ghc/rts/Exception.hc

   1 /* -----------------------------------------------------------------------------
   2  * $Id: Exception.hc,v 1.20 2001/03/23 16:36:21 simonmar 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(raiseAsync, 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(raiseAsync, R1.t, R2.cl);
 209   }
 210
 211   JMP_(ENTRY_CODE(Sp[0]));
 212   FE_
 213 }
 214
 215 /* -----------------------------------------------------------------------------
 216    Catch frames
 217    -------------------------------------------------------------------------- */
 218
 219 #ifdef REG_R1
 220 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 221    FN_(label);                                  \
 222    FN_(label)                                   \
 223    {                                            \
 224       FB_                                       \
 225       Su = ((StgCatchFrame *)Sp)->link;         \
 226       Sp += sizeofW(StgCatchFrame);             \
 227       JMP_(ret);                                \
 228       FE_                                       \
 229    }
 230 #else
 231 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 232    FN_(label);                                  \
 233    FN_(label)                                   \
 234    {                                            \
 235       StgWord rval;                             \
 236       FB_                                       \
 237       rval = Sp[0];                             \
 238       Sp++;                                     \
 239       Su = ((StgCatchFrame *)Sp)->link;         \
 240       Sp += sizeofW(StgCatchFrame) - 1;         \
 241       Sp[0] = rval;                             \
 242       JMP_(ret);                                \
 243       FE_                                       \
 244    }
 245 #endif
 246
 247 #ifdef REG_R1
 248 #define SP_OFF 0
 249 #else
 250 #define SP_OFF 1
 251 #endif
 252
 253 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_entry,ENTRY_CODE(Sp[SP_OFF]));
 254 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_0_entry,RET_VEC(Sp[SP_OFF],0));
 255 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_1_entry,RET_VEC(Sp[SP_OFF],1));
 256 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_2_entry,RET_VEC(Sp[SP_OFF],2));
 257 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_3_entry,RET_VEC(Sp[SP_OFF],3));
 258 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_4_entry,RET_VEC(Sp[SP_OFF],4));
 259 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_5_entry,RET_VEC(Sp[SP_OFF],5));
 260 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_6_entry,RET_VEC(Sp[SP_OFF],6));
 261 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_7_entry,RET_VEC(Sp[SP_OFF],7));
 262
 263 #ifdef PROFILING
 264 #define CATCH_FRAME_BITMAP 7
 265 #else
 266 #define CATCH_FRAME_BITMAP 3
 267 #endif
 268
 269 /* Catch frames are very similar to update frames, but when entering
 270  * one we just pop the frame off the stack and perform the correct
 271  * kind of return to the activation record underneath us on the stack.
 272  */
 273
 274 VEC_POLY_INFO_TABLE(stg_catch_frame, CATCH_FRAME_BITMAP, NULL/*srt*/, 0/*srt_off*/, 0/*srt_len*/, CATCH_FRAME,, EF_);
 275
 276 /* -----------------------------------------------------------------------------
 277  * The catch infotable
 278  *
 279  * This should be exactly the same as would be generated by this STG code
 280  *
 281  * catch = {x,h} \n {} -> catch#{x,h}
 282  *
 283  * It is used in deleteThread when reverting blackholes.
