ghc/rts/win32/IOManager.c

   1 /* IOManager.c
   2  *
   3  * Non-blocking / asynchronous I/O for Win32.
   4  *
   5  * (c) sof, 2002-2003.
   6  */
   7 #include "IOManager.h"
   8 #include "WorkQueue.h"
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <io.h>
  12 #include <winsock.h>
  13 #include <process.h>
  14
  15 /*
  16  * Internal state maintained by the IO manager.
  17  */
  18 typedef struct IOManagerState {
  19     CritSection      manLock;
  20     WorkQueue*       workQueue;
  21     int              queueSize;
  22     int              numWorkers;
  23     int              workersIdle;
  24     HANDLE           hExitEvent;
  25     unsigned int     requestID;
  26 } IOManagerState;
  27
  28 /* ToDo: wrap up this state via a IOManager handle instead? */
  29 static IOManagerState* ioMan;
  30
  31 /*
  32  * The routine executed by each worker thread.
  33  */
  34 static
  35 unsigned
  36 WINAPI
  37 IOWorkerProc(PVOID param)
  38 {
  39     HANDLE  hWaits[2];
  40     DWORD   rc;
  41     IOManagerState* iom = (IOManagerState*)param;
  42     WorkQueue* pq = iom->workQueue;
  43     WorkItem*  work;
  44     int        len = 0, fd = 0;
  45     DWORD      errCode = 0;
  46     void*      complData;
  47
  48     hWaits[0] = (HANDLE)iom->hExitEvent;
  49     hWaits[1] = GetWorkQueueHandle(pq);
  50
  51     while (1) {
  52         /* The error code is communicated back on completion of request; reset. */
  53         errCode = 0;
  54
  55         EnterCriticalSection(&iom->manLock);
  56         /* Signal that the worker is idle.
  57          *
  58          * 'workersIdle' is used when determining whether or not to
  59          * increase the worker thread pool when adding a new request.
  60          * (see addIORequest().)
  61          */
  62         iom->workersIdle++;
  63         LeaveCriticalSection(&iom->manLock);
  64
  65         /*
  66          * A possible future refinement is to make long-term idle threads
  67          * wake up and decide to shut down should the number of idle threads
  68          * be above some threshold.
  69          *
  70          */
  71         rc = WaitForMultipleObjects( 2, hWaits, FALSE, INFINITE );
  72
  73         if (rc == WAIT_OBJECT_0) {
  74             // we received the exit event
  75             return 0;
  76         }
  77
  78         EnterCriticalSection(&iom->manLock);
  79         /* Signal that the thread is 'non-idle' and about to consume
  80          * a work item.
  81          */
  82         iom->workersIdle--;
  83         iom->queueSize--;
  84         LeaveCriticalSection(&iom->manLock);
  85
  86         if ( rc == (WAIT_OBJECT_0 + 1) ) {
  87             /* work item available, fetch it. */
  88             if (FetchWork(pq,(void**)&work)) {
  89                 if ( work->workKind & WORKER_READ ) {
  90                     if ( work->workKind & WORKER_FOR_SOCKET ) {
  91                         len = recv(work->workData.ioData.fd,
  92                                    work->workData.ioData.buf,
  93                                    work->workData.ioData.len,
  94                                    0);
  95                         if (len == SOCKET_ERROR) {
  96                             errCode = WSAGetLastError();
  97                         }
  98                     } else {
  99                         DWORD dw;
 100
 101                         /* Do the read(), with extra-special handling for Ctrl+C */
 102                         len = read(work->workData.ioData.fd,
 103                                    work->workData.ioData.buf,
 104                                    work->workData.ioData.len);
 105                         if ( len == 0 && work->workData.ioData.len != 0 ) {
 106                             /* Given the following scenario:
 107                              *     - a console handler has been registered that handles Ctrl+C
 108                              *       events.
