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