ghc/rts/Exception.hc

   1 /* -----------------------------------------------------------------------------
   2  * $Id: Exception.hc,v 1.25 2002/04/23 06:34:26 sof Exp $
   3  *
   4  * (c) The GHC Team, 1998-2000
   5  *
   6  * Exception support
   7  *
   8  * ---------------------------------------------------------------------------*/
   9
  10 #include "Stg.h"
  11 #include "Rts.h"
  12 #include "Exception.h"
  13 #include "Schedule.h"
  14 #include "StgRun.h"
  15 #include "Storage.h"
  16 #include "RtsUtils.h"
  17 #include "RtsFlags.h"
  18 #if defined(PAR)
  19 # include "FetchMe.h"
  20 #endif
  21 #if defined(PROFILING)
  22 # include "Profiling.h"
  23 #endif
  24
  25 /* -----------------------------------------------------------------------------
  26    Exception Primitives
  27
  28    A thread can request that asynchronous exceptions not be delivered
  29    ("blocked") for the duration of an I/O computation.  The primitive
  30
  31         blockAsyncExceptions# :: IO a -> IO a
  32
  33    is used for this purpose.  During a blocked section, asynchronous
  34    exceptions may be unblocked again temporarily:
  35
  36         unblockAsyncExceptions# :: IO a -> IO a
  37
  38    Furthermore, asynchronous exceptions are blocked automatically during
  39    the execution of an exception handler.  Both of these primitives
  40    leave a continuation on the stack which reverts to the previous
  41    state (blocked or unblocked) on exit.
  42
  43    A thread which wants to raise an exception in another thread (using
  44    killThread#) must block until the target thread is ready to receive
  45    it.  The action of unblocking exceptions in a thread will release all
  46    the threads waiting to deliver exceptions to that thread.
  47
  48    -------------------------------------------------------------------------- */
  49
  50 FN_(blockAsyncExceptionszh_fast)
  51 {
  52   FB_
  53     /* Args: R1 :: IO a */
  54     STK_CHK_GEN( 2/* worst case */, R1_PTR, blockAsyncExceptionszh_fast, );
  55
  56     if (CurrentTSO->blocked_exceptions == NULL) {
  57       CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
  58       /* avoid growing the stack unnecessarily */
  59       if (Sp[0] == (W_)&stg_blockAsyncExceptionszh_ret_info) {
  60         Sp++;
  61       } else {
  62         Sp--;
  63         Sp[0] = (W_)&stg_unblockAsyncExceptionszh_ret_info;
  64       }
  65     }
  66     Sp--;
  67     Sp[0] = ARG_TAG(0);
  68     JMP_(GET_ENTRY(R1.cl));
  69   FE_
  70 }
  71
  72 INFO_TABLE_SRT_BITMAP(stg_unblockAsyncExceptionszh_ret_info, stg_unblockAsyncExceptionszh_ret_entry, 0, 0, 0, 0, RET_SMALL, , EF_, 0, 0);
  73 FN_(stg_unblockAsyncExceptionszh_ret_entry)
  74 {
  75   FB_
  76     ASSERT(CurrentTSO->blocked_exceptions != NULL);
  77 #if defined(GRAN)
  78       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  79                          (StgClosure*)NULL);
  80 #elif defined(PAR)
  81       /* we don't need node info (2nd arg) in this case
  82          (note that CurrentTSO->block_info.closure isn't always set) */
  83       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  84                          (StgClosure*)NULL);
  85 #else
  86     awakenBlockedQueue(CurrentTSO->blocked_exceptions);
  87 #endif
  88     CurrentTSO->blocked_exceptions = NULL;