 284  * -------------------------------------------------------------------------- */
 285
 286 INFO_TABLE(stg_catch_info,stg_catch_entry,2,0,FUN,,EF_,0,0);
 287 STGFUN(stg_catch_entry)
 288 {
 289   FB_
 290   R2.cl = R1.cl->payload[1]; /* h */
 291   R1.cl = R1.cl->payload[0]; /* x */
 292   JMP_(catchzh_fast);
 293   FE_
 294 }
 295
 296 FN_(catchzh_fast)
 297 {
 298   StgCatchFrame *fp;
 299   FB_
 300
 301     /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
 302     STK_CHK_GEN(sizeofW(StgCatchFrame) + 1, R1_PTR | R2_PTR, catchzh_fast, );
 303
 304     /* Set up the catch frame */
 305     Sp -= sizeofW(StgCatchFrame);
 306     fp = (StgCatchFrame *)Sp;
 307     SET_HDR(fp,(StgInfoTable *)&stg_catch_frame_info,CCCS);
 308     fp -> handler = R2.cl;
 309     fp -> exceptions_blocked = (CurrentTSO->blocked_exceptions != NULL);
 310     fp -> link = Su;
 311     Su = (StgUpdateFrame *)fp;
 312     TICK_CATCHF_PUSHED();
 313
 314     /* Push realworld token and enter R1. */
 315     Sp--;
 316     Sp[0] = ARG_TAG(0);
 317     TICK_ENT_VIA_NODE();
 318     JMP_(GET_ENTRY(R1.cl));
 319
 320   FE_
 321 }
 322
 323 /* -----------------------------------------------------------------------------
 324  * The raise infotable
 325  *
 326  * This should be exactly the same as would be generated by this STG code
 327  *
 328  *   raise = {err} \n {} -> raise#{err}
 329  *
 330  * It is used in raisezh_fast to update thunks on the update list
 331  * -------------------------------------------------------------------------- */
 332
 333 INFO_TABLE(stg_raise_info,stg_raise_entry,1,0,THUNK,,EF_,0,0);
 334 STGFUN(stg_raise_entry)
 335 {
 336   FB_
 337   R1.cl = R1.cl->payload[0];
 338   JMP_(raisezh_fast);
 339   FE_
 340 }
 341
 342 FN_(raisezh_fast)
 343 {
 344   StgClosure *handler;
 345   StgUpdateFrame *p;
 346   StgClosure *raise_closure;
 347   FB_
 348     /* args : R1 = exception */
 349
 350
 351 #if defined(PROFILING)
 352
 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(print_ccs,stderr,CCCS);
 360     }
 361
 362 #endif
 363
 364     p = Su;
 365
 366     /* This closure represents the expression 'raise# E' where E
 367      * is the exception raise.  It is used to overwrite all the
 368      * thunks which are currently under evaluataion.
 369      */
 370     raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
 371                                                sizeofW(StgClosure)+1);
 372     raise_closure->header.info = &stg_raise_info;
 373     raise_closure->payload[0] = R1.cl;
 374
 375     while (1) {
 376
 377       switch (get_itbl(p)->type) {
 378
 379       case UPDATE_FRAME:
 380         UPD_IND(p->updatee,raise_closure);
 381         p = p->link;
 382         continue;
 383
 384       case SEQ_FRAME:
 385         p = ((StgSeqFrame *)p)->link;
 386         continue;
 387
 388       case CATCH_FRAME:
 389         /* found it! */
 390         break;
 391
 392       case STOP_FRAME:
 393         /* We've stripped the entire stack, the thread is now dead. */
 394         Sp = CurrentTSO->stack + CurrentTSO->stack_size - 1;
 395         Sp[0] = R1.w;           /* save the exception */
 396         Su = (StgUpdateFrame *)(Sp+1);
 397         CurrentTSO->what_next = ThreadKilled;
 398         SaveThreadState();      /* inline! */
 399         R1.w = ThreadFinished;
 400         JMP_(StgReturn);
 401
 402       default:
 403         barf("raisezh_fast: weird activation record");
 404       }
 405
 406       break;
 407
 408     }
 409
 410     /* Ok, p points to the enclosing CATCH_FRAME.  Pop everything down to
 411      * and including this frame, update Su, push R1, and enter the handler.
 412      */
 413     Su = ((StgCatchFrame *)p)->link;
 414     handler = ((StgCatchFrame *)p)->handler;
 415
 416     Sp = (P_)p + sizeofW(StgCatchFrame);
 417
 418     /* Restore the blocked/unblocked state for asynchronous exceptions
 419      * at the CATCH_FRAME.
 420      *
 421      * If exceptions were unblocked, arrange that they are unblocked
 422      * again after executing the handler by pushing an
 423      * unblockAsyncExceptions_ret stack frame.
 424      */
 425     if (! ((StgCatchFrame *)p)->exceptions_blocked) {
 426       *(--Sp) = (W_)&stg_unblockAsyncExceptionszh_ret_info;
 427     }
 428
 429     /* Ensure that async excpetions are blocked when running the handler.
 430     */
 431     if (CurrentTSO->blocked_exceptions == NULL) {
 432       CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 433     }
 434
 435     /* Enter the handler, passing the exception value and a realworld
 436      * token as arguments.
 437      */
 438     Sp -= 2;
 439     Sp[0] = R1.w;
 440     Sp[1] = ARG_TAG(0);
 441     TICK_ENT_VIA_NODE();
 442     R1.cl = handler;
 443     JMP_(GET_ENTRY(R1.cl));
 444
 445   FE_
 446 }