ghc/rts/Exception.hc

   1 /* -----------------------------------------------------------------------------
   2  * $Id: Exception.hc,v 1.8 2000/02/24 17:20:46 simonmar Exp $
   3  *
   4  * (c) The GHC Team, 1998-1999
   5  *
   6  * Exception support
   7  *
   8  * ---------------------------------------------------------------------------*/
   9
  10 #include "Rts.h"
  11 #include "Exception.h"
  12 #include "Schedule.h"
  13 #include "StgRun.h"
  14 #include "Storage.h"
  15 #include "RtsUtils.h"
  16 #include "RtsFlags.h"
  17 #if defined(PAR)
  18 # include "FetchMe.h"
  19 #endif
  20
  21 /* -----------------------------------------------------------------------------
  22    Exception Primitives
  23
  24    A thread can request that asynchronous exceptions not be delivered
  25    ("blocked") for the duration of an I/O computation.  The primitive
  26
  27         blockAsyncExceptions# :: IO a -> IO a
  28
  29    is used for this purpose.  During a blocked section, asynchronous
  30    exceptions may be unblocked again temporarily:
  31
  32         unblockAsyncExceptions# :: IO a -> IO a
  33
  34    Furthermore, asynchronous exceptions are blocked automatically during
  35    the execution of an exception handler.  Both of these primitives
  36    leave a continuation on the stack which reverts to the previous
  37    state (blocked or unblocked) on exit.
  38
  39    A thread which wants to raise an exception in another thread (using
  40    killThread#) must block until the target thread is ready to receive
  41    it.  The action of unblocking exceptions in a thread will release all
  42    the threads waiting to deliver exceptions to that thread.
  43
  44    -------------------------------------------------------------------------- */
  45
  46 FN_(blockAsyncExceptionszh_fast)
  47 {
  48   FB_
  49     /* Args: R1 :: IO a */
  50     STK_CHK_GEN( 2/* worst case */, R1_PTR, blockAsyncExceptionszh_fast, );
  51
  52     if (CurrentTSO->blocked_exceptions == NULL) {
  53       CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
  54       /* avoid growing the stack unnecessarily */
  55       if (Sp[0] == (W_)&blockAsyncExceptionszh_ret_info) {
  56         Sp++;
  57       } else {
  58         Sp--;
  59         Sp[0] = (W_)&unblockAsyncExceptionszh_ret_info;
  60       }
  61     }
  62     Sp--;
  63     Sp[0] = ARG_TAG(0);
  64     JMP_(GET_ENTRY(R1.cl));
  65   FE_
  66 }
  67
  68 INFO_TABLE_SRT_BITMAP(unblockAsyncExceptionszh_ret_info, unblockAsyncExceptionszh_ret_entry, 0, 0, 0, 0, RET_SMALL, , EF_, 0, 0);
  69 FN_(unblockAsyncExceptionszh_ret_entry)
  70 {
  71   FB_
  72     ASSERT(CurrentTSO->blocked_exceptions != NULL);
  73 #if defined(GRAN)
  74       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  75                          CurrentTSO->block_info.closure);
  76 #elif defined(PAR)
  77       // is CurrentTSO->block_info.closure always set to the node
  78       // holding the blocking queue !? -- HWL
  79       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  80                          CurrentTSO->block_info.closure);
  81 #else
  82     awakenBlockedQueue(CurrentTSO->blocked_exceptions);
  83 #endif
  84     CurrentTSO->blocked_exceptions = NULL;