  89 #ifdef REG_R1
  90     Sp++;
  91     JMP_(ENTRY_CODE(Sp[0]));
  92 #else
  93     Sp[1] = Sp[0];
  94     Sp++;
  95     JMP_(ENTRY_CODE(Sp[1]));
  96 #endif
  97   FE_
  98 }
  99
 100 FN_(unblockAsyncExceptionszh_fast)
 101 {
 102   FB_
 103     /* Args: R1 :: IO a */
 104     STK_CHK_GEN(2, R1_PTR, unblockAsyncExceptionszh_fast, );
 105
 106     if (CurrentTSO->blocked_exceptions != NULL) {
 107 #if defined(GRAN)
 108       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
 109                          CurrentTSO->block_info.closure);
 110 #elif defined(PAR)
 111       // is CurrentTSO->block_info.closure always set to the node
 112       // holding the blocking queue !? -- HWL
 113       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
 114                          CurrentTSO->block_info.closure);
 115 #else
 116       awakenBlockedQueue(CurrentTSO->blocked_exceptions);
 117 #endif
 118       CurrentTSO->blocked_exceptions = NULL;
 119
 120       /* avoid growing the stack unnecessarily */
 121       if (Sp[0] == (W_)&stg_unblockAsyncExceptionszh_ret_info) {
 122         Sp++;
 123       } else {
 124         Sp--;
 125         Sp[0] = (W_)&stg_blockAsyncExceptionszh_ret_info;
 126       }
 127     }
 128     Sp--;
 129     Sp[0] = ARG_TAG(0);
 130     JMP_(GET_ENTRY(R1.cl));
 131   FE_
 132 }
 133
 134 INFO_TABLE_SRT_BITMAP(stg_blockAsyncExceptionszh_ret_info, stg_blockAsyncExceptionszh_ret_entry, 0, 0, 0, 0, RET_SMALL, , EF_, 0, 0);
 135 FN_(stg_blockAsyncExceptionszh_ret_entry)
 136 {
 137   FB_
 138     ASSERT(CurrentTSO->blocked_exceptions == NULL);
 139     CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 140 #ifdef REG_R1
 141     Sp++;
 142     JMP_(ENTRY_CODE(Sp[0]));
 143 #else
 144     Sp[1] = Sp[0];
 145     Sp++;
 146     JMP_(ENTRY_CODE(Sp[1]));
 147 #endif
 148   FE_
 149 }
 150
 151 FN_(killThreadzh_fast)
 152 {
 153   FB_
 154   /* args: R1.p = TSO to kill, R2.p = Exception */
 155
 156   /* This thread may have been relocated.
 157    * (see Schedule.c:threadStackOverflow)
 158    */
 159   while (R1.t->what_next == ThreadRelocated) {
 160     R1.t = R1.t->link;
 161   }
 162
 163   /* If the target thread is currently blocking async exceptions,
 164    * we'll have to block until it's ready to accept them.  The
 165    * exception is interruptible threads - ie. those that are blocked
 166    * on some resource.
 167    */
 168   if (R1.t->blocked_exceptions != NULL && !interruptible(R1.t) ) {
 169
 170     /* ToDo (SMP): locking if destination thread is currently
 171      * running...
 172      */
 173     CurrentTSO->link = R1.t->blocked_exceptions;
 174     R1.t->blocked_exceptions = CurrentTSO;
 175
 176     CurrentTSO->why_blocked = BlockedOnException;
 177     CurrentTSO->block_info.tso = R1.t;
 178
 179     BLOCK( R1_PTR | R2_PTR, killThreadzh_fast );
 180   }
 181
 182   /* Killed threads turn into zombies, which might be garbage
 183    * collected at a later date.  That's why we don't have to
 184    * explicitly remove them from any queues they might be on.
 185    */
 186
 187   /* We might have killed ourselves.  In which case, better be *very*
 188    * careful.  If the exception killed us, then return to the scheduler.
 189    * If the exception went to a catch frame, we'll just continue from
 190    * the handler.
