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 /* avoid growing the stack unnecessarily */
127 if (Sp(0) == stg_unblockAsyncExceptionszh_ret_info) {
131 Sp(0) = stg_blockAsyncExceptionszh_ret_info;
142 /* args: R1 = TSO to kill, R2 = Exception */
151 STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, killThreadzh_fast);
154 * We might have killed ourselves. In which case, better be *very*
155 * careful. If the exception killed us, then return to the scheduler.
156 * If the exception went to a catch frame, we'll just continue from
159 if (target == CurrentTSO) {
161 /* ToDo: what if the current thread is blocking exceptions? */
162 foreign "C" throwToSingleThreaded(MyCapability() "ptr",
163 target "ptr", exception "ptr")[R1,R2];
164 if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
169 ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
170 jump %ENTRY_CODE(Sp(0));
175 out = BaseReg + OFFSET_StgRegTable_rmp_tmp_w;
177 retcode = foreign "C" throwTo(MyCapability() "ptr",
183 switch [THROWTO_SUCCESS .. THROWTO_BLOCKED] (retcode) {
185 case THROWTO_SUCCESS: {
186 jump %ENTRY_CODE(Sp(0));
189 case THROWTO_BLOCKED: {
191 // we must block, and call throwToReleaseTarget() before returning
192 jump stg_block_throwto;
198 /* -----------------------------------------------------------------------------
200 -------------------------------------------------------------------------- */
203 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret) \
206 Sp = Sp + SIZEOF_StgCatchFrame; \
210 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret) \
215 Sp = Sp + SIZEOF_StgCatchFrame; \
227 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_0_ret,%RET_VEC(Sp(SP_OFF),0))
228 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_1_ret,%RET_VEC(Sp(SP_OFF),1))
229 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_2_ret,%RET_VEC(Sp(SP_OFF),2))
230 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_3_ret,%RET_VEC(Sp(SP_OFF),3))
231 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_4_ret,%RET_VEC(Sp(SP_OFF),4))
232 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_5_ret,%RET_VEC(Sp(SP_OFF),5))
233 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_6_ret,%RET_VEC(Sp(SP_OFF),6))
234 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_7_ret,%RET_VEC(Sp(SP_OFF),7))
236 #if MAX_VECTORED_RTN > 8
237 #error MAX_VECTORED_RTN has changed: please modify stg_catch_frame too.
240 #if defined(PROFILING)
241 #define CATCH_FRAME_BITMAP 7
242 #define CATCH_FRAME_WORDS 4
244 #define CATCH_FRAME_BITMAP 1
245 #define CATCH_FRAME_WORDS 2
248 /* Catch frames are very similar to update frames, but when entering
249 * one we just pop the frame off the stack and perform the correct
250 * kind of return to the activation record underneath us on the stack.
253 INFO_TABLE_RET(stg_catch_frame,
254 CATCH_FRAME_WORDS, CATCH_FRAME_BITMAP,
256 stg_catch_frame_0_ret,
257 stg_catch_frame_1_ret,
258 stg_catch_frame_2_ret,
259 stg_catch_frame_3_ret,
260 stg_catch_frame_4_ret,
261 stg_catch_frame_5_ret,
262 stg_catch_frame_6_ret,
263 stg_catch_frame_7_ret)
264 CATCH_FRAME_ENTRY_TEMPLATE(,%ENTRY_CODE(Sp(SP_OFF)))
266 /* -----------------------------------------------------------------------------
267 * The catch infotable
269 * This should be exactly the same as would be generated by this STG code
271 * catch = {x,h} \n {} -> catch#{x,h}
273 * It is used in deleteThread when reverting blackholes.
