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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "primpl.h"
/* 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(); }
void _PR_CleanupStacks(void) {
if (_pr_stackLock) {
PR_DestroyLock(_pr_stackLock);
_pr_stackLock = NULL;
}
}
/*
** 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 = (char*)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);
}