 109                              *     - we've not tweaked the 'console mode' settings to turn on
 110                              *       ENABLE_PROCESSED_INPUT.
 111                              *     - we're blocked waiting on input from standard input.
 112                              *     - the user hits Ctrl+C.
 113                              *
 114                              * The OS will invoke the console handler (in a separate OS thread),
 115                              * and the above read() (i.e., under the hood, a ReadFile() op) returns
 116                              * 0, with the error set to ERROR_OPERATION_ABORTED. We don't
 117                              * want to percolate this non-EOF condition too far back up, but ignore
 118                              * it. However, we do want to give the RTS an opportunity to deliver the
 119                              * console event.
 120                              *
 121                              * Hence, we set 'errorCode' to (-2), which we then look out for in
 122                              * GHC.Conc.asyncRead.
 123                              */
 124                             dw = GetLastError();
 125                             if ( dw == ERROR_OPERATION_ABORTED ) {
 126                                 /* Only do the retry when dealing with the standard input handle. */
 127                                 HANDLE h  = (HANDLE)GetStdHandle(STD_INPUT_HANDLE);
 128                                 if ( _get_osfhandle(work->workData.ioData.fd) == (long)h ) {
 129                                     errCode = (DWORD)-2;
 130                                 }
 131                             }
 132                         }
 133                         if (len == -1) { errCode = errno; }
 134                     }
 135                     complData = work->workData.ioData.buf;
 136                     fd = work->workData.ioData.fd;
 137                 } else if ( work->workKind & WORKER_WRITE ) {
 138                     if ( work->workKind & WORKER_FOR_SOCKET ) {
 139                         len = send(work->workData.ioData.fd,
 140                                    work->workData.ioData.buf,
 141                                    work->workData.ioData.len,
 142                                    0);
 143                         if (len == SOCKET_ERROR) {
 144                             errCode = WSAGetLastError();
 145                         }
 146                     } else {
 147                         len = write(work->workData.ioData.fd,
 148                                     work->workData.ioData.buf,
 149                                     work->workData.ioData.len);
 150                         if (len == -1) { errCode = errno; }
 151                     }
 152                     complData = work->workData.ioData.buf;
 153                     fd = work->workData.ioData.fd;
 154                 } else if ( work->workKind & WORKER_DELAY ) {
 155                     /* Approximate implementation of threadDelay;
 156                      *
 157                      * Note: Sleep() is in milliseconds, not micros.
 158                      */
 159                     Sleep(work->workData.delayData.msecs / 1000);
 160                     len = work->workData.delayData.msecs;
 161                     complData = NULL;
 162                     fd = 0;
 163                     errCode = 0;
 164                 } else if ( work->workKind & WORKER_DO_PROC ) {
 165                     /* perform operation/proc on behalf of Haskell thread. */
 166                     if (work->workData.procData.proc) {
 167                         /* The procedure is assumed to encode result + success/failure
 168                          * via its param.
