Tcl Source Code

Check-in [87deb82e27]
Login
Bounty program for improvements to Tcl and certain Tcl packages.

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Reimplemented Tcl_ConditionNotify and Tcl_ConditionWait based on an algorithm contributed by Jim Davidson.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | core-8-1-branch-old
Files: files | file ages | folders
SHA1: 87deb82e27548abdf5aae8a7f5a917868a8d7e90
User & Date: welch 1999-04-01 23:25:19
Context
1999-04-02
00:54
Fix previous patch on Solaris, need to provide the Tcl package before calling Tcl_InitStubs(). check-in: c8e8856000 user: redman tags: core-8-1-branch-old
1999-04-01
23:25
Reimplemented Tcl_ConditionNotify and Tcl_ConditionWait based on an algorithm contributed by Jim Dav... check-in: 87deb82e27 user: welch tags: core-8-1-branch-old
23:23
Deleted unused code. check-in: e6c75f634f user: welch tags: core-8-1-branch-old
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to win/tclWinThrd.c.

1
2
3
4
5
6

7
8
9
10
11
12
13
..
32
33
34
35
36
37
38
39









40
41
42
43






































44
45
46
47
48
49
50
...
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
...
574
575
576
577
578
579
580
581
582
583
584
585
586
587



588












































589
590
591
592
593
594

595
596
597
598
599
600

601
602
603
604
605
606
607
608
609
610
611
612
613
614
615

616
617
618


619




620




621
622
623
624







625
626





627

628



629
630
631
632


633
634
635
636




637
638
639




640
641
642
















643
644
645
646
647
648
649
...
662
663
664
665
666
667
668
669

670
671

672
673
674
675
676
677
678
679
680
681


682







683


684
685
686
687
688
689
690



























691
692
693
694
695
696
697
...
708
709
710
711
712
713
714
715








716
717
718
719
720
721
722
723
724
/* 
 * tclWinThread.c --
 *
 *	This file implements the Windows-specific thread operations.
 *
 * Copyright (c) 1998 by Sun Microsystems, Inc.

 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * SCCS:  @(#) tclWinThrd.c 1.13 98/02/18 14:00:23
 */

................................................................................
 * This is the master lock used to serialize initialization and finalization
 * of Tcl as a whole.
 */

static CRITICAL_SECTION initLock;

/*
 * This is a preallocated lock for use by memory allocators.









 */

static CRITICAL_SECTION allocLock;
TCL_DECLARE_MUTEX(allocMutex)







































 
/*
 *----------------------------------------------------------------------
 *
 * TclpThreadCreate --
 *
................................................................................
 *
 *----------------------------------------------------------------------
 */

void
TclpThreadDataKeyInit(keyPtr)
    Tcl_ThreadDataKey *keyPtr;	/* Identifier for the data chunk,
				 * really (pthread_key_t **) */
{
    DWORD *indexPtr;

    MASTER_LOCK;
    if (*keyPtr == NULL) {
	indexPtr = (DWORD *)ckalloc(sizeof(DWORD));
	*indexPtr = TlsAlloc();
................................................................................
 *	and initialize this the first time this Tcl_Condition is used.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ConditionWait(condPtr, mutexPtr, timePtr)
    Tcl_Condition *condPtr;	/* Really (pthread_cond_t **) */
    Tcl_Mutex *mutexPtr;	/* Really (pthread_mutex_t **) */
    Tcl_Time *timePtr;		/* Timeout on waiting period */
{
    HANDLE *eventPtr;
    CRITICAL_SECTION *csPtr;
    DWORD wtime;
















































    if (*condPtr == NULL) {
	MASTER_LOCK;

	/* 
	 * Double check inside mutex to avoid race,
	 * then initialize condition variable if necessary.

	 */

	if (*condPtr == NULL) {
	    eventPtr = (HANDLE *)ckalloc(sizeof(HANDLE));
	    *eventPtr = CreateEvent(NULL, TRUE /* manual reset */,
			FALSE /* non signaled */, NULL);

	    *condPtr = (Tcl_Condition)eventPtr;
	    TclRememberCondition(condPtr);
	}
	MASTER_UNLOCK;
    }
    csPtr = *((CRITICAL_SECTION **)mutexPtr);
    eventPtr = *((HANDLE **)condPtr);
    if (timePtr == NULL) {
	wtime = INFINITE;
    } else {
	wtime = timePtr->sec * 1000 + timePtr->usec / 1000;
    }

    /*
     * Clear the event it case there are old notifies.

     */

    ResetEvent(*eventPtr);


    LeaveCriticalSection(csPtr);









    /*
     * This point is a race with a notification, but this is handled
     * by the "stickiness" of the event.  If a notification occurs here,
     * then WaitForSingleObject will not block.







