path: root/unix/tclEpollNotfy.c

/*
 * tclEpollNotfy.c --
 *
 *	This file contains the implementation of the epoll()-based
 *	Linux-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.
 * Copyright (c) 2016 Lucio Andrés Illanes Albornoz <l.illanes@gmx.de>
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

#ifdef NOTIFIER_EPOLL

#define _GNU_SOURCE		/* For pipe2(2) */
#include "tclInt.h"
#ifndef HAVE_COREFOUNDATION	/* Darwin/Mac OS X CoreFoundation notifier is
				 * in tclMacOSXNotify.c */
#include <fcntl.h>
#include <signal.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>
#include <sys/queue.h>
#include <unistd.h>

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

struct PlatformEventData;
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. */
    LIST_ENTRY(FileHandler) readyNode;
				/* Next/previous in list of FileHandlers asso-
				 * ciated with regular files (S_IFREG) that are
				 * ready for I/O. */
    struct PlatformEventData *pedPtr;
				/* Pointer to PlatformEventData associating this
				 * FileHandler with epoll(7) events. */
} FileHandler;

/*
 * The following structure associates a FileHandler and the thread that owns it
 * with the file descriptors of interest and their event masks passed to epoll_ctl(2)
 * and their corresponding event(s) returned by epoll_wait(2).
 */

struct ThreadSpecificData;
struct PlatformEventData {
    FileHandler *filePtr;
    struct ThreadSpecificData *tsdPtr;
};

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

typedef struct {
    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 static structure contains the state information for the
 * epoll based implementation of the Tcl notifier. One of these structures is
 * created for each thread that is using the notifier.
 */

LIST_HEAD(PlatformReadyFileHandlerList, FileHandler);
typedef struct ThreadSpecificData {
    FileHandler *firstFileHandlerPtr;
				/* Pointer to head of file handler list. */
    struct PlatformReadyFileHandlerList firstReadyFileHandlerPtr;
				/* Pointer to head of list of FileHandlers
				 * associated with regular files (S_IFREG)
				 * that are ready for I/O. */
    pthread_mutex_t notifierMutex;
				/* Mutex protecting notifier termination in
				 * PlatformEventsFinalize. */
#ifdef HAVE_EVENTFD
    int triggerEventFd;		/* eventfd(2) used by other threads to wake
				 * up this thread for inter-thread IPC. */
#else
    int triggerPipe[2];		/* pipe(2) used by other threads to wake
				 * up this thread for inter-thread IPC. */
#endif /* HAVE_EVENTFD */
    int eventsFd;		/* epoll(7) file descriptor used to wait for fds */
    struct epoll_event *readyEvents;
				/* Pointer to at most maxReadyEvents events
				 * returned by epoll_wait(2). */
    size_t maxReadyEvents;	/* Count of epoll_events in readyEvents. */
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

void PlatformEventsControl(FileHandler *filePtr, ThreadSpecificData *tsdPtr, int op, int isNew);
static void PlatformEventsFinalize(void);
void PlatformEventsInit(void);
static int PlatformEventsTranslate(struct epoll_event *event);
static int PlatformEventsWait(struct epoll_event *events, size_t numEvents, struct timeval *timePtr);

#include "tclUnixNotfy.c"

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InitNotifier --
 *
 *	Initializes the platform specific notifier state.
 *
 * Results:
 *	Returns a handle to the notifier state for this thread.
 *
 * Side effects:
 *	If no initNotifierProc notifier hook exists, PlatformEventsInit
 *	is called.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_InitNotifier(void)
{
    if (tclNotifierHooks.initNotifierProc) {
	return tclNotifierHooks.initNotifierProc();
    } else {
	ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

	PlatformEventsInit();
	return tsdPtr;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FinalizeNotifier --
 *
 *	This function is called to cleanup the notifier state before a thread
 *	is terminated.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If no finalizeNotifierProc notifier hook exists, PlatformEvents-
 *	Finalize is called.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_FinalizeNotifier(
    ClientData clientData)		/* Not used. */
{
    if (tclNotifierHooks.finalizeNotifierProc) {
	tclNotifierHooks.finalizeNotifierProc(clientData);
	return;
    } else {
	PlatformEventsFinalize();
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PlatformEventsControl --
 *
 *	This function registers interest for the file descriptor and the mask
 *	of TCL_* bits associated with filePtr on the epoll file descriptor
 *	associated with tsdPtr.
 *	Future calls to epoll_wait will return filePtr and tsdPtr alongside with
 *	the event registered here via the PlatformEventData struct.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If adding a new file descriptor, a PlatformEventData struct will be
 *	allocated and associated with filePtr.
 *	fstat is called on the file descriptor; if it is associated with
 *	a regular file (S_IFREG,) filePtr is considered to be ready for I/O
 *	and added to or deleted from the corresponding list in tsdPtr.
 *	If it is not associated with a regular file, the file descriptor is
 *	added, modified concerning its mask of events of interest, or deleted
 *	from the epoll file descriptor of the calling thread.
 *
 *----------------------------------------------------------------------
 */