 169                          */
 170                         errCode=work->workData.procData.proc(work->workData.procData.param);
 171                     } else {
 172                         errCode=1;
 173                     }
 174                     complData = work->workData.procData.param;
 175                 } else {
 176                     fprintf(stderr, "unknown work request type (%d) , ignoring.\n", work->workKind);
 177                     fflush(stderr);
 178                     continue;
 179                 }
 180                 work->onCompletion(work->requestID,
 181                                    fd,
 182                                    len,
 183                                    complData,
 184                                    errCode);
 185                 /* Free the WorkItem */
 186                 free(work);
 187             } else {
 188                 fprintf(stderr, "unable to fetch work; fatal.\n"); fflush(stderr);
 189                 return 1;
 190             }
 191         } else {
 192             fprintf(stderr, "waiting failed; fatal.\n"); fflush(stderr);
 193             return 1;
 194         }
 195     }
 196     return 0;
 197 }
 198
 199 static
 200 BOOL
 201 NewIOWorkerThread(IOManagerState* iom)
 202 {
 203     unsigned threadId;
 204     return ( 0 != _beginthreadex(NULL,
 205                                  0,
 206                                  IOWorkerProc,
 207                                  (LPVOID)iom,
 208                                  0,
 209                                  &threadId) );
 210 }
 211
 212 BOOL
 213 StartIOManager(void)
 214 {
 215     HANDLE hExit;
 216     WorkQueue* wq;
 217
 218     wq = NewWorkQueue();
 219     if ( !wq ) return FALSE;
 220
 221     ioMan = (IOManagerState*)malloc(sizeof(IOManagerState));
 222
 223     if (!ioMan) {
 224         FreeWorkQueue(wq);
 225         return FALSE;
 226     }
 227
 228     /* A manual-reset event */
 229     hExit = CreateEvent ( NULL, TRUE, FALSE, NULL );
 230     if ( !hExit ) {
 231         FreeWorkQueue(wq);
 232         free(ioMan);
 233         return FALSE;
 234     }
 235
 236     ioMan->hExitEvent = hExit;
 237     InitializeCriticalSection(&ioMan->manLock);
 238     ioMan->workQueue   = wq;
 239     ioMan->numWorkers  = 0;
 240     ioMan->workersIdle = 0;
 241     ioMan->queueSize   = 0;
 242     ioMan->requestID   = 1;
 243
 244     return TRUE;
 245 }
 246
 247 /*
 248  * Function: depositWorkItem()
 249  *
 250  * Local function which deposits a WorkItem onto a work queue,
 251  * deciding in the process whether or not the thread pool needs
 252  * to be augmented with another thread to handle the new request.
 253  *
 254  */
 255 static
 256 int
 257 depositWorkItem( unsigned int reqID,
 258                  WorkItem* wItem )
 259 {
 260     EnterCriticalSection(&ioMan->manLock);
 261
 262 #if 0
 263     fprintf(stderr, "depositWorkItem: %d/%d\n", ioMan->workersIdle, ioMan->numWorkers);
 264     fflush(stderr);
 265 #endif
 266     /* A new worker thread is created when there are fewer idle threads
 267      * than non-consumed queue requests. This ensures that requests will
 268      * be dealt with in a timely manner.
 269      *
 270      * [Long explanation of why the previous thread pool policy lead to
 271      * trouble]
 272      *
 273      * Previously, the thread pool was augmented iff no idle worker threads
 274      * were available. That strategy runs the risk of repeatedly adding to
 275      * the request queue without expanding the thread pool to handle this
 276      * sudden spike in queued requests.
 277      * [How? Assume workersIdle is 1, and addIORequest() is called. No new
 278      * thread is created and the request is simply queued. If addIORequest()
 279      * is called again _before the OS schedules a worker thread to pull the
 280      * request off the queue_, workersIdle is still 1 and another request is
 281      * simply added to the queue. Once the worker thread is run, only one
 282      * request is de-queued, leaving the 2nd request in the queue]
 283      *
 284      * Assuming none of the queued requests take an inordinate amount of to
 285      * complete, the request queue would eventually be drained. But if that's
 286      * not the case, the later requests will end up languishing in the queue
 287      * indefinitely. The non-timely handling of requests may cause CH applications
 288      * to misbehave / hang; bad.
 289      *
 290      */
 291     ioMan->queueSize++;
 292     if ( (ioMan->workersIdle < ioMan->queueSize) ) {
 293         /* see if giving up our quantum ferrets out some idle threads.