     */






    WaitForSingleObject(*eventPtr, wtime);





    /*
     * This point is a race with other waiters.  Someone else can grab
     * the mutex first.  This is why our caller must check its invariant
     * and perhaps wait again.


     */

    EnterCriticalSection(csPtr);





    /*
     * "Consume" the event - hmm - this may not be necessary because it
     * will be done before the next wait.




     */

    ResetEvent(*eventPtr);
















}

 
/*
 *----------------------------------------------------------------------
 *
 * Tcl_ConditionNotify --
................................................................................
 *----------------------------------------------------------------------
 */

void
Tcl_ConditionNotify(condPtr)
    Tcl_Condition *condPtr;
{
    HANDLE *eventPtr;

    if (condPtr != NULL) {
	eventPtr = *((HANDLE **)condPtr);


	/*
	 * The PulseEvent may not be necessary, but it's documentation says
	 * it releases all waiting processes, which is what we want.  However,
	 * it also clears the signal, which is not good because of the race
	 * in ConditionWait.  The SetEvent makes sure the signal remains
	 * even if there are no waiters, but we are not sure that it really
	 * marks all waiters as runnable.  So we do both.
	 */



	PulseEvent(*eventPtr);







	SetEvent(*eventPtr);


    } else {
	/*
	 * Noone has used the condition variable, so there are no waiters.
	 */
    }
}




























 
/*
 *----------------------------------------------------------------------
 *
 * TclpFinalizeCondition --
 *
 *	This procedure is invoked to clean up a condition variable.
................................................................................
 *----------------------------------------------------------------------
 */

void
TclpFinalizeCondition(condPtr)
    Tcl_Condition *condPtr;
{
    HANDLE *eventPtr = *(HANDLE **)condPtr;








    if (eventPtr != NULL) {
	CloseHandle(*eventPtr);
	ckfree((char *)eventPtr);
	*condPtr = NULL;
    }
}
#endif /* TCL_THREADS */







>







 







|
>
>
>
>
>
>
>
>
>


<
<
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







 







|







 







|
|


|
|
|
>
>
>

>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>



|
<
<
>



|
|
|
>
|





|







|
>


<
>
>
|
>
>
>
>
|
>
>
>
>

<
<
<
>
>
>
>
>
>
>

|
>
>
>
>
>
|
>
|
>
>
>

<
<
<
>
>

|
<
<
>
>
>
>
|
<
<
>
>
>
>
|

<
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







 







|
>

<
>


<
|
|
|
<
<


>
>
|
>
>
>
>
>
>
>
|
>
>







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







 







|
>
>
>
>
>
>
>
>
|
<
|




<
<
1
2
3
4
5
6
7
8
9
10
11
12
13
14
..
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51


52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
...
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
...
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685


686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711

712
713
714
715
716
717
718
719
720
721
722
723
724



725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745



746
747
748
749


750
751
752
753
754


755
756
757
758
759
760

761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
...
796
797
798
799
800
801
802
803
804
805

806
807
808

809
810
811


812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
...
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894

895
896
897
898
899


/* 
 * tclWinThread.c --
 *
 *	This file implements the Windows-specific thread operations.
 *
 * Copyright (c) 1998 by Sun Microsystems, Inc.
 * Copyright (c) 1999 by Scriptics Corporation
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * SCCS:  @(#) tclWinThrd.c 1.13 98/02/18 14:00:23
 */

................................................................................
 * This is the master lock used to serialize initialization and finalization
 * of Tcl as a whole.
 */

static CRITICAL_SECTION initLock;

/*
 * Condition variables are implemented with a combination of a 
 * per-thread Windows Event and a per-condition waiting queue.
 * The idea is that each thread has its own Event that it waits
 * on when it is doing a ConditionWait; it uses the same event for
 * all condition variables because it only waits on one at a time.
 * Each condition variable has a queue of waiting threads, and a 
 * mutex used to serialize access to this queue.
 *
 * Special thanks to David Nichols and
 * Jim Davidson for advice on the Condition Variable implementation.
 */



/*
 * The per-thread event and queue pointers.
 */

typedef struct ThreadSpecificData {
    HANDLE condEvent;			/* Per-thread condition event */
    struct ThreadSpecificData *nextPtr;	/* Queue pointers */
    struct ThreadSpecificData *prevPtr;
    int flags;				/* See flags below */
} ThreadSpecificData;
static Tcl_ThreadDataKey dataKey;

/*
 * State bits for the thread.
 * WIN_THREAD_UNINIT		Uninitialized.  Must be zero because
 *				of the way ThreadSpecificData is created.
 * WIN_THREAD_RUNNING		Running, not waiting.
 * WIN_THREAD_BLOCKED		Waiting, or trying to wait.
 * WIN_THREAD_DEAD		Dying - no per-thread event anymore.
 */ 

