path: root/macosx/tclMacOSXNotify.c

/*
 * tclMacOSXNotify.c --
 *
 *	This file contains the implementation of a merged 
 *	CFRunLoop/select-based notifier, which is the lowest-level part 
 *	of the Tcl event loop.  This file works together with
 *	generic/tclNotify.c.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 * Copyright 2001, Apple Computer, Inc.
 * Copyright 2005, Tcl Core Team.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclMacOSXNotify.c,v 1.1 2005/05/14 20:46:46 das Exp $
 */

#ifdef HAVE_COREFOUNDATION /* Traditional unix select-based notifier
                            * is in tclUnixNotfy.c */ 
#include "tclInt.h"
#include <CoreFoundation/CoreFoundation.h>
#include <pthread.h>

extern TclStubs tclStubs;
extern Tcl_NotifierProcs tclOriginalNotifier;

/*
 * This structure is used to keep track of the notifier info for a 
 * a registered file.
 */

typedef struct FileHandler {
    int fd;
    int mask;			/* Mask of desired events: TCL_READABLE,
				 * etc. */
    int readyMask;		/* Mask of events that have been seen since the
				 * last time file handlers were invoked for
				 * this file. */
    Tcl_FileProc *proc;		/* Procedure to call, in the style of
				 * Tcl_CreateFileHandler. */
    ClientData clientData;	/* Argument to pass to proc. */
    struct FileHandler *nextPtr;/* Next in list of all files we care about. */
} FileHandler;

/*
 * The following structure is what is added to the Tcl event queue when
 * file handlers are ready to fire.
 */

typedef struct FileHandlerEvent {
    Tcl_Event header;		/* Information that is standard for
				 * all events. */
    int fd;			/* File descriptor that is ready.  Used
				 * to find the FileHandler structure for
				 * the file (can't point directly to the
				 * FileHandler structure because it could
				 * go away while the event is queued). */
} FileHandlerEvent;

/*
 *
 * The following structure contains a set of select() masks to track
 * readable, writable, and exceptional conditions.
 */

typedef struct SelectMasks {
    fd_set readable;
    fd_set writable;
    fd_set exceptional;
} SelectMasks;

/*
 * The following static structure contains the state information for the
 * select based implementation of the Tcl notifier.  One of these structures
 * is created for each thread that is using the notifier.  
 */

typedef struct ThreadSpecificData {
    FileHandler *firstFileHandlerPtr;
				/* Pointer to head of file handler list. */

    SelectMasks checkMasks;	/* This structure is used to build up the masks
				 * to be used in the next call to select.
				 * Bits are set in response to calls to
				 * Tcl_CreateFileHandler. */
    SelectMasks readyMasks;	/* This array reflects the readable/writable
				 * conditions that were found to exist by the
				 * last call to select. */
    int numFdBits;		/* Number of valid bits in checkMasks
				 * (one more than highest fd for which
				 * Tcl_WatchFile has been called). */
    int onList;			/* True if it is in this list */
    unsigned int pollState;	/* pollState is used to implement a polling 
				 * handshake between each thread and the
				 * notifier thread. Bits defined below. */
    struct ThreadSpecificData *nextPtr, *prevPtr;
				/* All threads that are currently waiting on 
				 * an event have their ThreadSpecificData
				 * structure on a doubly-linked listed formed
				 * from these pointers.  You must hold the
				 * notifierLock before accessing these
				 * fields. */
    CFRunLoopSourceRef runLoopSource;
                                /* Any other thread alerts a notifier
				 * that an event is ready to be processed
				 * by signaling this CFRunLoopSource. */
    CFRunLoopRef runLoop;       /* This thread's CFRunLoop, needs to be woken
                                 * up whenever the runLoopSource is signaled. */
    int eventReady;		/* True if an event is ready to be processed. */
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * The following static indicates the number of threads that have
 * initialized notifiers.
 *
 * You must hold the notifierInitLock before accessing this variable.
 */

static int notifierCount = 0;