  85 #ifdef REG_R1
  86     Sp++;
  87     JMP_(ENTRY_CODE(Sp[0]));
  88 #else
  89     Sp[1] = Sp[0];
  90     Sp++;
  91     JMP_(ENTRY_CODE(Sp[1]));
  92 #endif
  93   FE_
  94 }
  95
  96 FN_(unblockAsyncExceptionszh_fast)
  97 {
  98   FB_
  99     /* Args: R1 :: IO a */
 100     STK_CHK_GEN(2, R1_PTR, unblockAsyncExceptionszh_fast, );
 101
 102     if (CurrentTSO->blocked_exceptions != NULL) {
 103 #if defined(GRAN)
 104       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
 105                          CurrentTSO->block_info.closure);
 106 #elif defined(PAR)
 107       // is CurrentTSO->block_info.closure always set to the node
 108       // holding the blocking queue !? -- HWL
 109       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
 110                          CurrentTSO->block_info.closure);
 111 #else
 112       awakenBlockedQueue(CurrentTSO->blocked_exceptions);
 113 #endif
 114       CurrentTSO->blocked_exceptions = NULL;
 115
 116       /* avoid growing the stack unnecessarily */
 117       if (Sp[0] == (W_)&unblockAsyncExceptionszh_ret_info) {
 118         Sp++;
 119       } else {
 120         Sp--;
 121         Sp[0] = (W_)&blockAsyncExceptionszh_ret_info;
 122       }
 123     }
 124     Sp--;
 125     Sp[0] = ARG_TAG(0);
 126     JMP_(GET_ENTRY(R1.cl));
 127   FE_
 128 }
 129
 130 INFO_TABLE_SRT_BITMAP(blockAsyncExceptionszh_ret_info, blockAsyncExceptionszh_ret_entry, 0, 0, 0, 0, RET_SMALL, , EF_, 0, 0);
 131 FN_(blockAsyncExceptionszh_ret_entry)
 132 {
 133   FB_
 134     ASSERT(CurrentTSO->blocked_exceptions == NULL);
 135     CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 136 #ifdef REG_R1
 137     Sp++;
 138     JMP_(ENTRY_CODE(Sp[0]));
 139 #else
 140     Sp[1] = Sp[0];
 141     Sp++;
 142     JMP_(ENTRY_CODE(Sp[1]));
 143 #endif
 144   FE_
 145 }
 146
 147
 148 FN_(killThreadzh_fast)
 149 {
 150   FB_
 151   /* args: R1.p = TSO to kill, R2.p = Exception */
 152
 153   /* This thread may have been relocated.
 154    * (see Schedule.c:threadStackOverflow)
 155    */
 156   while (R1.t->whatNext == ThreadRelocated) {
 157     R1.t = R1.t->link;
 158   }
 159
 160   /* If the target thread is currently blocking async exceptions,
 161    * we'll have to block until it's ready to accept them.
 162    */
 163   if (R1.t->blocked_exceptions != NULL) {
 164
 165         /* ToDo (SMP): locking if destination thread is currently
 166          * running...
 167          */
 168         CurrentTSO->link = R1.t->blocked_exceptions;
 169         R1.t->blocked_exceptions = CurrentTSO;
 170
 171         CurrentTSO->why_blocked = BlockedOnException;
 172         CurrentTSO->block_info.tso = R1.t;
 173
 174         BLOCK( R1_PTR | R2_PTR, killThreadzh_fast );
 175   }
 176
 177   /* Killed threads turn into zombies, which might be garbage
 178    * collected at a later date.  That's why we don't have to
 179    * explicitly remove them from any queues they might be on.
 180    */
 181
 182   /* We might have killed ourselves.  In which case, better be *very*
 183    * careful.  If the exception killed us, then return to the scheduler.
 184    * If the exception went to a catch frame, we'll just continue from
 185    * the handler.
