source: downloads/tcl8.5.2/unix/tclUnixNotfy.c @ 25

/*
 * tclUnixNotify.c --
 *
 *      This file contains the implementation of the select()-based
 *      Unix-specific 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.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclUnixNotfy.c,v 1.34 2008/03/11 22:23:50 das Exp $
 */

#include "tclInt.h"
#ifndef HAVE_COREFOUNDATION     /* Darwin/Mac OS X CoreFoundation notifier is
                                 * in tclMacOSXNotify.c */
#include <signal.h>

/*
 * This code does deep stub magic to allow replacement of the notifier at
 * runtime.
 */

extern TclStubs tclStubs;
extern Tcl_NotifierProcs tclOriginalNotifier;

/*
 * This structure is used to keep track of the notifier info for 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;         /* Function 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). */
#ifdef TCL_THREADS
    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
                                 * notifierMutex lock before accessing these
                                 * fields. */
    Tcl_Condition waitCV;       /* Any other thread alerts a notifier that an
                                 * event is ready to be processed by signaling
                                 * this condition variable. */
    int eventReady;             /* True if an event is ready to be processed.
                                 * Used as condition flag together with waitCV
                                 * above. */
#endif
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

#ifdef TCL_THREADS
/*
 * The following static indicates the number of threads that have initialized
 * notifiers.
 *
 * You must hold the notifierMutex lock before accessing this variable.
 */

static int notifierCount = 0;

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

static int triggerPipe = -1;

/*
 * The notifierMutex locks access to all of the global notifier state.
 */

TCL_DECLARE_MUTEX(notifierMutex)

/*
 * The notifier thread signals the notifierCV when it has finished
 * initializing the triggerPipe and right before the notifier thread
 * terminates.
 */

static Tcl_Condition notifierCV;

/*
 * 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 Tcl_ThreadId notifierThread;

#endif

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

#ifdef TCL_THREADS
static void     NotifierThreadProc(ClientData clientData);
#endif
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(void)
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

#ifdef TCL_THREADS
    tsdPtr->eventReady = 0;

    /*
     * Start the Notifier thread if necessary.
     */

    Tcl_MutexLock(&notifierMutex);
    if (notifierCount == 0) {
        if (TclpThreadCreate(&notifierThread, NotifierThreadProc, NULL,
                TCL_THREAD_STACK_DEFAULT, TCL_THREAD_JOINABLE) != TCL_OK) {
            Tcl_Panic("Tcl_InitNotifier: unable to start notifier thread");
        }
    }
    notifierCount++;

    /*
     * Wait for the notifier pipe to be created.
     */

    while (triggerPipe < 0) {
        Tcl_ConditionWait(&notifierCV, &notifierMutex, NULL);
    }

    Tcl_MutexUnlock(&notifierMutex);
#endif
    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)              /* Not used. */
{
#ifdef TCL_THREADS
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    Tcl_MutexLock(&notifierMutex);
    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] [Bug: 1222872]
         */

        write(triggerPipe, "q", 1);
        close(triggerPipe);
        while(triggerPipe >= 0) {
            Tcl_ConditionWait(&notifierCV, &notifierMutex, NULL);
        }

        result = Tcl_JoinThread(notifierThread, NULL);
        if (result) {
            Tcl_Panic("Tcl_FinalizeNotifier: unable to join notifier thread");
        }
    }

    /*
     * Clean up any synchronization objects in the thread local storage.
     */

    Tcl_ConditionFinalize(&(tsdPtr->waitCV));

    Tcl_MutexUnlock(&notifierMutex);
#endif
}

/*
 *----------------------------------------------------------------------
 *
 * 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)
{
#ifdef TCL_THREADS
    ThreadSpecificData *tsdPtr = (ThreadSpecificData *) clientData;
    Tcl_MutexLock(&notifierMutex);
    tsdPtr->eventReady = 1;
    Tcl_ConditionNotify(&tsdPtr->waitCV);
    Tcl_MutexUnlock(&notifierMutex);
#endif
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetTimer --
 *
 *      This function 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(
    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(
    int mode)                   /* Either TCL_SERVICE_ALL, or
                                 * TCL_SERVICE_NONE. */
{
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateFileHandler --
 *
 *      This function registers a file handler with the select notifier.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Creates a new file handler structure.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateFileHandler(
    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,         /* Function 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(
    int fd)                     /* Stream id for which to remove callback
                                 * function. */
{
    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 function is called by Tcl_ServiceEvent when a file event reaches
 *      the front of the event queue. This function 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 function does.
 *
 *----------------------------------------------------------------------
 */

static int
FileHandlerEventProc(
    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(
    Tcl_Time *timePtr)          /* Maximum block time, or NULL. */
{
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr;
    int mask;
    Tcl_Time myTime;
#ifdef TCL_THREADS
    int waitForFiles;
    Tcl_Time *myTimePtr;
#else
    /*
     * Impl. notes: timeout & timeoutPtr are used if, and only if threads are
     * not enabled. They are the arguments for the regular select() used when
     * the core is not thread-enabled.
     */

    struct timeval timeout, *timeoutPtr;
    int numFound;
#endif /* TCL_THREADS */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