/*
 * The following variable points to the head of a doubly-linked list of 
 * of ThreadSpecificData structures for all threads that are currently
 * waiting on an event.
 *
 * You must hold the notifierLock before accessing this list.
 */

static ThreadSpecificData *waitingListPtr = NULL;

/*
 * The notifier thread spends all its time in select() waiting for a
 * file descriptor associated with one of the threads on the waitingListPtr
 * list to do something interesting.  But if the contents of the
 * waitingListPtr list ever changes, we need to wake up and restart
 * the select() system call.  You can wake up the notifier thread by
 * writing a single byte to the file descriptor defined below.  This
 * file descriptor is the input-end of a pipe and the notifier thread is
 * listening for data on the output-end of the same pipe.  Hence writing
 * to this file descriptor will cause the select() system call to return
 * and wake up the notifier thread.
 *
 * You must hold the notifierLock lock before writing to the pipe.
 */

static int triggerPipe = -1;
static int receivePipe = -1; /* Output end of triggerPipe */

/*
 * We use Darwin-native spinlocks instead of pthread mutexes for notifier
 * locking: this radically simplifies the implementation and lowers
 * overhead. Note that these are not pure spinlocks, they employ various
 * strategies to back off, making them immune to most priority-inversion
 * livelocks (c.f. man 3 OSSpinLockLock).
 */

#if defined(HAVE_LIBKERN_OSATOMIC_H) && defined(HAVE_OSSPINLOCKLOCK)
/* Use OSSpinLock API where available (Tiger or later) */
#include <libkern/OSAtomic.h>
#else
/* Otherwise, use commpage spinlock SPI directly */
typedef uint32_t OSSpinLock;
extern void _spin_lock(OSSpinLock *lock);
extern void _spin_unlock(OSSpinLock *lock);
#define OSSpinLockLock(p) _spin_lock(p)
#define OSSpinLockUnlock(p) _spin_unlock(p)
#endif

/*
 * These spinlocks lock access to the global notifier state. 
 */

static OSSpinLock notifierInitLock = 0;
static OSSpinLock notifierLock = 0;

/* 
 * Macros abstracting notifier locking/unlocking
 */

#define LOCK_NOTIFIER_INIT   OSSpinLockLock(&notifierInitLock)
#define UNLOCK_NOTIFIER_INIT OSSpinLockUnlock(&notifierInitLock)
#define LOCK_NOTIFIER        OSSpinLockLock(&notifierLock)
#define UNLOCK_NOTIFIER      OSSpinLockUnlock(&notifierLock)

/*
 * The pollState bits
 *	POLL_WANT is set by each thread before it waits on its condition
 *		variable.  It is checked by the notifier before it does
 *		select.
 *	POLL_DONE is set by the notifier if it goes into select after
 *		seeing POLL_WANT.  The idea is to ensure it tries a select
 *		with the same bits the initial thread had set.
 */
#define POLL_WANT	0x1
#define POLL_DONE	0x2

/*
 * This is the thread ID of the notifier thread that does select.
 */
static pthread_t notifierThread;

/*
 * Static routines defined in this file.
 */

static void	NotifierThreadProc(ClientData clientData);
static int	FileHandlerEventProc(Tcl_Event *evPtr, int flags);

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InitNotifier --
 *
 *	Initializes the platform specific notifier state.
 *
 * Results:
 *	Returns a handle to the notifier state for this thread..
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_InitNotifier()
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    tsdPtr->eventReady = 0;
    