void
PlatformEventsControl(
	FileHandler *filePtr,
	ThreadSpecificData *tsdPtr,
	int op,
	int isNew)
{
    struct epoll_event newEvent;
    struct PlatformEventData *newPedPtr;
    struct stat fdStat;

    newEvent.events = 0;
    if (filePtr->mask & (TCL_READABLE | TCL_EXCEPTION)) {
	newEvent.events |= EPOLLIN;
    }
    if (filePtr->mask & TCL_WRITABLE) {
	newEvent.events |= EPOLLOUT;
    }
    if (isNew) {
        newPedPtr = ckalloc(sizeof(*newPedPtr));
        newPedPtr->filePtr = filePtr;
        newPedPtr->tsdPtr = tsdPtr;
	filePtr->pedPtr = newPedPtr;
    }
    newEvent.data.ptr = filePtr->pedPtr;

    /*
     * N.B.	As discussed in Tcl_WaitForEvent(), epoll(7) does not sup-
     *		port regular files (S_IFREG.) Therefore, filePtr is in these
     *		cases simply added or deleted from the list of FileHandlers
     *		associated with regular files belonging to tsdPtr.
     */

    if (fstat(filePtr->fd, &fdStat) == -1) {
	Tcl_Panic("fstat: %s", strerror(errno));
    } else if ((fdStat.st_mode & S_IFMT) == S_IFREG) {
	switch (op) {
	case EPOLL_CTL_ADD:
	    if (isNew) {
		LIST_INSERT_HEAD(&tsdPtr->firstReadyFileHandlerPtr, filePtr, readyNode);
	    }
	    break;
	case EPOLL_CTL_DEL:
	    LIST_REMOVE(filePtr, readyNode);
	    break;
	}
	return;
   } else if (epoll_ctl(tsdPtr->eventsFd, op, filePtr->fd, &newEvent) == -1) {
	Tcl_Panic("epoll_ctl: %s", strerror(errno));
   }
}

/*
 *----------------------------------------------------------------------
 *
 * PlatformEventsFinalize --
 *
 *	This function closes the eventfd and the epoll file descriptor and
 *	frees the epoll_event structs owned by the thread of the caller.
 *	The above operations are protected by tsdPtr->notifierMutex, which
 *	is destroyed thereafter.
 *
 * Results:
 *	None.
 *
 * Side effects:
 * 	While tsdPtr->notifierMutex is held:
 *	The per-thread eventfd(2) is closed, if non-zero, and set to -1.
 *	The per-thread epoll(7) fd is closed, if non-zero, and set to 0.
 *	The per-thread epoll_event structs are freed, if any, and set to 0.
 *
 *	tsdPtr->notifierMutex is destroyed.
 *
 *----------------------------------------------------------------------
 */

