ghc/rts/Exception.hc

   1 /* -----------------------------------------------------------------------------
   2  * $Id: Exception.hc,v 1.28 2003/06/19 10:42:26 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     JMP_(stg_ap_v_ret);
  68   FE_
  69 }
  70
  71 INFO_TABLE_RET( \
  72   stg_unblockAsyncExceptionszh_ret_info, \
  73   stg_unblockAsyncExceptionszh_ret_entry, \
  74   MK_SMALL_BITMAP(0/*framesize*/, 0/*bitmap*/), \
  75   0, 0, 0, RET_SMALL, , EF_, 0, 0 \
  76 );
  77
  78 FN_(stg_unblockAsyncExceptionszh_ret_entry)
  79 {
  80   FB_
  81     ASSERT(CurrentTSO->blocked_exceptions != NULL);
  82 #if defined(GRAN)
  83       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  84                          (StgClosure*)NULL);
  85 #elif defined(PAR)
  86       /* we don't need node info (2nd arg) in this case
  87          (note that CurrentTSO->block_info.closure isn't always set) */
  88       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
  89                          (StgClosure*)NULL);
  90 #else
  91     awakenBlockedQueue(CurrentTSO->blocked_exceptions);
  92 #endif
  93     CurrentTSO->blocked_exceptions = NULL;
  94 #ifdef REG_R1
  95     Sp++;
  96     JMP_(ENTRY_CODE(Sp[0]));
  97 #else
  98     Sp[1] = Sp[0];
  99     Sp++;
 100     JMP_(ENTRY_CODE(Sp[1]));
 101 #endif
 102   FE_
 103 }
 104
 105 FN_(unblockAsyncExceptionszh_fast)
 106 {
 107   FB_
 108     /* Args: R1 :: IO a */
 109     STK_CHK_GEN(2, R1_PTR, unblockAsyncExceptionszh_fast);
 110
 111     if (CurrentTSO->blocked_exceptions != NULL) {
 112 #if defined(GRAN)
 113       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
 114                          CurrentTSO->block_info.closure);
 115 #elif defined(PAR)
 116       // is CurrentTSO->block_info.closure always set to the node
 117       // holding the blocking queue !? -- HWL
 118       awakenBlockedQueue(CurrentTSO->blocked_exceptions,
 119                          CurrentTSO->block_info.closure);
 120 #else
 121       awakenBlockedQueue(CurrentTSO->blocked_exceptions);
 122 #endif
 123       CurrentTSO->blocked_exceptions = NULL;
 124
 125       /* avoid growing the stack unnecessarily */
 126       if (Sp[0] == (W_)&stg_unblockAsyncExceptionszh_ret_info) {
 127         Sp++;
 128       } else {
 129         Sp--;
 130         Sp[0] = (W_)&stg_blockAsyncExceptionszh_ret_info;
 131       }
 132     }
 133     Sp--;
 134     JMP_(stg_ap_v_ret);
 135   FE_
 136 }
 137
 138 INFO_TABLE_RET( \
 139   stg_blockAsyncExceptionszh_ret_info, \
 140   stg_blockAsyncExceptionszh_ret_entry, \
 141   MK_SMALL_BITMAP(0/*framesize*/, 0/*bitmap*/), \
 142   0, 0, 0, RET_SMALL, , EF_, 0, 0 \
 143 );
 144
 145 FN_(stg_blockAsyncExceptionszh_ret_entry)
 146 {
 147   FB_
 148     ASSERT(CurrentTSO->blocked_exceptions == NULL);
 149     CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 150 #ifdef REG_R1
 151     Sp++;
 152     JMP_(ENTRY_CODE(Sp[0]));
 153 #else
 154     Sp[1] = Sp[0];
 155     Sp++;
 156     JMP_(ENTRY_CODE(Sp[1]));
 157 #endif
 158   FE_
 159 }
 160
 161 FN_(killThreadzh_fast)
 162 {
 163   FB_
 164   /* args: R1.p = TSO to kill, R2.p = Exception */
 165
 166   /* This thread may have been relocated.