     /*
     * Initialize CFRunLoopSource and add it to CFRunLoop of this thread
     */
    
    if (!tsdPtr->runLoop) {
        CFRunLoopRef runLoop = CFRunLoopGetCurrent();
        CFRunLoopSourceRef runLoopSource;
        CFRunLoopSourceContext runLoopSourceContext;
        
        bzero(&runLoopSourceContext, sizeof(CFRunLoopSourceContext));
        runLoopSourceContext.info = tsdPtr;
        runLoopSource = CFRunLoopSourceCreate(NULL, 0, &runLoopSourceContext);
        if (!runLoopSource) {
            Tcl_Panic("Tcl_InitNotifier: could not create CFRunLoopSource.");
        }
        CFRunLoopAddSource(runLoop, runLoopSource, kCFRunLoopCommonModes);
        CFRelease(runLoopSource);
        tsdPtr->runLoopSource = runLoopSource;
        tsdPtr->runLoop = runLoop;
    }

    /*
     * Initialize trigger pipe and start the Notifier thread if necessary.
     */

    LOCK_NOTIFIER_INIT;
    if (notifierCount == 0) {
        int fds[2], status, result;
        pthread_attr_t attr;
    
        if (pipe(fds) != 0) {
            Tcl_Panic("Tcl_InitNotifier: could not create trigger pipe.");
        }
        
        status = fcntl(fds[0], F_GETFL);
        status |= O_NONBLOCK;
        if (fcntl(fds[0], F_SETFL, status) < 0) {
            Tcl_Panic("Tcl_InitNotifier: could not make receive pipe non blocking.");
        }
        status = fcntl(fds[1], F_GETFL);
        status |= O_NONBLOCK;
        if (fcntl(fds[1], F_SETFL, status) < 0) {
            Tcl_Panic("Tcl_InitNotifier: could not make trigger pipe non blocking.");
        }

        receivePipe = fds[0];
        triggerPipe = fds[1];

        pthread_attr_init(&attr);
        pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM);
        pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
        pthread_attr_setstacksize(&attr, 60 * 1024);
        result = pthread_create(&notifierThread, &attr, (void * (*)(void *))NotifierThreadProc, NULL);
        pthread_attr_destroy(&attr);
	if (result) {
	    Tcl_Panic("Tcl_InitNotifier: unable to start notifier thread.");
	}
    }
    notifierCount++;
    UNLOCK_NOTIFIER_INIT;
    
    return (ClientData) tsdPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FinalizeNotifier --
 *
 *	This function is called to cleanup the notifier state before
 *	a thread is terminated.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May terminate the background notifier thread if this is the
 *	last notifier instance.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_FinalizeNotifier(clientData)
    ClientData clientData;		/* Not used. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    LOCK_NOTIFIER_INIT;
    notifierCount--;

    /*
     * If this is the last thread to use the notifier, close the notifier
     * pipe and wait for the background thread to terminate.
     */

    if (notifierCount == 0) {
        int result;
        
	if (triggerPipe < 0) {
	    Tcl_Panic("Tcl_FinalizeNotifier: notifier pipe not initialized.");
	}

	/*
	 * Send "q" message to the notifier thread so that it will
	 * terminate.  The notifier will return from its call to select()
	 * and notice that a "q" message has arrived, it will then close
	 * its side of the pipe and terminate its thread.  Note the we can
	 * not just close the pipe and check for EOF in the notifier
	 * thread because if a background child process was created with
	 * exec, select() would not register the EOF on the pipe until the
	 * child processes had terminated. [Bug: 4139]
	 */
	write(triggerPipe, "q", 1);
	close(triggerPipe);

	result = pthread_join(notifierThread, NULL); 
	if (result) {
	    Tcl_Panic("Tcl_FinalizeNotifier: unable to join notifier thread.");
	}
	
	close(receivePipe);
        triggerPipe = -1;
    }
    UNLOCK_NOTIFIER_INIT;
    
