_FRAME_WORDS 4
247 #define CATCH_FRAME_BITMAP 1
248 #define CATCH_FRAME_WORDS 2
251 /* Catch frames are very similar to update frames, but when entering
252 * one we just pop the frame off the stack and perform the correct
253 * kind of return to the activation record underneath us on the stack.
256 INFO_TABLE_RET(stg_catch_frame,
257 CATCH_FRAME_WORDS, CATCH_FRAME_BITMAP,
259 stg_catch_frame_0_ret,
260 stg_catch_frame_1_ret,
261 stg_catch_frame_2_ret,
262 stg_catch_frame_3_ret,
263 stg_catch_frame_4_ret,
264 stg_catch_frame_5_ret,
265 stg_catch_frame_6_ret,
266 stg_catch_frame_7_ret)
267 CATCH_FRAME_ENTRY_TEMPLATE(,%ENTRY_CODE(Sp(SP_OFF)))
269 /* -----------------------------------------------------------------------------
270 * The catch infotable
272 * This should be exactly the same as would be generated by this STG code
274 * catch = {x,h} \n {} -> catch#{x,h}
276 * It is used in deleteThread when reverting blackholes.
277 * -------------------------------------------------------------------------- */
279 INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
281 R2 = StgClosure_payload(R1,1); /* h */
282 R1 = StgClosure_payload(R1,0); /* x */
288 /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
289 STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, catchzh_fast);
291 /* Set up the catch frame */
292 Sp = Sp - SIZEOF_StgCatchFrame;
293 SET_HDR(Sp,stg_catch_frame_info,W_[CCCS]);
295 StgCatchFrame_handler(Sp) = R2;
296 StgCatchFrame_exceptions_blocked(Sp) = TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX;
297 TICK_CATCHF_PUSHED();
299 /* Apply R1 to the realworld token */
305 /* -----------------------------------------------------------------------------
306 * The raise infotable
308 * This should be exactly the same as would be generated by this STG code
310 * raise = {err} \n {} -> raise#{err}
312 * It is used in raisezh_fast to update thunks on the update list
313 * -------------------------------------------------------------------------- */
315 INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
317 R1 = StgThunk_payload(R1,0);
326 /* args : R1 :: Exception */
329 #if defined(PROFILING)
330 /* Debugging tool: on raising an exception, show where we are. */
332 /* ToDo: currently this is a hack. Would be much better if
333 * the info was only displayed for an *uncaught* exception.
335 if (RtsFlags_ProfFlags_showCCSOnException(RtsFlags) != 0::I32) {
336 foreign "C" fprintCCS_stderr(W_[CCCS] "ptr");
341 StgTSO_sp(CurrentTSO) = Sp;
342 frame_type = foreign "C" raiseExceptionHelper(BaseReg "ptr", CurrentTSO "ptr", R1 "ptr");
343 Sp = StgTSO_sp(CurrentTSO);
344 if (frame_type == ATOMICALLY_FRAME) {
345 /* The exception has reached the edge of a memory transaction. Check that
346 * the transaction is valid. If not then perhaps the exception should
347 * not have been thrown: re-run the transaction */
350 trec = StgTSO_trec(CurrentTSO);
351 r = foreign "C" stmValidateNestOfTransactions(trec "ptr");
352 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr");
353 StgTSO_trec(CurrentTSO) = NO_TREC;
355 // Transaction was valid: continue searching for a catch frame
356 Sp = Sp + SIZEOF_StgAtomicallyFrame;
357 goto retry_pop_stack;
359 // Transaction was not valid: we retry the exception (otherwise continue
360 // with a further call to raiseExceptionHelper)
361 "ptr" trec = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr");
362 StgTSO_trec(CurrentTSO) = trec;
363 R1 = StgAtomicallyFrame_code(Sp);
368 if (frame_type == STOP_FRAME) {
370 * We've stripped the entire stack, the thread is now dead.
371 * We will leave the stack in a GC'able state, see the stg_stop_thread
372 * entry code in StgStartup.cmm.
374 Sp = CurrentTSO + TSO_OFFSET_StgTSO_stack
375 + WDS(TO_W_(StgTSO_stack_size(CurrentTSO))) - WDS(2);
376 Sp(1) = R1; /* save the exception */
377 Sp(0) = stg_enter_info; /* so that GC can traverse this stack */
378 StgTSO_what_next(CurrentTSO) = ThreadKilled::I16;
379 SAVE_THREAD_STATE(); /* inline! */
381 /* The return code goes in BaseReg->rRet, and BaseReg is returned in R1 */
382 StgRegTable_rRet(BaseReg) = ThreadFinished;
388 /* Ok, Sp points to the enclosing CATCH_FRAME or CATCH_STM_FRAME. Pop everything
389 * down to and including this frame, update Su, push R1, and enter the handler.
391 if (frame_type == CATCH_FRAME) {
392 handler = StgCatchFrame_handler(Sp);
394 handler = StgCatchSTMFrame_handler(Sp);
397 /* Restore the blocked/unblocked state for asynchronous exceptions
398 * at the CATCH_FRAME.
400 * If exceptions were unblocked, arrange that they are unblocked
401 * again after executing the handler by pushing an
402 * unblockAsyncExceptions_ret stack frame.
406 if (frame_type == CATCH_FRAME) {
407 Sp = Sp + SIZEOF_StgCatchFrame;
408 if (StgCatchFrame_exceptions_blocked(frame) == 0) {
410 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
413 Sp = Sp + SIZEOF_StgCatchSTMFrame;
416 /* Ensure that async excpetions are blocked when running the handler.
418 StgTSO_flags(CurrentTSO) =
419 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
421 /* Call the handler, passing the exception value and a realworld
422 * token as arguments.
430 jump RET_LBL(stg_ap_pv);
435 /* Args :: R1 :: Exception */