 167    * (see Schedule.c:threadStackOverflow)
 168    */
 169   while (R1.t->what_next == ThreadRelocated) {
 170     R1.t = R1.t->link;
 171   }
 172
 173   /* If the target thread is currently blocking async exceptions,
 174    * we'll have to block until it's ready to accept them.  The
 175    * exception is interruptible threads - ie. those that are blocked
 176    * on some resource.
 177    */
 178   if (R1.t->blocked_exceptions != NULL && !interruptible(R1.t) ) {
 179
 180     /* ToDo (SMP): locking if destination thread is currently
 181      * running...
 182      */
 183     CurrentTSO->link = R1.t->blocked_exceptions;
 184     R1.t->blocked_exceptions = CurrentTSO;
 185
 186     CurrentTSO->why_blocked = BlockedOnException;
 187     CurrentTSO->block_info.tso = R1.t;
 188
 189     BLOCK( R1_PTR | R2_PTR, killThreadzh_fast );
 190   }
 191
 192   /* Killed threads turn into zombies, which might be garbage
 193    * collected at a later date.  That's why we don't have to
 194    * explicitly remove them from any queues they might be on.
 195    */
 196
 197   /* We might have killed ourselves.  In which case, better be *very*
 198    * careful.  If the exception killed us, then return to the scheduler.
 199    * If the exception went to a catch frame, we'll just continue from
 200    * the handler.
 201    */
 202   if (R1.t == CurrentTSO) {
 203         SaveThreadState();      /* inline! */
 204         STGCALL2(raiseAsyncWithLock, R1.t, R2.cl);
 205         if (CurrentTSO->what_next == ThreadKilled) {
 206                 R1.w = ThreadFinished;
 207                 JMP_(StgReturn);
 208         } else {
 209                 LoadThreadState();
 210                 ASSERT(CurrentTSO->what_next == ThreadRunGHC);
 211                 JMP_(ENTRY_CODE(Sp[0]));
 212         }
 213   } else {
 214         STGCALL2(raiseAsyncWithLock, R1.t, R2.cl);
 215   }
 216
 217   JMP_(ENTRY_CODE(Sp[0]));
 218   FE_
 219 }
 220
 221
 222 /* -----------------------------------------------------------------------------
 223    Catch frames
 224    -------------------------------------------------------------------------- */
 225
 226 #ifdef REG_R1
 227 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 228    FN_(label);                                  \
 229    FN_(label)                                   \
 230    {                                            \
 231       FB_                                       \
 232       Sp += sizeofW(StgCatchFrame);             \
 233       JMP_(ret);                                \
 234       FE_                                       \
 235    }
 236 #else
 237 #define CATCH_FRAME_ENTRY_TEMPLATE(label,ret)   \
 238    FN_(label);                                  \
 239    FN_(label)                                   \
 240    {                                            \
 241       StgWord rval;                             \
 242       FB_                                       \
 243       rval = Sp[0];                             \
 244       Sp++;                                     \
 245       Sp += sizeofW(StgCatchFrame) - 1;         \
 246       Sp[0] = rval;                             \
 247       JMP_(ret);                                \
 248       FE_                                       \
 249    }
 250 #endif
 251
 252 #ifdef REG_R1
 253 #define SP_OFF 0
 254 #else
 255 #define SP_OFF 1
 256 #endif
 257
 258 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_ret,ENTRY_CODE(Sp[SP_OFF]));
 259 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_0_ret,RET_VEC(Sp[SP_OFF],0));
 260 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_1_ret,RET_VEC(Sp[SP_OFF],1));
 261 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_2_ret,RET_VEC(Sp[SP_OFF],2));
 262 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_3_ret,RET_VEC(Sp[SP_OFF],3));
 263 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_4_ret,RET_VEC(Sp[SP_OFF],4));
 264 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_5_ret,RET_VEC(Sp[SP_OFF],5));
 265 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_6_ret,RET_VEC(Sp[SP_OFF],6));
 266 CATCH_FRAME_ENTRY_TEMPLATE(stg_catch_frame_7_ret,RET_VEC(Sp[SP_OFF],7));
 267
 268 #if defined(PROFILING)
 269 #define CATCH_FRAME_BITMAP 7
 270 #define CATCH_FRAME_WORDS  4
 271 #else
 272 #define CATCH_FRAME_BITMAP 1
 273 #define CATCH_FRAME_WORDS  2
 274 #endif
 275
 276 /* Catch frames are very similar to update frames, but when entering
 277  * one we just pop the frame off the stack and perform the correct
 278  * kind of return to the activation record underneath us on the stack.
 279  */
 280
 281 VEC_POLY_INFO_TABLE(stg_catch_frame, \
 282         MK_SMALL_BITMAP(CATCH_FRAME_WORDS, CATCH_FRAME_BITMAP), \
 283         NULL/*srt*/, 0/*srt_off*/, 0/*srt_bitmap*/, CATCH_FRAME,, EF_);
 284
 285 /* -----------------------------------------------------------------------------
 286  * The catch infotable
 287  *
 288  * This should be exactly the same as would be generated by this STG code
 289  *
 290  * catch = {x,h} \n {} -> catch#{x,h}
 291  *
 292  * It is used in deleteThread when reverting blackholes.
 293  * -------------------------------------------------------------------------- */
 294
 295 INFO_TABLE(stg_catch_info,stg_catch_entry,2,0,FUN,,EF_,0,0);
 296 STGFUN(stg_catch_entry)
 297 {
 298   FB_
 299   R2.cl = R1.cl->payload[1]; /* h */
 300   R1.cl = R1.cl->payload[0]; /* x */
 301   JMP_(catchzh_fast);
 302   FE_
 303 }
 304
 305 FN_(catchzh_fast)
 306 {
 307   StgCatchFrame *fp;
 308   FB_
 309
 310     /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
 311     STK_CHK_GEN(sizeofW(StgCatchFrame) + 1, R1_PTR | R2_PTR, catchzh_fast);
 312
 313     /* Set up the catch frame */
 314     Sp -= sizeofW(StgCatchFrame);
 315     fp = (StgCatchFrame *)Sp;
 316     SET_HDR(fp,(StgInfoTable *)&stg_catch_frame_info,CCCS);
 317     fp -> handler = R2.cl;
 318     fp -> exceptions_blocked = (CurrentTSO->blocked_exceptions != NULL);
 319     TICK_CATCHF_PUSHED();
 320
 321
 322 /* Apply R1 to the realworld token */
 323     Sp--;
 324     JMP_(stg_ap_v_ret);
 325   FE_
 326 }
 327
 328 /* -----------------------------------------------------------------------------
 329  * The raise infotable
 330  *
 331  * This should be exactly the same as would be generated by this STG code
 332  *
 333  *   raise = {err} \n {} -> raise#{err}
 334  *
 335  * It is used in raisezh_fast to update thunks on the update list
 336  * -------------------------------------------------------------------------- */
 337
 338 INFO_TABLE(stg_raise_info,stg_raise_entry,1,0,THUNK,,EF_,0,0);
 339 STGFUN(stg_raise_entry)
 340 {
 341   FB_
 342   R1.cl = R1.cl->payload[0];
 343   JMP_(raisezh_fast);
 344   FE_
 345 }
 346
 347 FN_(raisezh_fast)
 348 {
 349   StgClosure *handler;
 350   StgPtr p;
 351   StgClosure *raise_closure;
 352   FB_
 353     /* args : R1.p :: Exception */
 354
 355
 356 #if defined(PROFILING)
 357     /* Debugging tool: on raising an  exception, show where we are. */
 358
 359     /* ToDo: currently this is a hack.  Would be much better if
 360      * the info was only displayed for an *uncaught* exception.
 361      */
 362     if (RtsFlags.ProfFlags.showCCSOnException) {
 363       STGCALL2(fprintCCS,stderr,CCCS);
 364     }
 365 #endif
 366
 367     /* This closure represents the expression 'raise# E' where E
 368      * is the exception raise.  It is used to overwrite all the
 369      * thunks which are currently under evaluataion.
 370      */
 371     /*
 372     // @LDV profiling
 373     // stg_raise_info has THUNK as its closure type. Since a THUNK takes at least
 374     // MIN_UPD_SIZE words in its payload, MIN_UPD_SIZE is more approprate than 1.
 375     // It seems that 1 does not cause any problem unless profiling is performed.
 376     // However, when LDV profiling goes on, we need to linearly scan small object pool,
 377     // where raise_closure is stored, so we should use MIN_UPD_SIZE.
 378     raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
 379                                                sizeofW(StgClosure)+1);
 380      */
 381     raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
 382                                                sizeofW(StgClosure)+MIN_UPD_SIZE);
 383     SET_HDR(raise_closure, &stg_raise_info, CCCS);
 384     raise_closure->payload[0] = R1.cl;
 385
 386     // Walk up the stack, looking for the catch frame.  On the way,
 387     // we update any closures pointed to from update frames with the
 388     // raise closure that we just built.
 389     {
 390         StgPtr next;
 391         StgRetInfoTable *info;
 392
 393         p = Sp;
 394         while(1) {
 395
 396             info = get_ret_itbl((StgClosure *)p);
 397             next = p + stack_frame_sizeW((StgClosure *)p);
 398             switch (info->i.type) {
 399
 400             case UPDATE_FRAME:
 401                 UPD_IND(((StgUpdateFrame *)p)->updatee,raise_closure);
 402                 p = next;
 403                 continue;
 404
 405             case CATCH_FRAME:
 406                 /* found it! */
 407                 break;
 408
 409             case STOP_FRAME:
 410                 /* We've stripped the entire stack, the thread is now dead. */
 411                 Sp = CurrentTSO->stack + CurrentTSO->stack_size - 1;
 412                 Sp[0] = R1.w;           /* save the exception */
 413                 CurrentTSO->what_next = ThreadKilled;
 414                 SaveThreadState();      /* inline! */
 415                 R1.w = ThreadFinished;
 416                 JMP_(StgReturn);
 417
 418             default:
 419                 p = next;
 420                 continue;
 421             }
 422
 423             break;
 424         }
 425     }
 426
 427     /* Ok, p points to the enclosing CATCH_FRAME.  Pop everything down to
 428      * and including this frame, update Su, push R1, and enter the handler.
 429      */
 430     handler = ((StgCatchFrame *)p)->handler;
 431
 432     Sp = (P_)p + sizeofW(StgCatchFrame);
 433
 434     /* Restore the blocked/unblocked state for asynchronous exceptions
 435      * at the CATCH_FRAME.
 436      *
 437      * If exceptions were unblocked, arrange that they are unblocked
 438      * again after executing the handler by pushing an
 439      * unblockAsyncExceptions_ret stack frame.
 440      */
 441     if (! ((StgCatchFrame *)p)->exceptions_blocked) {
 442       *(--Sp) = (W_)&stg_unblockAsyncExceptionszh_ret_info;
 443     }
 444
 445     /* Ensure that async excpetions are blocked when running the handler.
 446     */
 447     if (CurrentTSO->blocked_exceptions == NULL) {
 448       CurrentTSO->blocked_exceptions = END_TSO_QUEUE;
 449     }
 450
 451     /* Call the handler, passing the exception value and a realworld
 452      * token as arguments.
 453      */
 454     Sp -= 2;
 455     Sp[1] = (W_)&stg_ap_v_info;
 456     Sp[0] = R1.w;
 457     R1.cl = handler;
 458     Sp--;
 459     JMP_(stg_ap_p_ret);
 460   FE_
 461 }
 462
 463 FN_(raiseIOzh_fast)
 464 {
 465   FB_
 466   /* Args :: R1.p :: Exception */
 467   JMP_(raisezh_fast);
 468   FE_
 469 }