    LOCK_NOTIFIER; /* for concurrency with Tcl_AlertNotifier */
    if (tsdPtr->runLoop) {
        tsdPtr->runLoop = NULL;
        /* Remove runLoopSource from all CFRunLoops and release it */
        CFRunLoopSourceInvalidate(tsdPtr->runLoopSource);
        tsdPtr->runLoopSource = NULL;
    }
    UNLOCK_NOTIFIER;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AlertNotifier --
 *
 *	Wake up the specified notifier from any thread. This routine
 *	is called by the platform independent notifier code whenever
 *	the Tcl_ThreadAlert routine is called.  This routine is
 *	guaranteed not to be called on a given notifier after
 *	Tcl_FinalizeNotifier is called for that notifier.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Signals the notifier condition variable for the specified
 *	notifier.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AlertNotifier(clientData)
    ClientData clientData;
{
    ThreadSpecificData *tsdPtr = (ThreadSpecificData *) clientData;
    LOCK_NOTIFIER;
    if (tsdPtr->runLoop) {
        tsdPtr->eventReady = 1;
        CFRunLoopSourceSignal(tsdPtr->runLoopSource);
        CFRunLoopWakeUp(tsdPtr->runLoop);
    }
    UNLOCK_NOTIFIER;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetTimer --
 *
 *	This procedure sets the current notifier timer value.  This
 *	interface is not implemented in this notifier because we are
 *	always running inside of Tcl_DoOneEvent.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetTimer(timePtr)
    Tcl_Time *timePtr;		/* Timeout value, may be NULL. */
{
    /*
     * The interval timer doesn't do anything in this implementation,
     * because the only event loop is via Tcl_DoOneEvent, which passes
     * timeout values to Tcl_WaitForEvent.
     */

    if (tclStubs.tcl_SetTimer != tclOriginalNotifier.setTimerProc) {
	tclStubs.tcl_SetTimer(timePtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ServiceModeHook --
 *
 *	This function is invoked whenever the service mode changes.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ServiceModeHook(mode)
    int mode;			/* Either TCL_SERVICE_ALL, or
				 * TCL_SERVICE_NONE. */
{
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateFileHandler --
 *
 *	This procedure registers a file handler with the select notifier.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new file handler structure.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateFileHandler(fd, mask, proc, clientData)
    int fd;			/* Handle of stream to watch. */
    int mask;			/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, and TCL_EXCEPTION:
				 * indicates conditions under which
				 * proc should be called. */
    Tcl_FileProc *proc;		/* Procedure to call for each
				 * selected event. */
    ClientData clientData;	/* Arbitrary data to pass to proc. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    FileHandler *filePtr;

    if (tclStubs.tcl_CreateFileHandler != tclOriginalNotifier.createFileHandlerProc) {
	tclStubs.tcl_CreateFileHandler(fd, mask, proc, clientData);
	return;
    }

    for (filePtr = tsdPtr->firstFileHandlerPtr; filePtr != NULL;
	    filePtr = filePtr->nextPtr) {
	if (filePtr->fd == fd) {
	    break;
	}
    }
    if (filePtr == NULL) {
	filePtr = (FileHandler*) ckalloc(sizeof(FileHandler));
	filePtr->fd = fd;
	filePtr->readyMask = 0;
	filePtr->nextPtr = tsdPtr->firstFileHandlerPtr;
	tsdPtr->firstFileHandlerPtr = filePtr;
    }
    filePtr->proc = proc;
    filePtr->clientData = clientData;
    filePtr->mask = mask;

    /*
     * Update the check masks for this file.
     */

    if (mask & TCL_READABLE) {
	FD_SET(fd, &(tsdPtr->checkMasks.readable));
    } else {
	FD_CLR(fd, &(tsdPtr->checkMasks.readable));
    }
    if (mask & TCL_WRITABLE) {
	FD_SET(fd, &(tsdPtr->checkMasks.writable));
    } else {
	FD_CLR(fd, &(tsdPtr->checkMasks.writable));
    }
    if (mask & TCL_EXCEPTION) {
	FD_SET(fd, &(tsdPtr->checkMasks.exceptional));
    } else {
	FD_CLR(fd, &(tsdPtr->checkMasks.exceptional));
    }
    if (tsdPtr->numFdBits <= fd) {
	tsdPtr->numFdBits = fd+1;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteFileHandler --
 *
 *	Cancel a previously-arranged callback arrangement for
 *	a file.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If a callback was previously registered on file, remove it.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteFileHandler(fd)
    int fd;		/* Stream id for which to remove callback procedure. */
{
    FileHandler *filePtr, *prevPtr;
    int i;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tclStubs.tcl_DeleteFileHandler != tclOriginalNotifier.deleteFileHandlerProc) {
	tclStubs.tcl_DeleteFileHandler(fd);
	return;
    }