 191    */
 192   if (R1.t == CurrentTSO) {
 193         SaveThreadState();      /* inline! */
 194         STGCALL2(raiseAsyncWithLock, R1.t, R2.cl);
 195         if (CurrentTSO->what_next == ThreadKilled) {
 196                 R1.w = ThreadFinished;
 197                 JMP_(StgReturn);
 198         }
 199         LoadThreadState();
 200         if (CurrentTSO->what_next == ThreadEnterGHC) {
 201                 R1.w = Sp[0];
 202                 Sp++;
 203                 JMP_(GET_ENTRY(R1.cl));
 204         } else {
 205                 barf("killThreadzh_fast");
 206         }
 207   } else {
 208         STGCALL2(raiseAsyncWithLock, R1.t, R2.cl);
 209   }
 210
 211   JMP_(ENTRY_CODE(Sp[0]));
 212   FE_
 213 }
 214
 215
 216 /* -----------------------------------------------------------------------------
 217    Catch frames
 218    -------------------------------------------------------------------------- */
 219
 220 #ifdef REG_R1
 221 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 222    FN_(label);                                  \
 223    FN_(label)                                   \
 224    {                                            \
 225       FB_                                       \
 226       Su = ((StgCatchFrame *)Sp)->link;         \
 227       Sp += sizeofW(StgCatchFrame);             \
 228       JMP_(ret);                                \
 229       FE_                                       \
 230    }
 231 #else
 232 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 233    FN_(label);                                  \
 234    FN_(label)                                   \
 235    {                                            \
 236       StgWord rval;                             \
 237       FB_                                       \
 238       rval = Sp[0];                             \
 239       Sp++;                                     \
 240       Su = ((StgCatchFrame *)Sp)->link;         \
 241       Sp += sizeofW(StgCatchFrame) - 1;         \
 242       Sp[0] = rval;                             \
 243       JMP_(ret);                                \
 244       FE_                                       \
 245    }
 246 #endif
 247
 248 #ifdef REG_R1
 249 #define SP_OFF 0
 250 #else
 251 #define SP_OFF 1
 252 #endif
 253
 254 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_entry,ENTRY_CODE(Sp[SP_OFF]));
 255 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_0_entry,RET_VEC(Sp[SP_OFF],0));
 256 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_1_entry,RET_VEC(Sp[SP_OFF],1));
 257 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_2_entry,RET_VEC(Sp[SP_OFF],2));
 258 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_3_entry,RET_VEC(Sp[SP_OFF],3));
 259 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_4_entry,RET_VEC(Sp[SP_OFF],4));
 260 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_5_entry,RET_VEC(Sp[SP_OFF],5));
 261 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_6_entry,RET_VEC(Sp[SP_OFF],6));
 262 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_7_entry,RET_VEC(Sp[SP_OFF],7));
 263
 264 #if defined(PROFILING)
 265 #define CATCH_FRAME_BITMAP 15
 266 #else
 267 #define CATCH_FRAME_BITMAP 3
 268 #endif
 269
 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.
 273  */
 274
 275 VEC_POLY_INFO_TABLE(stg_catch_frame, CATCH_FRAME_BITMAP, NULL/*srt*/, 0/*srt_off*/, 0/*srt_len*/, CATCH_FRAME,, EF_);
 276
 277 /* -----------------------------------------------------------------------------
 278  * The catch infotable
 279  *
 280  * This should be exactly the same as would be generated by this STG code
 281  *
 282  * catch = {x,h} \n {} -> catch#{x,h}
 283  *
 284  * It is used in deleteThread when reverting blackholes.
 285  * -------------------------------------------------------------------------- */
 286
 287 INFO_TABLE(stg_catch_info,stg_catch_entry,2,0,FUN,,EF_,0,0);
 288 STGFUN(stg_catch_entry)
 289 {
 290   FB_
 291   R2.cl = R1.cl->payload[1]; /* h */
 292   R1.cl = R1.cl->payload[0]; /* x */
 293   JMP_(catchzh_fast);
 294   FE_
 295 }
 296
 297 FN_(catchzh_fast)
 298 {
 299   StgCatchFrame *fp;
 300   FB_
 301
 302     /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
 303     STK_CHK_GEN(sizeofW(StgCatchFrame) + 1, R1_PTR | R2_PTR, catchzh_fast, );
 304
 305     /* Set up the catch frame */
 306     Sp -= sizeofW(StgCatchFrame);
 307     fp = (StgCatchFrame *)Sp;
 308     SET_HDR(fp,(StgInfoTable *)&stg_catch_frame_info,CCCS);
 309     fp -> handler = R2.cl;
 310     fp -> exceptions_blocked = (CurrentTSO->blocked_exceptions != NULL);
 311     fp -> link = Su;
 312     Su = (StgUpdateFrame *)fp;
 313     TICK_CATCHF_PUSHED();
 314
 315     /* Push realworld token and enter R1. */
 316     Sp--;
 317     Sp[0] = ARG_TAG(0);
 318     TICK_ENT_VIA_NODE();
 319     JMP_(GET_ENTRY(R1.cl));
 320
 321   FE_
 322 }
 323
 324 /* -----------------------------------------------------------------------------
 325  * The raise infotable
 326  *
 327  * This should be exactly the same as would be generated by this STG code
 328  *
 329  *   raise = {err} \n {} -> raise#{err}
 330  *
 331  * It is used in raisezh_fast to update thunks on the update list
 332  * -------------------------------------------------------------------------- */
 333
 334 INFO_TABLE(stg_raise_info,stg_raise_entry,1,0,THUNK,,EF_,0,0);
 335 STGFUN(stg_raise_entry)
 336 {
 337   FB_
 338   R1.cl = R1.cl->payload[0];
 339   JMP_(raisezh_fast);
 340   FE_
 341 }
 342
 343 FN_(raisezh_fast)
 344 {
 345   StgClosure *handler;
 346   StgUpdateFrame *p;
 347   StgClosure *raise_closure;
 348   FB_
 349     /* args : R1 = exception */
 350
 351
 352 #if defined(PROFILING)
 353     /* Debugging tool: on raising an  exception, show where we are. */
 354
 355     /* ToDo: currently this is a hack.  Would be much better if
 356      * the info was only displayed for an *uncaught* exception.
