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;
  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         EnterCriticalSection(&iom->manLock);
  74         /* Signal that the thread is 'non-idle' and about to consume
  75          * a work item.
  76          */
  77         iom->workersIdle--;
  78         iom->queueSize--;
  79         LeaveCriticalSection(&iom->manLock);
  80
  81         if ( WAIT_OBJECT_0 == rc ) {
  82             /* shutdown */
  83             return 0;
  84         } else if ( (WAIT_OBJECT_0 + 1) == rc ) {
  85             /* work item available, fetch it. */
  86             if (FetchWork(pq,(void**)&work)) {
  87                 if ( work->workKind & WORKER_READ ) {
  88                     if ( work->workKind & WORKER_FOR_SOCKET ) {
  89                         len = recv(work->workData.ioData.fd,
  90                                    work->workData.ioData.buf,
  91                                    work->workData.ioData.len,
  92                                    0);
  93                         if (len == SOCKET_ERROR) {
  94                             errCode = WSAGetLastError();
  95                         }
  96                     } else {
  97                         len = read(work->workData.ioData.fd,
  98                                    work->workData.ioData.buf,
  99                                    work->workData.ioData.len);
 100                         if (len == -1) { errCode = errno; }
 101                     }
 102                     complData = work->workData.ioData.buf;
 103                     fd = work->workData.ioData.fd;
 104                 } else if ( work->workKind & WORKER_WRITE ) {
 105                     if ( work->workKind & WORKER_FOR_SOCKET ) {
 106                         len = send(work->workData.ioData.fd,
 107                                    work->workData.ioData.buf,
 108                                    work->workData.ioData.len,
 109                                    0);
 110                         if (len == SOCKET_ERROR) {
 111                             errCode = WSAGetLastError();
 112                         }
 113                     } else {
 114                         len = write(work->workData.ioData.fd,
 115                                     work->workData.ioData.buf,
 116                                     work->workData.ioData.len);
 117                         if (len == -1) { errCode = errno; }
 118                     }
 119                     complData = work->workData.ioData.buf;
 120                     fd = work->workData.ioData.fd;
 121                 } else if ( work->workKind & WORKER_DELAY ) {
 122                     /* Approximate implementation of threadDelay;
 123                      *
 124                      * Note: Sleep() is in milliseconds, not micros.
 125                      */
 126                     Sleep(work->workData.delayData.msecs / 1000);
 127                     len = work->workData.delayData.msecs;
 128                     complData = NULL;
 129                     fd = 0;
 130                     errCode = 0;
 131                 } else if ( work->workKind & WORKER_DO_PROC ) {
 132                     /* perform operation/proc on behalf of Haskell thread. */
 133                     if (work->workData.procData.proc) {
 134                         /* The procedure is assumed to encode result + success/failure
 135                          * via its param.
 136                          */
 137                         errCode=work->workData.procData.proc(work->workData.procData.param);
 138                     } else {
 139                         errCode=1;
 140                     }
 141                     complData = work->workData.procData.param;
 142                 } else {
 143                     fprintf(stderr, "unknown work request type (%d) , ignoring.\n", work->workKind);
 144                     fflush(stderr);
 145                     continue;
 146                 }
 147                 work->onCompletion(work->requestID,
 148                                    fd,
 149                                    len,
 150                                    complData,
 151                                    errCode);
 152                 /* Free the WorkItem */
 153                 free(work);
 154             } else {
 155                 fprintf(stderr, "unable to fetch work; fatal.\n"); fflush(stderr);
 156                 return 1;
 157             }
 158         } else {
 159             fprintf(stderr, "waiting failed; fatal.\n"); fflush(stderr);
 160             return 1;
 161         }
 162     }
 163     return 0;
 164 }
 165
 166 static
 167 BOOL
 168 NewIOWorkerThread(IOManagerState* iom)
 169 {
 170     unsigned threadId;
 171     return ( 0 != _beginthreadex(NULL,
 172                                  0,
 173                                  IOWorkerProc,
 174                                  (LPVOID)iom,
 175                                  0,
 176                                  &threadId) );
 177 }
 178
 179 BOOL
 180 StartIOManager(void)
 181 {
 182     HANDLE hExit;
 183     WorkQueue* wq;
 184
 185     wq = NewWorkQueue();
 186     if ( !wq ) return FALSE;
 187
 188     ioMan = (IOManagerState*)malloc(sizeof(IOManagerState));
 189
 190     if (!ioMan) {
 191         FreeWorkQueue(wq);
 192         return FALSE;
 193     }
 194
 195     /* A manual-reset event */
 196     hExit = CreateEvent ( NULL, TRUE, FALSE, NULL );
 197     if ( !hExit ) {
 198         FreeWorkQueue(wq);
 199         free(ioMan);
 200         return FALSE;
 201     }
 202
 203     ioMan->hExitEvent = hExit;
 204     InitializeCriticalSection(&ioMan->manLock);
 205     ioMan->workQueue   = wq;
 206     ioMan->numWorkers  = 0;
 207     ioMan->workersIdle = 0;
 208     ioMan->queueSize   = 0;
 209     ioMan->requestID   = 1;
 210
 211     return TRUE;
 212 }
 213
 214 /*
 215  * Function: depositWorkItem()
 216  *
 217  * Local function which deposits a WorkItem onto a work queue,
 218  * deciding in the process whether or not the thread pool needs
 219  * to be augmented with another thread to handle the new request.