    /*
     * Find the entry for the given file (and return if there isn't one).
     */

    for (prevPtr = NULL, filePtr = tsdPtr->firstFileHandlerPtr; ;
	 prevPtr = filePtr, filePtr = filePtr->nextPtr) {
	if (filePtr == NULL) {
	    return;
	}
	if (filePtr->fd == fd) {
	    break;
	}
    }

    /*
     * Update the check masks for this file.
     */

    if (filePtr->mask & TCL_READABLE) {
	FD_CLR(fd, &(tsdPtr->checkMasks.readable));
    }
    if (filePtr->mask & TCL_WRITABLE) {
	FD_CLR(fd, &(tsdPtr->checkMasks.writable));
    }
    if (filePtr->mask & TCL_EXCEPTION) {
	FD_CLR(fd, &(tsdPtr->checkMasks.exceptional));
    }

    /*
     * Find current max fd.
     */

    if (fd+1 == tsdPtr->numFdBits) {
	tsdPtr->numFdBits = 0;
	for (i = fd-1; i >= 0; i--) {
	    if (FD_ISSET(i, &(tsdPtr->checkMasks.readable))
		    || FD_ISSET(i, &(tsdPtr->checkMasks.writable))
		    || FD_ISSET(i, &(tsdPtr->checkMasks.exceptional))) {
		tsdPtr->numFdBits = i+1;
		break;
	    }
	}
    }

    /*
     * Clean up information in the callback record.
     */

    if (prevPtr == NULL) {
	tsdPtr->firstFileHandlerPtr = filePtr->nextPtr;
    } else {
	prevPtr->nextPtr = filePtr->nextPtr;
    }
    ckfree((char *) filePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * FileHandlerEventProc --
 *
 *	This procedure is called by Tcl_ServiceEvent when a file event
 *	reaches the front of the event queue.  This procedure is
 *	responsible for actually handling the event by invoking the
 *	callback for the file handler.
 *
 * Results:
 *	Returns 1 if the event was handled, meaning it should be removed
 *	from the queue.  Returns 0 if the event was not handled, meaning
 *	it should stay on the queue.  The only time the event isn't
 *	handled is if the TCL_FILE_EVENTS flag bit isn't set.
 *
 * Side effects:
 *	Whatever the file handler's callback procedure does.
 *
 *----------------------------------------------------------------------
 */

static int
FileHandlerEventProc(evPtr, flags)
    Tcl_Event *evPtr;		/* Event to service. */
    int flags;			/* Flags that indicate what events to
				 * handle, such as TCL_FILE_EVENTS. */
{
    int mask;
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr = (FileHandlerEvent *) evPtr;
    ThreadSpecificData *tsdPtr;

    if (!(flags & TCL_FILE_EVENTS)) {
	return 0;
    }

    /*
     * Search through the file handlers to find the one whose handle matches
     * the event.  We do this rather than keeping a pointer to the file
     * handler directly in the event, so that the handler can be deleted
     * while the event is queued without leaving a dangling pointer.
     */

    tsdPtr = TCL_TSD_INIT(&dataKey);
    for (filePtr = tsdPtr->firstFileHandlerPtr; filePtr != NULL;
	    filePtr = filePtr->nextPtr) {
	if (filePtr->fd != fileEvPtr->fd) {
	    continue;
	}

