ghc/rts/Exception.hc

   1 /* -----------------------------------------------------------------------------
   2  * $Id: Exception.hc,v 1.3 2000/01/13 14:34:02 hwloidl 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       Sp--;
  55       Sp[0] = (W_)&unblockAsyncExceptionszh_ret_info;
  56     }
  57     Sp--;
  58     Sp[0] = ARG_TAG(0);
  59     JMP_(GET_ENTRY(R1.cl));
  60   FE_
  61 }
  62
  63 INFO_TABLE_SRT_BITMAP(unblockAsyncExceptionszh_ret_info, unblockAsyncExceptionszh_ret_entry, 0, 0, 0, 0, RET_SMALL, , EF_, 0, 0);
  64 FN_(unblockAsyncExceptionszh_ret_entry)
  65 {
  66   FB_
  67     ASSERT(CurrentTSO->blocked_exceptions != NULL);
  68 #if defined(GRAN)
  69 # error FixME
  70 #elif defined(PAR)
  71       // is CurrentTSO->block_info.closure always set to the node
  72       // holding the blocking queue !? -- HWL
  73       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  74                          CurrentTSO->block_info.closure);
  75 #else
  76     awakenBlockedQueue(CurrentTSO->blocked_exceptions);
  77 #endif
  78     CurrentTSO->blocked_exceptions = NULL;
  79     Sp++;
  80     JMP_(ENTRY_CODE(Sp[0]));
  81   FE_
  82 }
  83
  84 FN_(unblockAsyncExceptionszh_fast)
  85 {
  86   FB_
  87     /* Args: R1 :: IO a */
  88     STK_CHK_GEN(2, R1_PTR, unblockAsyncExceptionszh_fast, );
  89
  90     if (CurrentTSO->blocked_exceptions != NULL) {
  91 #if defined(GRAN)
  92 # error FixME
  93 #elif defined(PAR)
  94       // is CurrentTSO->block_info.closure always set to the node
  95       // holding the blocking queue !? -- HWL
  96       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  97                          CurrentTSO->block_info.closure);
  98 #else
  99       awakenBlockedQueue(CurrentTSO->blocked_exceptions);
 100 #endif
 101       CurrentTSO->blocked_exceptions = NULL;
 102       Sp--;
 103       Sp[0] = (W_)&blockAsyncExceptionszh_ret_info;
 104     }
 105     Sp--;
 106     Sp[0] = ARG_TAG(0);
 107     JMP_(GET_ENTRY(R1.cl));
 108   FE_
 109 }
 110
 111 INFO_TABLE_SRT_BITMAP(blockAsyncExceptionszh_ret_info, blockAsyncExceptionszh_ret_entry, 0, 0, 0, 0, RET_SMALL, , EF_, 0, 0);
 112 FN_(blockAsyncExceptionszh_ret_entry)
 113 {
 114   FB_
 115     ASSERT(CurrentTSO->blocked_exceptions == NULL);
 116     CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 117     Sp++;
 118     JMP_(ENTRY_CODE(Sp[0]));
 119   FE_
 120 }
 121
 122
 123 FN_(killThreadzh_fast)
 124 {
 125   FB_
 126   /* args: R1.p = TSO to kill, R2.p = Exception */
 127
 128   /* If the target thread is currently blocking async exceptions,
 129    * we'll have to block until it's ready to accept them.
 130    */
 131   if (R1.t->blocked_exceptions != NULL) {
 132
 133         /* ToDo (SMP): locking if destination thread is currently
 134          * running...
 135          */
 136         CurrentTSO->link = R1.t->blocked_exceptions;
 137         R1.t->blocked_exceptions = CurrentTSO;
 138
 139         CurrentTSO->why_blocked = BlockedOnException;
 140         CurrentTSO->block_info.tso = R1.t;
 141
 142         BLOCK( R1_PTR | R2_PTR, killThreadzh_fast );
 143   }
 144
 145   /* Killed threads turn into zombies, which might be garbage
 146    * collected at a later date.  That's why we don't have to
 147    * explicitly remove them from any queues they might be on.