 220  *
 221  */
 222 static
 223 int
 224 depositWorkItem( unsigned int reqID,
 225                  WorkItem* wItem )
 226 {
 227     EnterCriticalSection(&ioMan->manLock);
 228
 229 #if 0
 230     fprintf(stderr, "depositWorkItem: %d/%d\n", ioMan->workersIdle, ioMan->numWorkers);
 231     fflush(stderr);
 232 #endif
 233     /* A new worker thread is created when there are fewer idle threads
 234      * than non-consumed queue requests. This ensures that requests will
 235      * be dealt with in a timely manner.
 236      *
 237      * [Long explanation of why the previous thread pool policy lead to
 238      * trouble]
 239      *
 240      * Previously, the thread pool was augmented iff no idle worker threads
 241      * were available. That strategy runs the risk of repeatedly adding to
 242      * the request queue without expanding the thread pool to handle this
 243      * sudden spike in queued requests.
 244      * [How? Assume workersIdle is 1, and addIORequest() is called. No new
 245      * thread is created and the request is simply queued. If addIORequest()
 246      * is called again _before the OS schedules a worker thread to pull the
 247      * request off the queue_, workersIdle is still 1 and another request is
 248      * simply added to the queue. Once the worker thread is run, only one
 249      * request is de-queued, leaving the 2nd request in the queue]
 250      *
 251      * Assuming none of the queued requests take an inordinate amount of to
 252      * complete, the request queue would eventually be drained. But if that's
 253      * not the case, the later requests will end up languishing in the queue
 254      * indefinitely. The non-timely handling of requests may cause CH applications
 255      * to misbehave / hang; bad.
 256      *
 257      */
 258     ioMan->queueSize++;
 259     if ( (ioMan->workersIdle < ioMan->queueSize) ) {
 260         /* see if giving up our quantum ferrets out some idle threads.
 261          */
 262         LeaveCriticalSection(&ioMan->manLock);
 263         Sleep(0);
 264         EnterCriticalSection(&ioMan->manLock);
 265         if ( (ioMan->workersIdle < ioMan->queueSize) ) {
 266             /* No, go ahead and create another. */
 267             ioMan->numWorkers++;
 268             LeaveCriticalSection(&ioMan->manLock);
 269             NewIOWorkerThread(ioMan);
 270         } else {
 271             LeaveCriticalSection(&ioMan->manLock);
 272         }
 273     } else {
 274         LeaveCriticalSection(&ioMan->manLock);
 275     }
 276
 277     if (SubmitWork(ioMan->workQueue,wItem)) {
 278         /* Note: the work item has potentially been consumed by a worker thread
 279          *       (and freed) at this point, so we cannot use wItem's requestID.
 280          */
 281         return reqID;
 282     } else {
 283         return 0;
 284     }
 285 }
 286
 287 /*
 288  * Function: AddIORequest()
 289  *
 290  * Conduit to underlying WorkQueue's SubmitWork(); adds IO
 291  * request to work queue, deciding whether or not to augment
 292  * the thread pool in the process.
 293  */
 294 int
 295 AddIORequest ( int   fd,
 296                BOOL  forWriting,
 297                BOOL  isSocket,
 298                int   len,
 299                char* buffer,
 300                CompletionProc onCompletion)
 301 {
 302     WorkItem* wItem    = (WorkItem*)malloc(sizeof(WorkItem));
 303     unsigned int reqID = ioMan->requestID++;
 304     if (!ioMan || !wItem) return 0;
 305
 306     /* Fill in the blanks */
 307     wItem->workKind     = ( isSocket   ? WORKER_FOR_SOCKET : 0 ) |
 308                           ( forWriting ? WORKER_WRITE : WORKER_READ );
 309     wItem->workData.ioData.fd  = fd;
 310     wItem->workData.ioData.len = len;
 311     wItem->workData.ioData.buf = buffer;
 312
 313     wItem->onCompletion        = onCompletion;
 314     wItem->requestID           = reqID;
 315
 316     return depositWorkItem(reqID, wItem);
 317 }
 318
 319 /*
 320  * Function: AddDelayRequest()
 321  *
 322  * Like AddIORequest(), but this time adding a delay request to
 323  * the request queue.
 324  */
 325 BOOL
 326 AddDelayRequest ( unsigned int   msecs,
 327                   CompletionProc onCompletion)
 328 {
 329     WorkItem* wItem = (WorkItem*)malloc(sizeof(WorkItem));
 330     unsigned int reqID = ioMan->requestID++;
 331     if (!ioMan || !wItem) return FALSE;
 332
 333     /* Fill in the blanks */
 334     wItem->workKind     = WORKER_DELAY;
 335     wItem->workData.delayData.msecs = msecs;
 336     wItem->onCompletion = onCompletion;
 337     wItem->requestID    = reqID;
 338
 339     return depositWorkItem(reqID, wItem);
 340 }
 341
 342 /*
 343  * Function: AddProcRequest()
 344  *
 345  * Add an asynchronous procedure request.
 346  */
 347 BOOL
 348 AddProcRequest ( void* proc,
 349                  void* param,
 350                  CompletionProc onCompletion)
 351 {
 352     WorkItem* wItem = (WorkItem*)malloc(sizeof(WorkItem));
 353     unsigned int reqID = ioMan->requestID++;
 354     if (!ioMan || !wItem) return FALSE;
 355
 356     /* Fill in the blanks */
 357     wItem->workKind     = WORKER_DO_PROC;
 358     wItem->workData.procData.proc  = proc;
 359     wItem->workData.procData.param = param;
 360     wItem->onCompletion = onCompletion;
 361     wItem->requestID    = reqID;
 362
 363     return depositWorkItem(reqID, wItem);
 364 }
 365
 366 void ShutdownIOManager()
 367 {
 368   SetEvent(ioMan->hExitEvent);
 369   free(ioMan);
 370   ioMan = NULL;
 371 }