#define WIN_THREAD_UNINIT	0x0
#define WIN_THREAD_RUNNING	0x1
#define WIN_THREAD_BLOCKED	0x2
#define WIN_THREAD_DEAD		0x4

/*
 * The per condition queue pointers and the
 * Mutex used to serialize access to the queue.
 */

typedef struct WinCondition {
    CRITICAL_SECTION condLock;	/* Lock to serialize queuing on the condition */
    struct ThreadSpecificData *firstPtr;	/* Queue pointers */
    struct ThreadSpecificData *lastPtr;
} WinCondition;

static void *FinalizeConditionEvent(ClientData data);

 
/*
 *----------------------------------------------------------------------
 *
 * TclpThreadCreate --
 *
................................................................................
 *
 *----------------------------------------------------------------------
 */

void
TclpThreadDataKeyInit(keyPtr)
    Tcl_ThreadDataKey *keyPtr;	/* Identifier for the data chunk,
				 * really (DWORD **) */
{
    DWORD *indexPtr;

    MASTER_LOCK;
    if (*keyPtr == NULL) {
	indexPtr = (DWORD *)ckalloc(sizeof(DWORD));
	*indexPtr = TlsAlloc();
................................................................................
 *	and initialize this the first time this Tcl_Condition is used.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ConditionWait(condPtr, mutexPtr, timePtr)
    Tcl_Condition *condPtr;	/* Really (WinCondition **) */
    Tcl_Mutex *mutexPtr;	/* Really (CRITICAL_SECTION **) */
    Tcl_Time *timePtr;		/* Timeout on waiting period */
{
    WinCondition *winCondPtr;	/* Per-condition queue head */
    CRITICAL_SECTION *csPtr;	/* Caller's Mutex, after casting */
    DWORD wtime;		/* Windows time value */
    int timeout;		/* True if we got a timeout */
    int doExit = 0;		/* True if we need to do exit setup */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tsdPtr->flags & WIN_THREAD_DEAD) {
	/*
	 * No more per-thread event on which to wait.
	 */

	return;
    }

    /*
     * Self initialize the two parts of the contition.
     * The per-condition and per-thread parts need to be
     * handled independently.
     */

    if (tsdPtr->flags == WIN_THREAD_UNINIT) {
	MASTER_LOCK;

	/* 
	 * Create the per-thread event and queue pointers.
	 */

	if (tsdPtr->flags == WIN_THREAD_UNINIT) {
	    tsdPtr->condEvent = CreateEvent(NULL, TRUE /* manual reset */,
			FALSE /* non signaled */, NULL);
	    tsdPtr->nextPtr = NULL;
	    tsdPtr->prevPtr = NULL;
	    tsdPtr->flags = WIN_THREAD_RUNNING;
	    doExit = 1;
	}
	MASTER_UNLOCK;

	if (doExit) {
	    /*
	     * Create a per-thread exit handler to clean up the condEvent.
	     * We must be careful do do this outside the Master Lock
	     * because Tcl_CreateThreadExitHandler uses its own
	     * ThreadSpecificData, and initializing that may drop
	     * back into the Master Lock.
	     */
	    
	    Tcl_CreateThreadExitHandler(FinalizeConditionEvent, tsdPtr);
	}
    }

    if (*condPtr == NULL) {
	MASTER_LOCK;

	/*


	 * Initialize the per-condition queue pointers and Mutex.
	 */

	if (*condPtr == NULL) {
	    winCondPtr = (WinCondition *)ckalloc(sizeof(WinCondition));
	    InitializeCriticalSection(&winCondPtr->condLock);
	    winCondPtr->firstPtr = NULL;
	    winCondPtr->lastPtr = NULL;
	    *condPtr = (Tcl_Condition)winCondPtr;
	    TclRememberCondition(condPtr);
	}
	MASTER_UNLOCK;
    }
    csPtr = *((CRITICAL_SECTION **)mutexPtr);
    winCondPtr = *((WinCondition **)condPtr);
    if (timePtr == NULL) {
	wtime = INFINITE;
    } else {
	wtime = timePtr->sec * 1000 + timePtr->usec / 1000;
    }

    /*
     * Queue the thread on the condition, using
     * the per-condition lock for serialization.
     */


    tsdPtr->flags = WIN_THREAD_BLOCKED;
    tsdPtr->nextPtr = NULL;
    EnterCriticalSection(&winCondPtr->condLock);
    tsdPtr->prevPtr = winCondPtr->lastPtr;		/* A: */
    winCondPtr->lastPtr = tsdPtr;
    if (tsdPtr->prevPtr != NULL) {
        tsdPtr->prevPtr->nextPtr = tsdPtr;
    }
    if (winCondPtr->firstPtr == NULL) {
        winCondPtr->firstPtr = tsdPtr;
    }