 294          */
 295         LeaveCriticalSection(&ioMan->manLock);
 296         Sleep(0);
 297         EnterCriticalSection(&ioMan->manLock);
 298         if ( (ioMan->workersIdle < ioMan->queueSize) ) {
 299             /* No, go ahead and create another. */
 300             ioMan->numWorkers++;
 301             LeaveCriticalSection(&ioMan->manLock);
 302             NewIOWorkerThread(ioMan);
 303         } else {
 304             LeaveCriticalSection(&ioMan->manLock);
 305         }
 306     } else {
 307         LeaveCriticalSection(&ioMan->manLock);
 308     }
 309
 310     if (SubmitWork(ioMan->workQueue,wItem)) {
 311         /* Note: the work item has potentially been consumed by a worker thread
 312          *       (and freed) at this point, so we cannot use wItem's requestID.
 313          */
 314         return reqID;
 315     } else {
 316         return 0;
 317     }
 318 }
 319
 320 /*
 321  * Function: AddIORequest()
 322  *
 323  * Conduit to underlying WorkQueue's SubmitWork(); adds IO
 324  * request to work queue, deciding whether or not to augment
 325  * the thread pool in the process.
 326  */
 327 int
 328 AddIORequest ( int   fd,
 329                BOOL  forWriting,
 330                BOOL  isSocket,
 331                int   len,
 332                char* buffer,
 333                CompletionProc onCompletion)
 334 {
 335     WorkItem* wItem    = (WorkItem*)malloc(sizeof(WorkItem));
 336     unsigned int reqID = ioMan->requestID++;
 337     if (!ioMan || !wItem) return 0;
 338
 339     /* Fill in the blanks */
 340     wItem->workKind     = ( isSocket   ? WORKER_FOR_SOCKET : 0 ) |
 341                           ( forWriting ? WORKER_WRITE : WORKER_READ );
 342     wItem->workData.ioData.fd  = fd;
 343     wItem->workData.ioData.len = len;
 344     wItem->workData.ioData.buf = buffer;
 345
 346     wItem->onCompletion        = onCompletion;
 347     wItem->requestID           = reqID;
 348
 349     return depositWorkItem(reqID, wItem);
 350 }
 351
 352 /*
 353  * Function: AddDelayRequest()
 354  *
 355  * Like AddIORequest(), but this time adding a delay request to
 356  * the request queue.
 357  */
 358 BOOL
 359 AddDelayRequest ( unsigned int   msecs,
 360                   CompletionProc onCompletion)
 361 {
 362     WorkItem* wItem = (WorkItem*)malloc(sizeof(WorkItem));
 363     unsigned int reqID = ioMan->requestID++;
 364     if (!ioMan || !wItem) return FALSE;
 365
 366     /* Fill in the blanks */
 367     wItem->workKind     = WORKER_DELAY;
 368     wItem->workData.delayData.msecs = msecs;
 369     wItem->onCompletion = onCompletion;
 370     wItem->requestID    = reqID;
 371
 372     return depositWorkItem(reqID, wItem);
 373 }
 374
 375 /*
 376  * Function: AddProcRequest()
 377  *
 378  * Add an asynchronous procedure request.
 379  */
 380 BOOL
 381 AddProcRequest ( void* proc,
 382                  void* param,
 383                  CompletionProc onCompletion)
 384 {
 385     WorkItem* wItem = (WorkItem*)malloc(sizeof(WorkItem));
 386     unsigned int reqID = ioMan->requestID++;
 387     if (!ioMan || !wItem) return FALSE;
 388
 389     /* Fill in the blanks */
 390     wItem->workKind     = WORKER_DO_PROC;
 391     wItem->workData.procData.proc  = proc;
 392     wItem->workData.procData.param = param;
 393     wItem->onCompletion = onCompletion;
 394     wItem->requestID    = reqID;
 395
 396     return depositWorkItem(reqID, wItem);
 397 }
 398
 399 void ShutdownIOManager ( void )
 400 {
 401   SetEvent(ioMan->hExitEvent);
 402   // ToDo: we can't free this now, because the worker thread(s)
 403   // haven't necessarily finished with it yet.  Perhaps it should
 404   // have a reference count or something.
 405   // free(ioMan);
 406   // ioMan = NULL;
 407 }