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

    /*
     * Set up the timeout structure. Note that if there are no events to check
     * for, we return with a negative result rather than blocking forever.
     */

    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);
        }

#ifdef TCL_THREADS
        myTimePtr = &myTime;
#else
        timeout.tv_sec = myTime.sec;
        timeout.tv_usec = myTime.usec;
        timeoutPtr = &timeout;
#endif /* TCL_THREADS */

#ifndef TCL_THREADS
    } else if (tsdPtr->numFdBits == 0) {
        /*
         * If there are no threads, no timeout, and no fds registered, then
         * there are no events possible and we must avoid deadlock. Note that
         * this is not entirely correct because there might be a signal that
         * could interrupt the select call, but we don't handle that case if
         * we aren't using threads.
         */

        return -1;
#endif /* !TCL_THREADS */
    } else {
#ifdef TCL_THREADS
        myTimePtr = NULL;
#else
        timeoutPtr = NULL;
#endif /* TCL_THREADS */
    }

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

    Tcl_MutexLock(&notifierMutex);

    waitForFiles = (tsdPtr->numFdBits > 0);
    if (myTimePtr != NULL && myTimePtr->sec == 0 && (myTimePtr->usec == 0
#if defined(__APPLE__) && defined(__LP64__)
            /*
             * On 64-bit Darwin, pthread_cond_timedwait() appears to have a bug
             * that causes it to wait forever when passed an absolute time which
             * has already been exceeded by the system time; as a workaround,
             * when given a very brief timeout, just do a poll. [Bug 1457797]
             */
            || myTimePtr->usec < 10
#endif
            )) {
        /*
         * 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) {
        Tcl_ConditionWait(&tsdPtr->waitCV, &notifierMutex, myTimePtr);
    }
    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);
    }

#else
    tsdPtr->readyMasks = tsdPtr->checkMasks;
    numFound = select(tsdPtr->numFdBits, &(tsdPtr->readyMasks.readable),
            &(tsdPtr->readyMasks.writable), &(tsdPtr->readyMasks.exceptional),
            timeoutPtr);

    /*
     * Some systems don't clear the masks after an error, so we have to do it
     * here.
     */

    if (numFound == -1) {
        FD_ZERO(&(tsdPtr->readyMasks.readable));
        FD_ZERO(&(tsdPtr->readyMasks.writable));
        FD_ZERO(&(tsdPtr->readyMasks.exceptional));
    }
#endif /* TCL_THREADS */

    /*
     * 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;
    }
#ifdef TCL_THREADS
    Tcl_MutexUnlock(&notifierMutex);
#endif /* TCL_THREADS */
    return 0;
}

#ifdef TCL_THREADS
/*
 *----------------------------------------------------------------------
 *
 * 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)      /* Not used. */
{
    ThreadSpecificData *tsdPtr;
    fd_set readableMask;
    fd_set writableMask;
    fd_set exceptionalMask;
    int fds[2];
    int i, numFdBits = 0, receivePipe;
    long found;
    struct timeval poll = {0., 0.}, *timePtr;
    char buf[2];

    if (pipe(fds) != 0) {
        Tcl_Panic("NotifierThreadProc: could not create trigger pipe");
    }

    receivePipe = fds[0];

    if (TclUnixSetBlockingMode(receivePipe, TCL_MODE_NONBLOCKING) < 0) {
        Tcl_Panic("NotifierThreadProc: could not make receive pipe non blocking");
    }
    if (TclUnixSetBlockingMode(fds[1], TCL_MODE_NONBLOCKING) < 0) {
        Tcl_Panic("NotifierThreadProc: could not make trigger pipe non blocking");
    }

    /*
     * Install the write end of the pipe into the global variable.
     */

    Tcl_MutexLock(&notifierMutex);
    triggerPipe = fds[1];

    /*
     * Signal any threads that are waiting.
     */

    Tcl_ConditionNotify(&notifierCV);
    Tcl_MutexUnlock(&notifierMutex);

    /*
     * 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.
         */

        Tcl_MutexLock(&notifierMutex);
        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;
            }
        }
        Tcl_MutexUnlock(&notifierMutex);

        /*
         * 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.
         */

        Tcl_MutexLock(&notifierMutex);
        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;
                }
                Tcl_ConditionNotify(&tsdPtr->waitCV);
            }
        }
        Tcl_MutexUnlock(&notifierMutex);

        /*
         * 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;
            }
        }
    }

    /*
     * Clean up the read end of the pipe and signal any threads waiting on
     * termination of the notifier thread.
     */

    close(receivePipe);
    Tcl_MutexLock(&notifierMutex);
    triggerPipe = -1;
    Tcl_ConditionNotify(&notifierCV);
    Tcl_MutexUnlock(&notifierMutex);

    TclpThreadExit (0);
}
#endif /* TCL_THREADS */

#endif /* HAVE_COREFOUNDATION */

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */