rts/win32/AsyncIO.c

   1 /* AsyncIO.c
   2  *
   3  * Integrating Win32 asynchronous I/O with the GHC RTS.
   4  *
   5  * (c) sof, 2002-2003.
   6  */
   7
   8 #if !defined(THREADED_RTS)
   9
  10 #include "Rts.h"
  11 #include "RtsUtils.h"
  12 #include <windows.h>
  13 #include <stdio.h>
  14 #include "Schedule.h"
  15 #include "RtsFlags.h"
  16 #include "Capability.h"
  17 #include "win32/AsyncIO.h"
  18 #include "win32/IOManager.h"
  19
  20 /*
  21  * Overview:
  22  *
  23  * Haskell code issue asynchronous I/O requests via the
  24  * async{Read,Write,DoOp}# primops. These cause addIORequest()
  25  * to be invoked, which forwards the request to the underlying
  26  * asynchronous I/O subsystem. Each request is tagged with a unique
  27  * ID.
  28  *
  29  * addIORequest() returns this ID, so that when the blocked CH
  30  * thread is added onto blocked_queue, its TSO is annotated with
  31  * it. Upon completion of an I/O request, the async I/O handling
  32  * code makes a back-call to signal its completion; the local
  33  * onIOComplete() routine. It adds the IO request ID (along with
  34  * its result data) to a queue of completed requests before returning.
  35  *
  36  * The queue of completed IO request is read by the thread operating
  37  * the RTS scheduler. It de-queues the CH threads corresponding
  38  * to the request IDs, making them runnable again.
  39  *
  40  */
  41
  42 typedef struct CompletedReq {
  43     unsigned int   reqID;
  44     int            len;
  45     int            errCode;
  46 } CompletedReq;
  47
  48 #define MAX_REQUESTS 200
  49
  50 static CRITICAL_SECTION queue_lock;
  51 static HANDLE           completed_req_event = INVALID_HANDLE_VALUE;
  52 static HANDLE           abandon_req_wait = INVALID_HANDLE_VALUE;
  53 static HANDLE           wait_handles[2];
  54 static CompletedReq     completedTable[MAX_REQUESTS];
  55 static int              completed_hw;
  56 static HANDLE           completed_table_sema;
  57 static int              issued_reqs;
  58
  59 static void
  60 onIOComplete(unsigned int reqID,
  61              int   fd STG_UNUSED,
  62              int   len,
  63              void* buf STG_UNUSED,
  64              int   errCode)
  65 {
  66     DWORD dwRes;
  67     /* Deposit result of request in queue/table..when there's room. */
  68     dwRes = WaitForSingleObject(completed_table_sema, INFINITE);
  69     switch (dwRes) {
  70     case WAIT_OBJECT_0:
  71         break;
  72     default:
  73         /* Not likely */
  74         fprintf(stderr, "onIOComplete: failed to grab table semaphore, dropping request 0x%x\n", reqID);
  75         fflush(stderr);
  76         return;
  77     }
  78     EnterCriticalSection(&queue_lock);
  79     if (completed_hw == MAX_REQUESTS) {
  80         /* Shouldn't happen */
  81         fprintf(stderr, "onIOComplete: ERROR -- Request table overflow (%d); dropping.\n", reqID);
  82         fflush(stderr);
  83     } else {
  84 #if 0
  85         fprintf(stderr, "onCompl: %d %d %d %d %d\n",
  86                 reqID, len, errCode, issued_reqs, completed_hw);
  87         fflush(stderr);
  88 #endif
  89         completedTable[completed_hw].reqID   = reqID;
  90         completedTable[completed_hw].len     = len;
  91         completedTable[completed_hw].errCode = errCode;
  92         completed_hw++;
  93         issued_reqs--;
  94         if (completed_hw == 1) {
  95             /* The event is used to wake up the scheduler thread should it
  96              * be blocked waiting for requests to complete. The event resets once
  97              * that thread has cleared out the request queue/table.