    /*



     * Unlock the caller's mutex and wait for the condition, or a timeout.
     * There is a minor issue here in that we don't count down the
     * timeout if we get notified, but another thread grabs the condition
     * before we do.  In that race condition we'll wait again for the
     * full timeout.  Timed waits are dubious anyway.  Either you have
     * the locking protocol wrong and are masking a deadlock,
     * or you are using conditions to pause your thread.
     */
    
    LeaveCriticalSection(csPtr);
    timeout = 0;
    while (!timeout && (tsdPtr->flags & WIN_THREAD_BLOCKED)) {
	ResetEvent(tsdPtr->condEvent);
	LeaveCriticalSection(&winCondPtr->condLock);
	if (WaitForSingleObject(tsdPtr->condEvent, wtime) == WAIT_TIMEOUT) {
	    timeout = 1;
	}
	EnterCriticalSection(&winCondPtr->condLock);
    }

    /*



     * Be careful on timeouts because the signal might arrive right around
     * time time limit and someone else could have taken us off the queue.
     */
    


    if (timeout) {
	if (tsdPtr->flags & WIN_THREAD_RUNNING) {
	    timeout = 0;
	} else {
	    /*


	     * When dequeuing, we can leave the tsdPtr->nextPtr
	     * and tsdPtr->prevPtr with dangling pointers because
	     * they are reinitialilzed w/out reading them when the
	     * thread is enqueued later.
	     */


            if (winCondPtr->firstPtr == tsdPtr) {
                winCondPtr->firstPtr = tsdPtr->nextPtr;
            } else {
                tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr;
            }
            if (winCondPtr->lastPtr == tsdPtr) {
                winCondPtr->lastPtr = tsdPtr->prevPtr;
            } else {
                tsdPtr->nextPtr->prevPtr = tsdPtr->prevPtr;
            }
            tsdPtr->flags = WIN_THREAD_RUNNING;
	}
    }

    LeaveCriticalSection(&winCondPtr->condLock);
    EnterCriticalSection(csPtr);
}

 
/*
 *----------------------------------------------------------------------
 *
 * Tcl_ConditionNotify --
................................................................................
 *----------------------------------------------------------------------
 */

void
Tcl_ConditionNotify(condPtr)
    Tcl_Condition *condPtr;
{
    WinCondition *winCondPtr;
    ThreadSpecificData *tsdPtr;
    if (condPtr != NULL) {

	winCondPtr = *((WinCondition **)condPtr);

	/*

	 * Loop through all the threads waiting on the condition
	 * and notify them (i.e., broadcast semantics).  The queue
	 * manipulation is guarded by the per-condition coordinating mutex.


	 */

	EnterCriticalSection(&winCondPtr->condLock);
	while (winCondPtr->firstPtr != NULL) {
	    tsdPtr = winCondPtr->firstPtr;
	    winCondPtr->firstPtr = tsdPtr->nextPtr;
	    if (winCondPtr->lastPtr == tsdPtr) {
		winCondPtr->lastPtr = NULL;
	    }
	    tsdPtr->flags = WIN_THREAD_RUNNING;
	    tsdPtr->nextPtr = NULL;
	    tsdPtr->prevPtr = NULL;	/* Not strictly necessary, see A: */
	    SetEvent(tsdPtr->condEvent);
	}
	LeaveCriticalSection(&winCondPtr->condLock);
    } else {
	/*
	 * Noone has used the condition variable, so there are no waiters.
	 */
    }
}

 
/*
 *----------------------------------------------------------------------
 *
 * FinalizeConditionEvent --
 *
 *	This procedure is invoked to clean up the per-thread
 *	event used to implement condition waiting.
 *	This is only safe to call at the end of time.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The per-thread event is closed.
 *
 *----------------------------------------------------------------------
 */

static void *
FinalizeConditionEvent(data)
    ClientData data;
{
    ThreadSpecificData *tsdPtr = (ThreadSpecificData *)data;
    tsdPtr->flags = WIN_THREAD_DEAD;
    CloseHandle(tsdPtr->condEvent);
}
 
/*
 *----------------------------------------------------------------------
 *
 * TclpFinalizeCondition --
 *
 *	This procedure is invoked to clean up a condition variable.
................................................................................
 *----------------------------------------------------------------------
 */

void
TclpFinalizeCondition(condPtr)
    Tcl_Condition *condPtr;
{
    WinCondition *winCondPtr = *(WinCondition **)condPtr;

    /*
     * Note - this is called long after the thread-local storage is
     * reclaimed.  The per-thread condition waiting event is
     * reclaimed earlier in a per-thread exit handler, which is
     * called before thread local storage is reclaimed.
     */

    if (winCondPtr != NULL) {

	ckfree((char *)winCondPtr);
	*condPtr = NULL;
    }
}
#endif /* TCL_THREADS */