	/*
	 * The code is tricky for two reasons:
	 * 1. The file handler's desired events could have changed
	 *    since the time when the event was queued, so AND the
	 *    ready mask with the desired mask.
	 * 2. The file could have been closed and re-opened since
	 *    the time when the event was queued.  This is why the
	 *    ready mask is stored in the file handler rather than
	 *    the queued event:  it will be zeroed when a new
	 *    file handler is created for the newly opened file.
	 */

	mask = filePtr->readyMask & filePtr->mask;
	filePtr->readyMask = 0;
	if (mask != 0) {
	    (*filePtr->proc)(filePtr->clientData, mask);
	}
	break;
    }
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_WaitForEvent --
 *
 *	This function is called by Tcl_DoOneEvent to wait for new
 *	events on the message queue.  If the block time is 0, then
 *	Tcl_WaitForEvent just polls without blocking.
 *
 * Results:
 *	Returns -1 if the select would block forever, otherwise
 *	returns 0.
 *
 * Side effects:
 *	Queues file events that are detected by the select.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WaitForEvent(timePtr)
    Tcl_Time *timePtr;		/* Maximum block time, or NULL. */
{
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr;
    int mask;
    Tcl_Time myTime;
    int waitForFiles;
    Tcl_Time *myTimePtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tclStubs.tcl_WaitForEvent != tclOriginalNotifier.waitForEventProc) {
	return tclStubs.tcl_WaitForEvent(timePtr);
    }

    if (timePtr != NULL) {
	/* TIP #233 (Virtualized Time). Is virtual time in effect ?
	 * And do we actually have something to scale ? If yes to both
	 * then we call the handler to do this scaling */

	myTime.sec  = timePtr->sec;
	myTime.usec = timePtr->usec;

	if (myTime.sec != 0 || myTime.usec != 0) {
	    (*tclScaleTimeProcPtr) (&myTime, tclTimeClientData);
	}

	myTimePtr = &myTime;
    } else {
	myTimePtr = NULL;
    }

    /*
     * Place this thread on the list of interested threads, signal the
     * notifier thread, and wait for a response or a timeout.
     */

    LOCK_NOTIFIER;

    waitForFiles = (tsdPtr->numFdBits > 0);
    if (myTimePtr != NULL && myTimePtr->sec == 0 && myTimePtr->usec == 0) {
	/*
	 * Cannot emulate a polling select with a polling condition variable.
	 * Instead, pretend to wait for files and tell the notifier
	 * thread what we are doing.  The notifier thread makes sure
	 * it goes through select with its select mask in the same state
	 * as ours currently is.  We block until that happens.
	 */

	waitForFiles = 1;
	tsdPtr->pollState = POLL_WANT;
	myTimePtr = NULL;
    } else {
	tsdPtr->pollState = 0;
    }

    if (waitForFiles) {
	/*
	 * Add the ThreadSpecificData structure of this thread to the list
	 * of ThreadSpecificData structures of all threads that are waiting
	 * on file events.
	 */

	tsdPtr->nextPtr = waitingListPtr;
	if (waitingListPtr) {
	    waitingListPtr->prevPtr = tsdPtr;
	}
	tsdPtr->prevPtr = 0;
	waitingListPtr = tsdPtr;
	tsdPtr->onList = 1;

	write(triggerPipe, "", 1);
    }

    FD_ZERO(&(tsdPtr->readyMasks.readable));
    FD_ZERO(&(tsdPtr->readyMasks.writable));
    FD_ZERO(&(tsdPtr->readyMasks.exceptional));

    if (!tsdPtr->eventReady) {
        CFTimeInterval waitTime;

        if (myTimePtr == NULL) {
            waitTime = 1.0e10; /* Wait forever, as per CFRunLoop.c */
        } else {
            waitTime = myTimePtr->sec + 1.0e-6 * myTimePtr->usec;
        }
        UNLOCK_NOTIFIER;
        CFRunLoopRunInMode(kCFRunLoopDefaultMode, waitTime, TRUE);
        LOCK_NOTIFIER;
    }
    tsdPtr->eventReady = 0;