 186    */
 187   if (R1.t == CurrentTSO) {
 188         SaveThreadState();      /* inline! */
 189         STGCALL2(raiseAsync, R1.t, R2.cl);
 190         if (CurrentTSO->whatNext == ThreadKilled) {
 191                 R1.w = ThreadYielding;
 192                 JMP_(StgReturn);
 193         }
 194         LoadThreadState();
 195         if (CurrentTSO->whatNext == ThreadEnterGHC) {
 196                 R1.w = Sp[0];
 197                 Sp++;
 198                 JMP_(GET_ENTRY(R1.cl));
 199         } else {
 200                 barf("killThreadzh_fast");
 201         }
 202   } else {
 203         STGCALL2(raiseAsync, R1.t, R2.cl);
 204   }
 205
 206   JMP_(ENTRY_CODE(Sp[0]));
 207   FE_
 208 }
 209
 210 /* -----------------------------------------------------------------------------
 211    Catch frames
 212    -------------------------------------------------------------------------- */
 213
 214 #ifdef REG_R1
 215 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 216    FN_(label);                                  \
 217    FN_(label)                                   \
 218    {                                            \
 219       FB_                                       \
 220       Su = ((StgCatchFrame *)Sp)->link;         \
 221       Sp += sizeofW(StgCatchFrame);             \
 222       JMP_(ret);                                \
 223       FE_                                       \
 224    }
 225 #else
 226 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 227    FN_(label);                                  \
 228    FN_(label)                                   \
 229    {                                            \
 230       StgWord rval;                             \
 231       FB_                                       \
 232       rval = Sp[0];                             \
 233       Sp++;                                     \
 234       Su = ((StgCatchFrame *)Sp)->link;         \
 235       Sp += sizeofW(StgCatchFrame) - 1;         \
 236       Sp[0] = rval;                             \
 237       JMP_(ret);                                \
 238       FE_                                       \
 239    }
 240 #endif
 241
 242 #ifdef REG_R1
 243 #define SP_OFF 0
 244 #else
 245 #define SP_OFF 1
 246 #endif
 247
 248 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_entry,ENTRY_CODE(Sp[SP_OFF]));
 249 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_0_entry,RET_VEC(Sp[SP_OFF],0));
 250 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_1_entry,RET_VEC(Sp[SP_OFF],1));
 251 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_2_entry,RET_VEC(Sp[SP_OFF],2));
 252 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_3_entry,RET_VEC(Sp[SP_OFF],3));
 253 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_4_entry,RET_VEC(Sp[SP_OFF],4));
 254 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_5_entry,RET_VEC(Sp[SP_OFF],5));
 255 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_6_entry,RET_VEC(Sp[SP_OFF],6));
 256 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_7_entry,RET_VEC(Sp[SP_OFF],7));
 257
 258 #ifdef PROFILING
 259 #define CATCH_FRAME_BITMAP 7
 260 #else
 261 #define CATCH_FRAME_BITMAP 3
 262 #endif
 263
 264 /* Catch frames are very similar to update frames, but when entering
 265  * one we just pop the frame off the stack and perform the correct
 266  * kind of return to the activation record underneath us on the stack.
 267  */
 268
 269 VEC_POLY_INFO_TABLE(catch_frame, CATCH_FRAME_BITMAP, NULL/*srt*/, 0/*srt_off*/, 0/*srt_len*/, CATCH_FRAME,, EF_);
 270
 271 /* -----------------------------------------------------------------------------
 272  * The catch infotable
 273  *
 274  * This should be exactly the same as would be generated by this STG code
 275  *
 276  * catch = {x,h} \n {} -> catch#{x,h}
 277  *
 278  * It is used in deleteThread when reverting blackholes.
 279  * -------------------------------------------------------------------------- */
 280
 281 INFO_TABLE(catch_info,catch_entry,2,0,FUN,,EF_,0,0);
 282 STGFUN(catch_entry)
 283 {
 284   FB_
 285   R2.cl = payloadCPtr(R1.cl,1); /* h */
 286   R1.cl = payloadCPtr(R1.cl,0); /* x */
 287   JMP_(catchzh_fast);
 288   FE_
 289 }
 290
 291 FN_(catchzh_fast)
 292 {
 293   StgCatchFrame *fp;