 148    */
 149
 150   /* We might have killed ourselves.  In which case, better be *very*
 151    * careful.  If the exception killed us, then return to the scheduler.
 152    * If the exception went to a catch frame, we'll just continue from
 153    * the handler.
 154    */
 155   if (R1.t == CurrentTSO) {
 156         SaveThreadState();      /* inline! */
 157         STGCALL2(raiseAsync, R1.t, R2.cl);
 158         if (CurrentTSO->whatNext == ThreadKilled) {
 159                 R1.w = ThreadYielding;
 160                 JMP_(StgReturn);
 161         }
 162         LoadThreadState();
 163         if (CurrentTSO->whatNext == ThreadEnterGHC) {
 164                 R1.w = Sp[0];
 165                 Sp++;
 166                 JMP_(GET_ENTRY(R1.cl));
 167         } else {
 168                 barf("killThreadzh_fast");
 169         }
 170   } else {
 171         STGCALL2(raiseAsync, R1.t, R2.cl);
 172   }
 173
 174   JMP_(ENTRY_CODE(Sp[0]));
 175   FE_
 176 }
 177
 178 /* -----------------------------------------------------------------------------
 179    Catch frames
 180    -------------------------------------------------------------------------- */
 181
 182 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 183    FN_(label);                                  \
 184    FN_(label)                                   \
 185    {                                            \
 186       FB_                                       \
 187       Su = ((StgCatchFrame *)Sp)->link;         \
 188       Sp += sizeofW(StgCatchFrame);             \
 189       JMP_(ret);                                \
 190       FE_                                       \
 191    }
 192
 193 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_entry,ENTRY_CODE(Sp[0]));
 194 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_0_entry,RET_VEC(Sp[0],0));
 195 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_1_entry,RET_VEC(Sp[0],1));
 196 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_2_entry,RET_VEC(Sp[0],2));
 197 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_3_entry,RET_VEC(Sp[0],3));
 198 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_4_entry,RET_VEC(Sp[0],4));
 199 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_5_entry,RET_VEC(Sp[0],5));
 200 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_6_entry,RET_VEC(Sp[0],6));
 201 CATCH_FRAME_ENTRY_TEMPLATE(catch_frame_7_entry,RET_VEC(Sp[0],7));
 202
 203 #ifdef PROFILING
 204 #define CATCH_FRAME_BITMAP 7
 205 #else
 206 #define CATCH_FRAME_BITMAP 3
 207 #endif
 208
 209 /* Catch frames are very similar to update frames, but when entering
 210  * one we just pop the frame off the stack and perform the correct
 211  * kind of return to the activation record underneath us on the stack.
 212  */
 213
 214 VEC_POLY_INFO_TABLE(catch_frame, CATCH_FRAME_BITMAP, NULL/*srt*/, 0/*srt_off*/, 0/*srt_len*/, CATCH_FRAME,, EF_);
 215
 216 /* -----------------------------------------------------------------------------
 217  * The catch infotable
 218  *
 219  * This should be exactly the same as would be generated by this STG code
 220  *
 221  * catch = {x,h} \n {} -> catch#{x,h}
 222  *
 223  * It is used in deleteThread when reverting blackholes.