    if (waitForFiles && tsdPtr->onList) {
	/*
	 * Remove the ThreadSpecificData structure of this thread from the
	 * waiting list.  Alert the notifier thread to recompute its select
	 * masks - skipping this caused a hang when trying to close a pipe
	 * which the notifier thread was still doing a select on.
	 */

	if (tsdPtr->prevPtr) {
	    tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr;
	} else {
	    waitingListPtr = tsdPtr->nextPtr;
	}
	if (tsdPtr->nextPtr) {
	    tsdPtr->nextPtr->prevPtr = tsdPtr->prevPtr;
	}
	tsdPtr->nextPtr = tsdPtr->prevPtr = NULL;
	tsdPtr->onList = 0;
	write(triggerPipe, "", 1);
    }

    
    /*
     * Queue all detected file events before returning.
     */

    for (filePtr = tsdPtr->firstFileHandlerPtr; (filePtr != NULL);
	    filePtr = filePtr->nextPtr) {

	mask = 0;
	if (FD_ISSET(filePtr->fd, &(tsdPtr->readyMasks.readable))) {
	    mask |= TCL_READABLE;
	}
	if (FD_ISSET(filePtr->fd, &(tsdPtr->readyMasks.writable))) {
	    mask |= TCL_WRITABLE;
	}
	if (FD_ISSET(filePtr->fd, &(tsdPtr->readyMasks.exceptional))) {
	    mask |= TCL_EXCEPTION;
	}

	if (!mask) {
	    continue;
	}

	/*
	 * Don't bother to queue an event if the mask was previously
	 * non-zero since an event must still be on the queue.
	 */

	if (filePtr->readyMask == 0) {
	    fileEvPtr = (FileHandlerEvent *) ckalloc(sizeof(FileHandlerEvent));
	    fileEvPtr->header.proc = FileHandlerEventProc;
	    fileEvPtr->fd = filePtr->fd;
	    Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);
	}
	filePtr->readyMask = mask;
    }
    UNLOCK_NOTIFIER;
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * NotifierThreadProc --
 *
 *	This routine is the initial (and only) function executed by the
 *	special notifier thread.  Its job is to wait for file descriptors
 *	to become readable or writable or to have an exception condition
 *	and then to notify other threads who are interested in this
 *	information by signalling a condition variable.  Other threads
 *	can signal this notifier thread of a change in their interests
 *	by writing a single byte to a special pipe that the notifier
 *	thread is monitoring.
 *
 * Result:
 *	None.  Once started, this routine never exits.  It dies with
 *	the overall process.
 *
 * Side effects:
 *	The trigger pipe used to signal the notifier thread is created
 *	when the notifier thread first starts.
 *
 *----------------------------------------------------------------------
 */

static void
NotifierThreadProc(clientData)
    ClientData clientData;	/* Not used. */
{
    ThreadSpecificData *tsdPtr;
    fd_set readableMask;
    fd_set writableMask;
    fd_set exceptionalMask;
    int i, numFdBits = 0;
    long found;
    struct timeval poll = {0., 0.}, *timePtr;
    char buf[2];

    /*
     * Look for file events and report them to interested threads.
     */

    while (1) {
	FD_ZERO(&readableMask);
	FD_ZERO(&writableMask);
	FD_ZERO(&exceptionalMask);

	/*
	 * Compute the logical OR of the select masks from all the
	 * waiting notifiers.
	 */

	LOCK_NOTIFIER;
	timePtr = NULL;
	for (tsdPtr = waitingListPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {
	    for (i = tsdPtr->numFdBits-1; i >= 0; --i) {
		if (FD_ISSET(i, &(tsdPtr->checkMasks.readable))) {
		    FD_SET(i, &readableMask);
		}
		if (FD_ISSET(i, &(tsdPtr->checkMasks.writable))) {
		    FD_SET(i, &writableMask);
		}
		if (FD_ISSET(i, &(tsdPtr->checkMasks.exceptional))) {
		    FD_SET(i, &exceptionalMask);
		}
	    }
	    if (tsdPtr->numFdBits > numFdBits) {
		numFdBits = tsdPtr->numFdBits;
	    }
	    if (tsdPtr->pollState & POLL_WANT) {
		/*
		 * Here we make sure we go through select() with the same
		 * mask bits that were present when the thread tried to poll.
		 */

		tsdPtr->pollState |= POLL_DONE;
		timePtr = &poll;
	    }
	}
	UNLOCK_NOTIFIER;

	/*
	 * Set up the select mask to include the receive pipe.
	 */

	if (receivePipe >= numFdBits) {
	    numFdBits = receivePipe + 1;
	}
	FD_SET(receivePipe, &readableMask);

	if (select(numFdBits, &readableMask, &writableMask, &exceptionalMask,
		timePtr) == -1) {
	    /*
	     * Try again immediately on an error.
	     */

	    continue;
	}

	/*
	 * Alert any threads that are waiting on a ready file descriptor.
	 */

	LOCK_NOTIFIER;
	for (tsdPtr = waitingListPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {
	    found = 0;

	    for (i = tsdPtr->numFdBits-1; i >= 0; --i) {
		if (FD_ISSET(i, &(tsdPtr->checkMasks.readable))
			&& FD_ISSET(i, &readableMask)) {
		    FD_SET(i, &(tsdPtr->readyMasks.readable));
		    found = 1;
		}
		if (FD_ISSET(i, &(tsdPtr->checkMasks.writable))
			&& FD_ISSET(i, &writableMask)) {
		    FD_SET(i, &(tsdPtr->readyMasks.writable));
		    found = 1;
		}
		if (FD_ISSET(i, &(tsdPtr->checkMasks.exceptional))
			&& FD_ISSET(i, &exceptionalMask)) {
		    FD_SET(i, &(tsdPtr->readyMasks.exceptional));
		    found = 1;
		}
	    }

	    if (found || (tsdPtr->pollState & POLL_DONE)) {
		tsdPtr->eventReady = 1;
		if (tsdPtr->onList) {
		    /*
		     * Remove the ThreadSpecificData structure of this
		     * thread from the waiting list. This prevents us from
		     * continuously spining on select until the other
		     * threads runs and services the file event.
		     */

		    if (tsdPtr->prevPtr) {
			tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr;
		    } else {
			waitingListPtr = tsdPtr->nextPtr;
		    }
		    if (tsdPtr->nextPtr) {
			tsdPtr->nextPtr->prevPtr = tsdPtr->prevPtr;
		    }
		    tsdPtr->nextPtr = tsdPtr->prevPtr = NULL;
		    tsdPtr->onList = 0;
		    tsdPtr->pollState = 0;
		}
		if (tsdPtr->runLoop) {
		    CFRunLoopSourceSignal(tsdPtr->runLoopSource);
		    CFRunLoopWakeUp(tsdPtr->runLoop);
		}
	    }
	}
	UNLOCK_NOTIFIER;

	/*
	 * Consume the next byte from the notifier pipe if the pipe was
	 * readable.  Note that there may be multiple bytes pending, but
	 * to avoid a race condition we only read one at a time.
	 */

	if (FD_ISSET(receivePipe, &readableMask)) {
	    i = read(receivePipe, buf, 1);

	    if ((i == 0) || ((i == 1) && (buf[0] == 'q'))) {
		/*
		 * Someone closed the write end of the pipe or sent us a
		 * Quit message [Bug: 4139] and then closed the write end
		 * of the pipe so we need to shut down the notifier thread.
		 */

		break;
	    }
	}
    }
    pthread_exit (0);
}

#endif /* HAVE_COREFOUNDATION */