Tools/WinSN5.0Ver.iso/NETSCAP.50/WIN1998.ZIP/ns/nsprpub/pr/src/threads/combined/prustack.c

C/C++ Source or Header | 1998-04-08 | 4.9 KB | 184 lines

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/*
 * The contents of this file are subject to the Netscape Public License
 * Version 1.0 (the "NPL"); you may not use this file except in
 * compliance with the NPL.  You may obtain a copy of the NPL at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the NPL is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
 * for the specific language governing rights and limitations under the
 * NPL.
 *
 * The Initial Developer of this code under the NPL is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
 * Reserved.
 */

#include "primpl.h"

#ifdef XP_UNIX
#include <sys/mman.h>
#endif

/* List of free stack virtual memory chunks */
PRLock *_pr_stackLock;
PRCList _pr_freeStacks = PR_INIT_STATIC_CLIST(&_pr_freeStacks);
PRIntn _pr_numFreeStacks;
PRIntn _pr_maxFreeStacks = 4;

#ifdef DEBUG
/*
** A variable that can be set via the debugger...
*/
PRBool _pr_debugStacks = PR_FALSE;
#endif

/* How much space to leave between the stacks, at each end */
#define REDZONE        (2 << _pr_pageShift)

#define _PR_THREAD_STACK_PTR(_qp) \
    ((PRThreadStack*) ((char*) (_qp) - offsetof(PRThreadStack,links)))

void _PR_InitStacks(void)
{
    _pr_stackLock = PR_NewLock();
}

/*
** Allocate a stack for a thread.
*/
PRThreadStack *_PR_NewStack(PRUint32 stackSize)
{
    PRCList *qp;
    PRThreadStack *ts;
    PRThread *thr;

    /*
    ** Trim the list of free stacks. Trim it backwards, tossing out the
    ** oldest stack found first (this way more recent stacks have a
    ** chance of being present in the data cache).
    */
    PR_Lock(_pr_stackLock);
    qp = _pr_freeStacks.prev;
    while ((_pr_numFreeStacks > _pr_maxFreeStacks) && (qp != &_pr_freeStacks)) {
    ts = _PR_THREAD_STACK_PTR(qp);
    thr = _PR_THREAD_STACK_TO_PTR(ts);
    qp = qp->prev;
    /*
     * skip stacks which are still being used
     */
    if (thr->no_sched)
        continue;
    PR_REMOVE_LINK(&ts->links);

    /* Give platform OS to clear out the stack for debugging */
    _PR_MD_CLEAR_STACK(ts);

    _pr_numFreeStacks--;
    PR_DestroySegment(ts->seg);
    PR_DELETE(ts);
    }

    /*
    ** Find a free thread stack. This searches the list of free'd up
    ** virtually mapped thread stacks.
    */
    qp = _pr_freeStacks.next;
    ts = 0;
    while (qp != &_pr_freeStacks) {
    ts = _PR_THREAD_STACK_PTR(qp);
    thr = _PR_THREAD_STACK_TO_PTR(ts);
    qp = qp->next;
    /*
     * skip stacks which are still being used
     */
    if ((!(thr->no_sched)) && ((ts->allocSize - 2*REDZONE) >= stackSize)) {
        /*
        ** Found a stack that is not in use and is big enough. Change
        ** stackSize to fit it.
        */
        stackSize = ts->allocSize - 2*REDZONE;
        PR_REMOVE_LINK(&ts->links);
        _pr_numFreeStacks--;
        ts->links.next = 0;
        ts->links.prev = 0;
        PR_Unlock(_pr_stackLock);
        goto done;
    }
    ts = 0;
    }
    PR_Unlock(_pr_stackLock);

    if (!ts) {
    /* Make a new thread stack object. */
    ts = PR_NEWZAP(PRThreadStack);
    if (!ts) {
        return NULL;
    }

    /*
    ** Assign some of the virtual space to the new stack object. We
    ** may not get that piece of VM, but if nothing else we will
    ** advance the pointer so we don't collide (unless the OS screws
    ** up).
    */
    ts->allocSize = stackSize + 2*REDZONE;
    ts->seg = PR_NewSegment(ts->allocSize, 0);
    if (!ts->seg) {
        PR_DELETE(ts);
        return NULL;
    }
    }

  done:
    ts->allocBase = ts->seg->vaddr;
    ts->flags = _PR_STACK_MAPPED;
    ts->stackSize = stackSize;

#ifdef HAVE_STACK_GROWING_UP
    ts->stackTop = ts->allocBase + REDZONE;
    ts->stackBottom = ts->stackTop + stackSize;
#else
    ts->stackBottom = ts->allocBase + REDZONE;
    ts->stackTop = ts->stackBottom + stackSize;
#endif

    PR_LOG(_pr_thread_lm, PR_LOG_NOTICE,
       ("thread stack: base=0x%x limit=0x%x bottom=0x%x top=0x%x\n",
        ts->allocBase, ts->allocBase + ts->allocSize - 1,
        ts->allocBase + REDZONE,
        ts->allocBase + REDZONE + stackSize - 1));

    _PR_MD_INIT_STACK(ts,REDZONE);

    return ts;
}

/*
** Free the stack for the current thread
*/
void _PR_FreeStack(PRThreadStack *ts)
{
    if (!ts) {
    return;
    }
    if (ts->flags & _PR_STACK_PRIMORDIAL) {
    PR_DELETE(ts);
    return;
    }

    /*
    ** Put the stack on the free list. This is done because we are still
    ** using the stack. Next time a thread is created we will trim the
    ** list down; it's safe to do it then because we will have had to
    ** context switch to a live stack before another thread can be
    ** created.
    */
    PR_Lock(_pr_stackLock);
    PR_APPEND_LINK(&ts->links, _pr_freeStacks.prev);
    _pr_numFreeStacks++;
    PR_Unlock(_pr_stackLock);
}