274 * -------------------------------------------------------------------------- */
276 INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
278 R2 = StgClosure_payload(R1,1); /* h */
279 R1 = StgClosure_payload(R1,0); /* x */
285 /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
286 STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, catchzh_fast);
288 /* Set up the catch frame */
289 Sp = Sp - SIZEOF_StgCatchFrame;
290 SET_HDR(Sp,stg_catch_frame_info,W_[CCCS]);
292 StgCatchFrame_handler(Sp) = R2;
293 StgCatchFrame_exceptions_blocked(Sp) = TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX;
294 TICK_CATCHF_PUSHED();
296 /* Apply R1 to the realworld token */
302 /* -----------------------------------------------------------------------------
303 * The raise infotable
305 * This should be exactly the same as would be generated by this STG code
307 * raise = {err} \n {} -> raise#{err}
309 * It is used in raisezh_fast to update thunks on the update list
310 * -------------------------------------------------------------------------- */
312 INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
314 R1 = StgThunk_payload(R1,0);
323 /* args : R1 :: Exception */
326 #if defined(PROFILING)
327 /* Debugging tool: on raising an exception, show where we are. */
329 /* ToDo: currently this is a hack. Would be much better if
330 * the info was only displayed for an *uncaught* exception.
332 if (RtsFlags_ProfFlags_showCCSOnException(RtsFlags) != 0::I32) {
333 foreign "C" fprintCCS_stderr(W_[CCCS] "ptr");
338 StgTSO_sp(CurrentTSO) = Sp;
339 frame_type = foreign "C" raiseExceptionHelper(BaseReg "ptr", CurrentTSO "ptr", R1 "ptr");
340 Sp = StgTSO_sp(CurrentTSO);
341 if (frame_type == ATOMICALLY_FRAME) {
342 /* The exception has reached the edge of a memory transaction. Check that
343 * the transaction is valid. If not then perhaps the exception should
344 * not have been thrown: re-run the transaction */
347 trec = StgTSO_trec(CurrentTSO);
348 r = foreign "C" stmValidateNestOfTransactions(trec "ptr");
349 foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr");
350 StgTSO_trec(CurrentTSO) = NO_TREC;
352 // Transaction was valid: continue searching for a catch frame
353 Sp = Sp + SIZEOF_StgAtomicallyFrame;
354 goto retry_pop_stack;
356 // Transaction was not valid: we retry the exception (otherwise continue
357 // with a further call to raiseExceptionHelper)
358 "ptr" trec = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr");
359 StgTSO_trec(CurrentTSO) = trec;
360 R1 = StgAtomicallyFrame_code(Sp);
365 if (frame_type == STOP_FRAME) {
367 * We've stripped the entire stack, the thread is now dead.
368 * We will leave the stack in a GC'able state, see the stg_stop_thread
369 * entry code in StgStartup.cmm.
371 Sp = CurrentTSO + TSO_OFFSET_StgTSO_stack
372 + WDS(TO_W_(StgTSO_stack_size(CurrentTSO))) - WDS(2);
373 Sp(1) = R1; /* save the exception */
374 Sp(0) = stg_enter_info; /* so that GC can traverse this stack */
375 StgTSO_what_next(CurrentTSO) = ThreadKilled::I16;
376 SAVE_THREAD_STATE(); /* inline! */
378 /* The return code goes in BaseReg->rRet, and BaseReg is returned in R1 */
379 StgRegTable_rRet(BaseReg) = ThreadFinished;
385 /* Ok, Sp points to the enclosing CATCH_FRAME or CATCH_STM_FRAME. Pop everything
386 * down to and including this frame, update Su, push R1, and enter the handler.
388 if (frame_type == CATCH_FRAME) {
389 handler = StgCatchFrame_handler(Sp);
391 handler = StgCatchSTMFrame_handler(Sp);
394 /* Restore the blocked/unblocked state for asynchronous exceptions
395 * at the CATCH_FRAME.
397 * If exceptions were unblocked, arrange that they are unblocked
398 * again after executing the handler by pushing an
399 * unblockAsyncExceptions_ret stack frame.
403 if (frame_type == CATCH_FRAME) {
404 Sp = Sp + SIZEOF_StgCatchFrame;
405 if (StgCatchFrame_exceptions_blocked(frame) == 0) {
407 Sp(0) = stg_unblockAsyncExceptionszh_ret_info;
410 Sp = Sp + SIZEOF_StgCatchSTMFrame;
413 /* Ensure that async excpetions are blocked when running the handler.
415 StgTSO_flags(CurrentTSO) =
416 StgTSO_flags(CurrentTSO) | TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32;
418 /* Call the handler, passing the exception value and a realworld
419 * token as arguments.
427 jump RET_LBL(stg_ap_pv);
432 /* Args :: R1 :: Exception */