/*
* 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 1.34.2.2 2010/01/29 09:38:47 nijtmans 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 writing to the pipe.
*/
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(¬ifierMutex);
if (notifierCount == 0) {
if (TclpThreadCreate(¬ifierThread, 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(¬ifierCV, ¬ifierMutex, NULL);
}
Tcl_MutexUnlock(¬ifierMutex);
#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(¬ifierMutex);
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]
*/
if (write(triggerPipe, "q", 1) != 1) {
Tcl_Panic("Tcl_FinalizeNotifier: unable to write q to triggerPipe");
}
close(triggerPipe);
while(triggerPipe >= 0) {
Tcl_ConditionWait(¬ifierCV, ¬ifierMutex, 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(¬ifierMutex);
#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(¬ifierMutex);
tsdPtr->eventReady = 1;
Tcl_ConditionNotify(&tsdPtr->waitCV);
Tcl_MutexUnlock(¬ifierMutex);
#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) {
int 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))) {
numFdBits = i+1;
break;
}
}
tsdPtr->numFdBits = numFdBits;
}
/*
* 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 vTime;
#ifdef TCL_THREADS
int waitForFiles;
#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.
*/
if (timePtr->sec != 0 || timePtr->usec != 0) {
vTime = *timePtr;
(*tclScaleTimeProcPtr) (&vTime, tclTimeClientData);
timePtr = &vTime;
}
#ifndef TCL_THREADS
timeout.tv_sec = timePtr->sec;
timeout.tv_usec = timePtr->usec;
timeoutPtr = &timeout;
} 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;
} 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(¬ifierMutex);
if (timePtr != NULL && timePtr->sec == 0 && (timePtr->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]
*/
|| timePtr->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;
timePtr = NULL;
} else {
waitForFiles = (tsdPtr->numFdBits > 0);
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;
if (write(triggerPipe, "", 1) != 1) {
Tcl_Panic("Tcl_WaitForEvent: unable to write to triggerPipe");
}
}
FD_ZERO(&(tsdPtr->readyMasks.readable));
FD_ZERO(&(tsdPtr->readyMasks.writable));
FD_ZERO(&(tsdPtr->readyMasks.exceptional));
if (!tsdPtr->eventReady) {
Tcl_ConditionWait(&tsdPtr->waitCV, ¬ifierMutex, timePtr);
}
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;
if (write(triggerPipe, "", 1) != 1) {
Tcl_Panic("Tcl_WaitForEvent: unable to write to triggerPipe");
}
}
#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(¬ifierMutex);
#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(¬ifierMutex);
triggerPipe = fds[1];
/*
* Signal any threads that are waiting.
*/
Tcl_ConditionNotify(¬ifierCV);
Tcl_MutexUnlock(¬ifierMutex);
/*
* 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(¬ifierMutex);
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(¬ifierMutex);
/*
* 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(¬ifierMutex);
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(¬ifierMutex);
/*
* 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(¬ifierMutex);
triggerPipe = -1;
Tcl_ConditionNotify(¬ifierCV);
Tcl_MutexUnlock(¬ifierMutex);
TclpThreadExit (0);
}
#endif /* TCL_THREADS */
#endif /* HAVE_COREFOUNDATION */
/*
* Local Variables:
* mode: c
* c-basic-offset: 4
* fill-column: 78
* End:
*/
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