void
PlatformEventsFinalize(
	void)
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    pthread_mutex_lock(&tsdPtr->notifierMutex);
#ifdef HAVE_EVENTFD
    if (tsdPtr->triggerEventFd) {
	close(tsdPtr->triggerEventFd);
	tsdPtr->triggerEventFd = -1;
    }
#else
    if (tsdPtr->triggerPipe[0]) {
	close(tsdPtr->triggerPipe[0]);
	tsdPtr->triggerPipe[0] = -1;
    }
    if (tsdPtr->triggerPipe[1]) {
	close(tsdPtr->triggerPipe[1]);
	tsdPtr->triggerPipe[1] = -1;
    }
#endif /* HAVE_EVENTFD */
    if (tsdPtr->eventsFd > 0) {
	close(tsdPtr->eventsFd);
	tsdPtr->eventsFd = 0;
    }
    if (tsdPtr->readyEvents) {
	ckfree(tsdPtr->readyEvents);
	tsdPtr->maxReadyEvents = 0;
    }
    pthread_mutex_unlock(&tsdPtr->notifierMutex);
    if ((errno = pthread_mutex_destroy(&tsdPtr->notifierMutex))) {
	Tcl_Panic("pthread_mutex_destroy: %s", strerror(errno));
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PlatformEventsInit --
 *
 *	This function abstracts creating a kqueue fd via the epoll_create
 *	system call and allocating memory for the epoll_event structs in
 *	tsdPtr for the thread of the caller.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The following per-thread entities are initialised:
 *	notifierMutex is initialised.
 *	The eventfd(2) is created w/ EFD_CLOEXEC and EFD_NONBLOCK.
 *	The epoll(7) fd is created w/ EPOLL_CLOEXEC.
 *	A FileHandler struct is allocated and initialised for the event-
 *	fd(2), registering interest for TCL_READABLE on it via Platform-
 *	EventsControl().
 *	readyEvents and maxReadyEvents are initialised with 512 epoll_events.
 *
 *----------------------------------------------------------------------
 */

void
PlatformEventsInit(
	void)
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    FileHandler *filePtr;

    errno = pthread_mutex_init(&tsdPtr->notifierMutex, NULL);
    if (errno) {
	Tcl_Panic("Tcl_InitNotifier: %s", "could not create mutex");
    }
    filePtr = ckalloc(sizeof(*filePtr));
#ifdef HAVE_EVENTFD
    if ((tsdPtr->triggerEventFd = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK)) <= 0) {
	Tcl_Panic("Tcl_InitNotifier: %s", "could not create trigger eventfd");
    }
    filePtr->fd = tsdPtr->triggerEventFd;
#else
    if (pipe2(tsdPtr->triggerPipe, O_CLOEXEC | O_NONBLOCK) != 0) {
	Tcl_Panic("Tcl_InitNotifier: %s", "could not create trigger pipe");
    }
    filePtr->fd = tsdPtr->triggerPipe[0];
#endif
    if ((tsdPtr->eventsFd = epoll_create1(EPOLL_CLOEXEC)) == -1) {
	Tcl_Panic("epoll_create1: %s", strerror(errno));
    }
    filePtr->mask = TCL_READABLE;
    PlatformEventsControl(filePtr, tsdPtr, EPOLL_CTL_ADD, 1);
    if (!tsdPtr->readyEvents) {
        tsdPtr->maxReadyEvents = 512;
	tsdPtr->readyEvents = ckalloc(tsdPtr->maxReadyEvents
	    * sizeof(tsdPtr->readyEvents[0]));
    }
    LIST_INIT(&tsdPtr->firstReadyFileHandlerPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * PlatformEventsTranslate --
 *
 *	This function translates the platform-specific mask of returned
 *	events in eventPtr to a mask of TCL_* bits.
 *
 * Results:
 *	Returns the translated mask.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
PlatformEventsTranslate(
	struct epoll_event *eventPtr)
{
    int mask;

    mask = 0;
    if (eventPtr->events & (EPOLLIN | EPOLLHUP)) {
	mask |= TCL_READABLE;
    }
    if (eventPtr->events & EPOLLOUT) {
	mask |= TCL_WRITABLE;
    }
    if (eventPtr->events & EPOLLERR) {
	mask |= TCL_EXCEPTION;
    }
    return mask;
}

/*
 *----------------------------------------------------------------------
 *
 * PlatformEventsWait --
 *
 *	This function abstracts waiting for I/O events via epoll_wait.
 *
 * Results:
 *	Returns -1 if epoll_wait failed. Returns 0 if polling and if no
 *	events became available whilst polling. Returns a pointer to and
 *	the count of all returned events in all other cases.
 *
 * Side effects:
 *	gettimeofday(2), epoll_wait(2), and gettimeofday(2) are called,
 *	in the specified order.
 *	If timePtr specifies a positive value, it is updated to reflect
 *	the amount of time that has passed; if its value would {under,
 *	over}flow, it is set to zero.
 *
 *----------------------------------------------------------------------
 */

int
PlatformEventsWait(
    struct epoll_event *events,
    size_t numEvents,
    struct timeval *timePtr)
{
    int numFound;
    struct timeval tv0, tv1, tv_delta;
    int timeout;

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * If timePtr is NULL, epoll_wait(2) will wait indefinitely. If it
     * specifies a timeout of {0,0}, epoll_wait(2) will poll. Otherwise,
     * the timeout will simply be converted to milliseconds.
     */

    if (!timePtr) {
	timeout = -1;
    } else if (!timePtr->tv_sec && !timePtr->tv_usec) {
	timeout = 0;
    } else {
	timeout = (int)timePtr->tv_sec;
    }

    /*
     * Call (and possibly block on) epoll_wait(2) and substract the delta
     * of gettimeofday(2) before and after the call from timePtr if the
     * latter is not NULL. Return the number of events returned by epoll_wait(2).
     */

    gettimeofday(&tv0, NULL);
    numFound = epoll_wait(tsdPtr->eventsFd, events, (int)numEvents, timeout);
    gettimeofday(&tv1, NULL);
    if (timePtr && (timePtr->tv_sec && timePtr->tv_usec)) {
	timersub(&tv1, &tv0, &tv_delta);
	if (!timercmp(&tv_delta, timePtr, >)) {
		timersub(timePtr, &tv_delta, timePtr);
	} else {
		timePtr->tv_sec = 0;
		timePtr->tv_usec = 0;
	}
    }
    return numFound;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateFileHandler --
 *
 *	This function registers a file handler with the epoll notifier
 *	of the thread of the caller.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new file handler structure.
 *	PlatformEventsControl() is called for the 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. */
{
    int isNew;

    if (tclNotifierHooks.createFileHandlerProc) {
	tclNotifierHooks.createFileHandlerProc(fd, mask, proc, clientData);
	return;
    } else {
	ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
	FileHandler *filePtr;

	for (filePtr = tsdPtr->firstFileHandlerPtr; filePtr != NULL;
		filePtr = filePtr->nextPtr) {
	    if (filePtr->fd == fd) {
		break;
	    }
	}
	if (filePtr == NULL) {
	    filePtr = ckalloc(sizeof(FileHandler));
	    filePtr->fd = fd;
	    filePtr->readyMask = 0;
	    filePtr->nextPtr = tsdPtr->firstFileHandlerPtr;
	    tsdPtr->firstFileHandlerPtr = filePtr;
	    isNew = 1;
	} else {
	    isNew = 0;
	}
	filePtr->proc = proc;
	filePtr->clientData = clientData;
	filePtr->mask = mask;

	PlatformEventsControl(filePtr, tsdPtr, isNew ?
	    EPOLL_CTL_ADD : EPOLL_CTL_MOD, isNew);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteFileHandler --
 *
 *	Cancel a previously-arranged callback arrangement for a file on
 *	the epoll file descriptor of the thread of the caller.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If a callback was previously registered on file, remove it.
 *	PlatformEventsControl() is called for the file handler structure.
 *	The PlatformEventData struct associated with the new file handler
 *	structure is freed.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteFileHandler(
    int fd)			/* Stream id for which to remove callback
				 * function. */
{
    if (tclNotifierHooks.deleteFileHandlerProc) {
	tclNotifierHooks.deleteFileHandlerProc(fd);
	return;
    } else {
	FileHandler *filePtr, *prevPtr;
	ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

	/*
	 * 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.
	 */

	PlatformEventsControl(filePtr, tsdPtr, EPOLL_CTL_DEL, 0);
	if (filePtr->pedPtr) {
	    ckfree(filePtr->pedPtr);
	}

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

	if (prevPtr == NULL) {
	    tsdPtr->firstFileHandlerPtr = filePtr->nextPtr;
	} else {
	    prevPtr->nextPtr = filePtr->nextPtr;
	}
	ckfree(filePtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * 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.
 *	The waiting logic is implemented in PlatformEventsWait.
 *
 * Results:
 *	Returns -1 if PlatformEventsWait() would block forever, otherwise
 *	returns 0.
 *
 * Side effects:
 *	Queues file events that are detected by PlatformEventsWait().
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WaitForEvent(
    const Tcl_Time *timePtr)		/* Maximum block time, or NULL. */
{
    if (tclNotifierHooks.waitForEventProc) {
	return tclNotifierHooks.waitForEventProc(timePtr);
    } else {
	FileHandler *filePtr;
	int mask;
	Tcl_Time vTime;
	/*
	 * Impl. notes: timeout & timeoutPtr are used if, and only if threads
	 * are not enabled. They are the arguments for the regular epoll_wait()
	 * used when the core is not thread-enabled.
	 */

	struct timeval timeout, *timeoutPtr;
	int numFound, numEvent;
	struct PlatformEventData *pedPtr;
	ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
	int numQueued;
	ssize_t i;

	/*
	 * 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.
	     */

	    if (timePtr->sec != 0 || timePtr->usec != 0) {
		vTime = *timePtr;
		tclScaleTimeProcPtr(&vTime, tclTimeClientData);
		timePtr = &vTime;
	    }
	    timeout.tv_sec = timePtr->sec;
	    timeout.tv_usec = timePtr->usec;
	    timeoutPtr = &timeout;
	} else {
	    timeoutPtr = NULL;
	}

	/*
	 * Walk the list of FileHandlers associated with regular files
	 * (S_IFREG) belonging to tsdPtr, queue Tcl events for them, and
	 * update their mask of events of interest.
	 * As epoll(7) does not support regular files, the behaviour of
	 * {select,poll}(2) is simply simulated here: fds associated with
	 * regular files are added to this list by PlatformEventsControl()
	 * and processed here before calling (and possibly blocking) on
	 * PlatformEventsWait().
	 */

	numQueued = 0;
	LIST_FOREACH(filePtr, &tsdPtr->firstReadyFileHandlerPtr, readyNode) {
	    mask = 0;
	    if (filePtr->mask & TCL_READABLE) {
		mask |= TCL_READABLE;
	    }
	    if (filePtr->mask & TCL_WRITABLE) {
		mask |= TCL_WRITABLE;
	    }

	    /*
	     * 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) {
		FileHandlerEvent *fileEvPtr =
		    ckalloc(sizeof(FileHandlerEvent));

		fileEvPtr->header.proc = FileHandlerEventProc;
		fileEvPtr->fd = filePtr->fd;
		Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);
		numQueued++;
	    }
	    filePtr->readyMask = mask;
	}

	/*
	 * If any events were queued in the above loop, force PlatformEvents-
	 * Wait() to poll as there already are events that need to be processed
	 * at this point.
	 */

	if (numQueued) {
	    timeout.tv_sec = 0;
	    timeout.tv_usec = 0;
	    timeoutPtr = &timeout;
	}

	/*
	 * Wait or poll for new events, queue Tcl events for the FileHandlers
	 * corresponding to them, and update the FileHandlers' mask of events
	 * of interest registered by the last call to Tcl_CreateFileHandler().
	 *
	 * Events for the eventfd(2)/trigger pipe are processed here in order
	 * to facilitate inter-thread IPC. If another thread intends to wake
	 * up this thread whilst it's blocking on PlatformEventsWait(), it
	 * write(2)s to the eventfd(2)/trigger pipe (see Tcl_AlertNotifier(),)
	 * which in turn will cause PlatformEventsWait() to return immediately.
	 */

	numFound = PlatformEventsWait(tsdPtr->readyEvents, tsdPtr->maxReadyEvents, timeoutPtr);
	for (numEvent = 0; numEvent < numFound; numEvent++) {
	    pedPtr = tsdPtr->readyEvents[numEvent].data.ptr;
	    filePtr = pedPtr->filePtr;
	    mask = PlatformEventsTranslate(&tsdPtr->readyEvents[numEvent]);
#ifdef HAVE_EVENTFD
	    if (filePtr->fd == tsdPtr->triggerEventFd) {
		uint64_t eventFdVal;
		i = read(tsdPtr->triggerEventFd, &eventFdVal, sizeof(eventFdVal));
		if ((i != sizeof(eventFdVal)) && (errno != EAGAIN)) {
#else
	    if (filePtr->fd == tsdPtr->triggerPipe[0]) {
		char triggerPipeVal;
		i = read(tsdPtr->triggerPipe[0], &triggerPipeVal, sizeof(triggerPipeVal));
		if ((i != sizeof(triggerPipeVal)) && (errno != EAGAIN)) {
#endif
			Tcl_Panic("Tcl_WaitForEvent: "
				"read from %p->triggerEventFd: %s",
				(void *)tsdPtr, strerror(errno));
		} else {
		    continue;
		}
	    }
	    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) {
		FileHandlerEvent *fileEvPtr =
			ckalloc(sizeof(FileHandlerEvent));

		fileEvPtr->header.proc = FileHandlerEventProc;
		fileEvPtr->fd = filePtr->fd;
		Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);
	    }
	    filePtr->readyMask = mask;
	}
	return 0;
    }
}

#endif /* !HAVE_COREFOUNDATION */

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