  98              */
  99             SetEvent(completed_req_event);
 100         }
 101     }
 102     LeaveCriticalSection(&queue_lock);
 103 }
 104
 105 unsigned int
 106 addIORequest(int   fd,
 107              int   forWriting,
 108              int   isSock,
 109              int   len,
 110              char* buf)
 111 {
 112     EnterCriticalSection(&queue_lock);
 113     issued_reqs++;
 114     LeaveCriticalSection(&queue_lock);
 115 #if 0
 116     fprintf(stderr, "addIOReq: %d %d %d\n", fd, forWriting, len); fflush(stderr);
 117 #endif
 118     return AddIORequest(fd,forWriting,isSock,len,buf,onIOComplete);
 119 }
 120
 121 unsigned int
 122 addDelayRequest(int msecs)
 123 {
 124     EnterCriticalSection(&queue_lock);
 125     issued_reqs++;
 126     LeaveCriticalSection(&queue_lock);
 127 #if 0
 128     fprintf(stderr, "addDelayReq: %d\n", msecs); fflush(stderr);
 129 #endif
 130     return AddDelayRequest(msecs,onIOComplete);
 131 }
 132
 133 unsigned int
 134 addDoProcRequest(void* proc, void* param)
 135 {
 136     EnterCriticalSection(&queue_lock);
 137     issued_reqs++;
 138     LeaveCriticalSection(&queue_lock);
 139 #if 0
 140     fprintf(stderr, "addProcReq: %p %p\n", proc, param); fflush(stderr);
 141 #endif
 142     return AddProcRequest(proc,param,onIOComplete);
 143 }
 144
 145
 146 int
 147 startupAsyncIO()
 148 {
 149     if (!StartIOManager()) {
 150         return 0;
 151     }
 152     InitializeCriticalSection(&queue_lock);
 153     /* Create a pair of events:
 154      *
 155      *    - completed_req_event  -- signals the deposit of request result; manual reset.
 156      *    - abandon_req_wait     -- external OS thread tells current RTS/Scheduler
 157      *                              thread to abandon wait for IO request completion.
 158      *                              Auto reset.
 159      */
 160     completed_req_event = CreateEvent (NULL, TRUE,  FALSE, NULL);
 161     abandon_req_wait    = CreateEvent (NULL, FALSE, FALSE, NULL);
 162     wait_handles[0] = completed_req_event;
 163     wait_handles[1] = abandon_req_wait;
 164     completed_hw = 0;
 165     if ( !(completed_table_sema = CreateSemaphore (NULL, MAX_REQUESTS, MAX_REQUESTS, NULL)) ) {
 166         DWORD rc = GetLastError();
 167         fprintf(stderr, "startupAsyncIO: CreateSemaphore failed 0x%x\n", (int)rc);
 168         fflush(stderr);
 169     }
 170
 171     return ( completed_req_event  != INVALID_HANDLE_VALUE &&
 172              abandon_req_wait     != INVALID_HANDLE_VALUE &&
 173              completed_table_sema != NULL );
 174 }
 175
 176 void
 177 shutdownAsyncIO()
 178 {
 179     ShutdownIOManager();
 180     if (completed_req_event != INVALID_HANDLE_VALUE) {
 181         CloseHandle(completed_req_event);
 182         completed_req_event = INVALID_HANDLE_VALUE;
 183     }
 184     if (abandon_req_wait != INVALID_HANDLE_VALUE) {
 185         CloseHandle(abandon_req_wait);
 186         abandon_req_wait = INVALID_HANDLE_VALUE;
 187     }
 188     if (completed_table_sema != NULL) {
 189         CloseHandle(completed_table_sema);
 190         completed_table_sema = NULL;
 191     }
 192 }
 193
 194 /*
 195  * Function: awaitRequests(wait)
 196  *
 197  * Check for the completion of external IO work requests. Worker
 198  * threads signal completion of IO requests by depositing them
 199  * in a table (completedTable). awaitRequests() matches up
 200  * requests in that table with threads on the blocked_queue,
 201  * making the threads whose IO requests have completed runnable
 202  * again.
 203  *
 204  * awaitRequests() is called by the scheduler periodically _or_ if
 205  * it is out of work, and need to wait for the completion of IO
 206  * requests to make further progress. In the latter scenario,
 207  * awaitRequests() will simply block waiting for worker threads
 208  * to complete if the 'completedTable' is empty.
 209  */
 210 int
 211 awaitRequests(rtsBool wait)
 212 {
 213 #ifndef THREADED_RTS
 214   // none of this is actually used in the threaded RTS
 215
 216 start:
 217 #if 0
 218     fprintf(stderr, "awaitRequests(): %d %d %d\n", issued_reqs, completed_hw, wait);
 219     fflush(stderr);
 220 #endif
 221     EnterCriticalSection(&queue_lock);
 222     /* Nothing immediately available & we won't wait */
 223     if ((!wait && completed_hw == 0)
 224 #if 0
 225         // If we just return when wait==rtsFalse, we'll go into a busy
 226         // wait loop, so I disabled this condition --SDM 18/12/2003
 227         (issued_reqs == 0 && completed_hw == 0)
 228 #endif
 229         ) {
 230         LeaveCriticalSection(&queue_lock);
 231         return 0;
 232     }
 233     if (completed_hw == 0) {
 234         /* empty table, drop lock and wait */
 235         LeaveCriticalSection(&queue_lock);
 236         if ( wait && sched_state == SCHED_RUNNING ) {
 237             DWORD dwRes = WaitForMultipleObjects(2, wait_handles, FALSE, INFINITE);
 238             switch (dwRes) {
 239             case WAIT_OBJECT_0:
 240                 /* a request was completed */
 241                 break;
 242             case WAIT_OBJECT_0 + 1:
 243             case WAIT_TIMEOUT:
 244                 /* timeout (unlikely) or told to abandon waiting */
 245                 return 0;
 246             case WAIT_FAILED: {
 247                 DWORD dw = GetLastError();
 248                 fprintf(stderr, "awaitRequests: wait failed -- error code: %lu\n", dw); fflush(stderr);
 249                 return 0;
 250             }
 251             default:
 252                 fprintf(stderr, "awaitRequests: unexpected wait return code %lu\n", dwRes); fflush(stderr);
 253                 return 0;
 254             }
 255         } else {
 256             return 0;
 257         }
 258         goto start;
 259     } else {
 260         int i;
 261         StgTSO *tso, *prev;
 262
 263         for (i=0; i < completed_hw; i++) {
 264             /* For each of the completed requests, match up their Ids
 265              * with those of the threads on the blocked_queue. If the
 266              * thread that made the IO request has been subsequently
 267              * killed (and removed from blocked_queue), no match will
 268              * be found for that request Id.
 269              *
 270              * i.e., killing a Haskell thread doesn't attempt to cancel
 271              * the IO request it is blocked on.
 272              *
 273              */
 274             unsigned int rID = completedTable[i].reqID;
 275
 276             prev = NULL;
 277             for(tso = blocked_queue_hd ; tso != END_TSO_QUEUE; prev = tso, tso = tso->link) {
 278
 279                 switch(tso->why_blocked) {
 280                 case BlockedOnRead:
 281                 case BlockedOnWrite:
 282                 case BlockedOnDoProc:
 283                     if (tso->block_info.async_result->reqID == rID) {
 284                         /* Found the thread blocked waiting on request; stodgily fill
 285                          * in its result block.
 286                          */
 287                         tso->block_info.async_result->len = completedTable[i].len;
 288                         tso->block_info.async_result->errCode = completedTable[i].errCode;
 289
 290                         /* Drop the matched TSO from blocked_queue */
 291                         if (prev) {
 292                             prev->link = tso->link;
 293                         } else {
 294                             blocked_queue_hd = tso->link;
 295                         }
 296                         if (blocked_queue_tl == tso) {
 297                             blocked_queue_tl = prev ? prev : END_TSO_QUEUE;
 298                         }
 299
 300                         /* Terminates the run queue + this inner for-loop. */
 301                         tso->link = END_TSO_QUEUE;
 302                         tso->why_blocked = NotBlocked;
 303                         pushOnRunQueue(&MainCapability, tso);
 304                         break;
 305                     }
 306                     break;
 307                 default:
 308                     if (tso->why_blocked != NotBlocked) {
 309                         barf("awaitRequests: odd thread state");
 310                     }
 311                     break;
 312                 }
 313             }
 314             /* Signal that there's completed table slots available */
 315             if ( !ReleaseSemaphore(completed_table_sema, 1, NULL) ) {
 316                 DWORD dw = GetLastError();
 317                 fprintf(stderr, "awaitRequests: failed to signal semaphore (error code=0x%x)\n", (int)dw);
 318                 fflush(stderr);
 319             }
 320         }
 321         completed_hw = 0;
 322         ResetEvent(completed_req_event);
 323         LeaveCriticalSection(&queue_lock);
 324         return 1;
 325     }
 326 #endif /* !THREADED_RTS */
 327 }
 328
 329 /*
 330  * Function: abandonRequestWait()
 331  *
 332  * Wake up a thread that's blocked waiting for new IO requests
 333  * to complete (via awaitRequests().)
 334  */
 335 void
 336 abandonRequestWait( void )
 337 {
 338     /* the event is auto-reset, but in case there's no thread
 339      * already waiting on the event, we want to return it to
 340      * a non-signalled state.
 341      *
 342      * Careful!  There is no synchronisation between
 343      * abandonRequestWait and awaitRequest, which means that
 344      * abandonRequestWait might be called just before a thread
 345      * goes into a wait, and we miss the abandon signal.  So we
 346      * must SetEvent() here rather than PulseEvent() to ensure
 347      * that the event isn't lost.  We can re-optimise by resetting
 348      * the event somewhere safe if we know the event has been
 349      * properly serviced (see resetAbandon() below).  --SDM 18/12/2003
 350      */
 351     SetEvent(abandon_req_wait);
 352 }
 353
 354 void
 355 resetAbandonRequestWait( void )
 356 {
 357     ResetEvent(abandon_req_wait);
 358 }
 359
 360 #endif /* !defined(THREADED_RTS) */