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/* AsyncIO.c
*
* Integrating Win32 asynchronous I/O with the GHC RTS.
*
* (c) sof, 2002-2003.
*/
#include "Rts.h"
#include "RtsUtils.h"
#include <windows.h>
#include <stdio.h>
#include "Schedule.h"
#include "win32/AsyncIO.h"
#include "win32/IOManager.h"
/*
* Overview:
*
* Haskell code issue asynchronous I/O requests via the
* asyncRead# and asyncWrite# primops. These cause addIORequest()
* to be invoked, which forwards the request to the underlying
* asynchronous I/O subsystem. Each request is tagged with a unique
* ID.
*
* addIORequest() returns this ID, so that when the blocked CH
* thread is added onto blocked_queue, its TSO is annotated with
* it. Upon completion of an I/O request, the async I/O handling
* code makes a back-call to signal its completion; the local
* onIOComplete() routine. It adds the IO request ID (along with
* its result data) to a queue of completed requests before returning.
*
* The queue of completed IO request is read by the thread operating
* the RTS scheduler. It de-queues the CH threads corresponding
* to the request IDs, making them runnable again.
*
*/
typedef struct CompletedReq {
unsigned int reqID;
int len;
int errCode;
} CompletedReq;
#define MAX_REQUESTS 200
static CRITICAL_SECTION queue_lock;
static HANDLE completed_req_event;
static HANDLE abandon_req_wait;
static HANDLE wait_handles[2];
static CompletedReq completedTable[MAX_REQUESTS];
static int completed_hw;
static int issued_reqs;
static void
onIOComplete(unsigned int reqID,
int fd STG_UNUSED,
int len,
void* buf STG_UNUSED,
int errCode)
{
/* Deposit result of request in queue/table */
EnterCriticalSection(&queue_lock);
if (completed_hw == MAX_REQUESTS) {
/* Not likely */
fprintf(stderr, "Request table overflow (%d); dropping.\n", reqID);
fflush(stderr);
} else {
#if 0
fprintf(stderr, "onCompl: %d %d %d %d %d\n", reqID, len, errCode, issued_reqs, completed_hw); fflush(stderr);
#endif
completedTable[completed_hw].reqID = reqID;
completedTable[completed_hw].len = len;
completedTable[completed_hw].errCode = errCode;
completed_hw++;
issued_reqs--;
if (completed_hw == 1) {
/* The event is used to wake up the scheduler thread should it
* be blocked waiting for requests to complete. It reset once
* that thread has cleared out the request queue/table.
*/
SetEvent(completed_req_event);
}
}
LeaveCriticalSection(&queue_lock);
}
unsigned int
addIORequest(int fd,
int forWriting,
int isSock,
int len,
char* buf)
{
EnterCriticalSection(&queue_lock);
issued_reqs++;
LeaveCriticalSection(&queue_lock);
#if 0
fprintf(stderr, "addIOReq: %d %d %d\n", fd, forWriting, len); fflush(stderr);
#endif
return AddIORequest(fd,forWriting,isSock,len,buf,onIOComplete);
}
unsigned int
addDelayRequest(int msecs)
{
EnterCriticalSection(&queue_lock);
issued_reqs++;
LeaveCriticalSection(&queue_lock);
#if 0
fprintf(stderr, "addDelayReq: %d\n", msecs); fflush(stderr);
#endif
return AddDelayRequest(msecs,onIOComplete);
}
unsigned int
addDoProcRequest(void* proc, void* param)
{
EnterCriticalSection(&queue_lock);
issued_reqs++;
LeaveCriticalSection(&queue_lock);
#if 0
fprintf(stderr, "addProcReq: %p %p\n", proc, param); fflush(stderr);
#endif
return AddProcRequest(proc,param,onIOComplete);
}
int
startupAsyncIO()
{
if (!StartIOManager()) {
return 0;
}
InitializeCriticalSection(&queue_lock);
/* Create a pair of events:
*
* - completed_req_event -- signals the deposit of request result; manual reset.
* - abandon_req_wait -- external OS thread tells current RTS/Scheduler
* thread to abandon wait for IO request completion.
* Auto reset.
*/
completed_req_event = CreateEvent (NULL, TRUE, FALSE, NULL);
abandon_req_wait = CreateEvent (NULL, FALSE, FALSE, NULL);
wait_handles[0] = completed_req_event;
wait_handles[1] = abandon_req_wait;
completed_hw = 0;
return ( completed_req_event != INVALID_HANDLE_VALUE &&
abandon_req_wait != INVALID_HANDLE_VALUE );
}
void
shutdownAsyncIO()
{
CloseHandle(completed_req_event);
ShutdownIOManager();
}
int
awaitRequests(rtsBool wait)
{
start:
#if 0
fprintf(stderr, "awaitRequests: %d %d %d\n", issued_reqs, completed_hw, wait); fflush(stderr);
#endif
EnterCriticalSection(&queue_lock);
/* Nothing immediately available & we won't wait */
if ((!wait && completed_hw == 0) ||
(issued_reqs == 0 && completed_hw == 0)) {
LeaveCriticalSection(&queue_lock);
return 0;
}
if (completed_hw == 0) {
/* empty table, drop lock and wait */
LeaveCriticalSection(&queue_lock);
if (wait) {
DWORD dwRes = WaitForMultipleObjects(2, wait_handles, FALSE, INFINITE);
switch (dwRes) {
case WAIT_OBJECT_0:
break;
case WAIT_OBJECT_0 + 1:
case WAIT_TIMEOUT:
return 0;
default:
fprintf(stderr, "awaitRequests: unexpected wait return code %lu\n", dwRes); fflush(stderr);
return 0;
}
} else {
return 0; /* cannot happen */
}
goto start;
} else {
int i;
StgTSO *tso, *prev;
for (i=0; i < completed_hw; i++) {
unsigned int rID = completedTable[i].reqID;
prev = NULL;
for(tso = blocked_queue_hd ; tso != END_TSO_QUEUE; tso = tso->link) {
switch(tso->why_blocked) {
case BlockedOnRead:
case BlockedOnWrite:
case BlockedOnDoProc:
if (tso->block_info.async_result->reqID == rID) {
/* Found the thread blocked waiting on request; stodgily fill
* in its result block.
*/
tso->block_info.async_result->len = completedTable[i].len;
tso->block_info.async_result->errCode = completedTable[i].errCode;
/* Drop the matched TSO from blocked_queue */
if (prev) {
prev->link = tso->link;
} else {
blocked_queue_hd = tso->link;
}
if (blocked_queue_tl == tso) {
blocked_queue_tl = prev;
}
/* Terminates the run queue + this inner for-loop. */
tso->link = END_TSO_QUEUE;
tso->why_blocked = NotBlocked;
PUSH_ON_RUN_QUEUE(tso);
break;
}
break;
default:
if (tso->why_blocked != NotBlocked) {
barf("awaitRequests: odd thread state");
}
break;
}
prev = tso;
}
}
completed_hw = 0;
ResetEvent(completed_req_event);
LeaveCriticalSection(&queue_lock);
return 1;
}
}
void
abandonRequestWait()
{
/* the event is auto-reset, but in case there's no thread
* already waiting on the event, we want to return it to
* a non-signalled state.
*/
PulseEvent(abandon_req_wait);
}
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