 224  * -------------------------------------------------------------------------- */
 225
 226 INFO_TABLE(catch_info,catch_entry,2,0,FUN,,EF_,0,0);
 227 STGFUN(catch_entry)
 228 {
 229   FB_
 230   R2.cl = payloadCPtr(R1.cl,1); /* h */
 231   R1.cl = payloadCPtr(R1.cl,0); /* x */
 232   JMP_(catchzh_fast);
 233   FE_
 234 }
 235
 236 FN_(catchzh_fast)
 237 {
 238   StgCatchFrame *fp;
 239   FB_
 240
 241     /* args: R1 = m, R2 = handler */
 242     STK_CHK_GEN(sizeofW(StgCatchFrame), R1_PTR | R2_PTR, catchzh_fast, );
 243     Sp -= sizeofW(StgCatchFrame);
 244     fp = (StgCatchFrame *)Sp;
 245     SET_HDR(fp,(StgInfoTable *)&catch_frame_info,CCCS);
 246     fp -> handler = R2.cl;
 247     fp -> exceptions_blocked = (CurrentTSO->blocked_exceptions != NULL);
 248     fp -> link = Su;
 249     Su = (StgUpdateFrame *)fp;
 250     TICK_CATCHF_PUSHED();
 251     TICK_ENT_VIA_NODE();
 252     JMP_(GET_ENTRY(R1.cl));
 253
 254   FE_
 255 }
 256
 257 /* -----------------------------------------------------------------------------
 258  * The raise infotable
 259  *
 260  * This should be exactly the same as would be generated by this STG code
 261  *
 262  *   raise = {err} \n {} -> raise#{err}
 263  *
 264  * It is used in raisezh_fast to update thunks on the update list
 265  * -------------------------------------------------------------------------- */
 266
 267 INFO_TABLE(raise_info,raise_entry,1,0,FUN,,EF_,0,0);
 268 STGFUN(raise_entry)
 269 {
 270   FB_
 271   R1.cl = R1.cl->payload[0];
 272   JMP_(raisezh_fast);
 273   FE_
 274 }
 275
 276 FN_(raisezh_fast)
 277 {
 278   StgClosure *handler;
 279   StgUpdateFrame *p;
 280   StgClosure *raise_closure;
 281   FB_
 282     /* args : R1 = error */
 283
 284
 285 #if defined(PROFILING)
 286
 287     /* Debugging tool: on raising an  exception, show where we are. */
 288
 289     /* ToDo: currently this is a hack.  Would be much better if
 290      * the info was only displayed for an *uncaught* exception.
 291      */
 292     if (RtsFlags.ProfFlags.showCCSOnException) {
 293       STGCALL2(print_ccs,stderr,CCCS);
 294     }
 295
 296 #endif
 297
 298     p = Su;
 299
 300     /* This closure represents the expression 'raise# E' where E
 301      * is the exception raise.  It is used to overwrite all the
 302      * thunks which are currently under evaluataion.
 303      */
 304     raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
 305                                                sizeofW(StgClosure)+1);
 306     raise_closure->header.info = &raise_info;
 307     raise_closure->payload[0] = R1.cl;
 308
 309     while (1) {
 310
 311       switch (get_itbl(p)->type) {
 312
 313       case UPDATE_FRAME:
 314         UPD_IND(p->updatee,raise_closure);
 315         p = p->link;
 316         continue;
 317
 318       case SEQ_FRAME:
 319         p = ((StgSeqFrame *)p)->link;
 320         continue;
 321
 322       case CATCH_FRAME:
 323         /* found it! */
 324         break;
 325
 326       case STOP_FRAME:
 327         barf("raisezh_fast: STOP_FRAME");
 328
 329       default:
 330         barf("raisezh_fast: weird activation record");
 331       }
 332
 333       break;
 334
 335     }
 336
 337     /* Ok, p points to the enclosing CATCH_FRAME.  Pop everything down to
 338      * and including this frame, update Su, push R1, and enter the handler.
 339      */
 340     Su = ((StgCatchFrame *)p)->link;
 341     handler = ((StgCatchFrame *)p)->handler;
 342
 343     Sp = (P_)p + sizeofW(StgCatchFrame) - 1;
 344
 345     /* Restore the blocked/unblocked state for asynchronous exceptions
 346      * at the CATCH_FRAME.
 347      *
 348      * If exceptions were unblocked, arrange that they are unblocked
 349      * again after executing the handler by pushing an
 350      * unblockAsyncExceptions_ret stack frame.
 351      */
 352     if (! ((StgCatchFrame *)p)->exceptions_blocked) {
 353       *(Sp--) = (W_)&unblockAsyncExceptionszh_ret_info;
 354     }
 355
 356     /* Ensure that async excpetions are blocked when running the handler.
 357     */
 358     if (CurrentTSO->blocked_exceptions == NULL) {
 359       CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 360     }
 361
 362     /* Enter the handler, passing the exception value as an argument.
 363      */
 364     *Sp = R1.w;
 365     TICK_ENT_VIA_NODE();
 366     R1.cl = handler;
 367     JMP_(GET_ENTRY(R1.cl));
 368
 369   FE_
 370 }