 357      */
 358     if (RtsFlags.ProfFlags.showCCSOnException) {
 359       STGCALL2(fprintCCS,stderr,CCCS);
 360     }
 361 #endif
 362
 363     p = Su;
 364
 365     /* This closure represents the expression 'raise# E' where E
 366      * is the exception raise.  It is used to overwrite all the
 367      * thunks which are currently under evaluataion.
 368      */
 369     /*
 370     // @LDV profiling
 371     // stg_raise_info has THUNK as its closure type. Since a THUNK takes at least
 372     // MIN_UPD_SIZE words in its payload, MIN_UPD_SIZE is more approprate than 1.
 373     // It seems that 1 does not cause any problem unless profiling is performed.
 374     // However, when LDV profiling goes on, we need to linearly scan small object pool,
 375     // where raise_closure is stored, so we should use MIN_UPD_SIZE.
 376     raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
 377                                                sizeofW(StgClosure)+1);
 378      */
 379     raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
 380                                                sizeofW(StgClosure)+MIN_UPD_SIZE);
 381     SET_HDR(raise_closure, &stg_raise_info, CCCS);
 382     raise_closure->payload[0] = R1.cl;
 383
 384     while (1) {
 385
 386       switch (get_itbl(p)->type) {
 387
 388       case UPDATE_FRAME:
 389         UPD_IND(p->updatee,raise_closure);
 390         p = p->link;
 391         continue;
 392
 393       case SEQ_FRAME:
 394         p = ((StgSeqFrame *)p)->link;
 395         continue;
 396
 397       case CATCH_FRAME:
 398         /* found it! */
 399         break;
 400
 401       case STOP_FRAME:
 402         /* We've stripped the entire stack, the thread is now dead. */
 403         Sp = CurrentTSO->stack + CurrentTSO->stack_size - 1;
 404         Sp[0] = R1.w;           /* save the exception */
 405         Su = (StgUpdateFrame *)(Sp+1);
 406         CurrentTSO->what_next = ThreadKilled;
 407         SaveThreadState();      /* inline! */
 408         R1.w = ThreadFinished;
 409         JMP_(StgReturn);
 410
 411       default:
 412         barf("raisezh_fast: weird activation record");
 413       }
 414
 415       break;
 416
 417     }
 418
 419     /* Ok, p points to the enclosing CATCH_FRAME.  Pop everything down to
 420      * and including this frame, update Su, push R1, and enter the handler.
 421      */
 422     Su = ((StgCatchFrame *)p)->link;
 423     handler = ((StgCatchFrame *)p)->handler;
 424
 425     Sp = (P_)p + sizeofW(StgCatchFrame);
 426
 427     /* Restore the blocked/unblocked state for asynchronous exceptions
 428      * at the CATCH_FRAME.
 429      *
 430      * If exceptions were unblocked, arrange that they are unblocked
 431      * again after executing the handler by pushing an
 432      * unblockAsyncExceptions_ret stack frame.
 433      */
 434     if (! ((StgCatchFrame *)p)->exceptions_blocked) {
 435       *(--Sp) = (W_)&stg_unblockAsyncExceptionszh_ret_info;
 436     }
 437
 438     /* Ensure that async excpetions are blocked when running the handler.
 439     */
 440     if (CurrentTSO->blocked_exceptions == NULL) {
 441       CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 442     }
 443
 444     /* Enter the handler, passing the exception value and a realworld
 445      * token as arguments.
 446      */
 447     Sp -= 2;
 448     Sp[0] = R1.w;
 449     Sp[1] = ARG_TAG(0);
 450     TICK_ENT_VIA_NODE();
 451     R1.cl = handler;
 452     JMP_(GET_ENTRY(R1.cl));
 453
 454   FE_
 455 }