 294   FB_
 295
 296     /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
 297     STK_CHK_GEN(sizeofW(StgCatchFrame) + 1, R1_PTR | R2_PTR, catchzh_fast, );
 298
 299     /* Set up the catch frame */
 300     Sp -= sizeofW(StgCatchFrame);
 301     fp = (StgCatchFrame *)Sp;
 302     SET_HDR(fp,(StgInfoTable *)&catch_frame_info,CCCS);
 303     fp -> handler = R2.cl;
 304     fp -> exceptions_blocked = (CurrentTSO->blocked_exceptions != NULL);
 305     fp -> link = Su;
 306     Su = (StgUpdateFrame *)fp;
 307     TICK_CATCHF_PUSHED();
 308
 309     /* Push realworld token and enter R1. */
 310     Sp--;
 311     Sp[0] = ARG_TAG(0);
 312     TICK_ENT_VIA_NODE();
 313     JMP_(GET_ENTRY(R1.cl));
 314
 315   FE_
 316 }
 317
 318 /* -----------------------------------------------------------------------------
 319  * The raise infotable
 320  *
 321  * This should be exactly the same as would be generated by this STG code
 322  *
 323  *   raise = {err} \n {} -> raise#{err}
 324  *
 325  * It is used in raisezh_fast to update thunks on the update list
 326  * -------------------------------------------------------------------------- */
 327
 328 INFO_TABLE(raise_info,raise_entry,1,0,FUN,,EF_,0,0);
 329 STGFUN(raise_entry)
 330 {
 331   FB_
 332   R1.cl = R1.cl->payload[0];
 333   JMP_(raisezh_fast);
 334   FE_
 335 }
 336
 337 FN_(raisezh_fast)
 338 {
 339   StgClosure *handler;
 340   StgUpdateFrame *p;
 341   StgClosure *raise_closure;
 342   FB_
 343     /* args : R1 = error */
 344
 345
 346 #if defined(PROFILING)
 347
 348     /* Debugging tool: on raising an  exception, show where we are. */
 349
 350     /* ToDo: currently this is a hack.  Would be much better if
 351      * the info was only displayed for an *uncaught* exception.
 352      */
 353     if (RtsFlags.ProfFlags.showCCSOnException) {
 354       STGCALL2(print_ccs,stderr,CCCS);
 355     }
 356
 357 #endif
 358
 359     p = Su;
 360
 361     /* This closure represents the expression 'raise# E' where E
 362      * is the exception raise.  It is used to overwrite all the
 363      * thunks which are currently under evaluataion.
 364      */
 365     raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
 366                                                sizeofW(StgClosure)+1);
 367     raise_closure->header.info = &raise_info;
 368     raise_closure->payload[0] = R1.cl;
 369
 370     while (1) {
 371
 372       switch (get_itbl(p)->type) {
 373
 374       case UPDATE_FRAME:
 375         UPD_IND(p->updatee,raise_closure);
 376         p = p->link;
 377         continue;
 378
 379       case SEQ_FRAME:
 380         p = ((StgSeqFrame *)p)->link;
 381         continue;
 382
 383       case CATCH_FRAME:
 384         /* found it! */
 385         break;
 386
 387       case STOP_FRAME:
 388         barf("raisezh_fast: STOP_FRAME");
 389
 390       default:
 391         barf("raisezh_fast: weird activation record");
 392       }
 393
 394       break;
 395
 396     }
 397
 398     /* Ok, p points to the enclosing CATCH_FRAME.  Pop everything down to
 399      * and including this frame, update Su, push R1, and enter the handler.
 400      */
 401     Su = ((StgCatchFrame *)p)->link;
 402     handler = ((StgCatchFrame *)p)->handler;
 403
 404     Sp = (P_)p + sizeofW(StgCatchFrame);
 405
 406     /* Restore the blocked/unblocked state for asynchronous exceptions
 407      * at the CATCH_FRAME.
 408      *
 409      * If exceptions were unblocked, arrange that they are unblocked
 410      * again after executing the handler by pushing an
 411      * unblockAsyncExceptions_ret stack frame.
 412      */
 413     if (! ((StgCatchFrame *)p)->exceptions_blocked) {
 414       *(--Sp) = (W_)&unblockAsyncExceptionszh_ret_info;
 415     }
 416
 417     /* Ensure that async excpetions are blocked when running the handler.
 418     */
 419     if (CurrentTSO->blocked_exceptions == NULL) {
 420       CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 421     }
 422
 423     /* Enter the handler, passing the exception value and a realworld
 424      * token as arguments.
 425      */
 426     Sp -= 2;
 427     Sp[0] = R1.w;
 428     Sp[1] = ARG_TAG(0);
 429     TICK_ENT_VIA_NODE();
 430     R1.cl = handler;
 431     JMP_(GET_ENTRY(R1.cl));
 432
 433   FE_
 434 }