/*
* Copyright (c) 2001 Daniel Eischen <deischen@freebsd.org>
* Copyright (c) 2000-2001 Jason Evans <jasone@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/user.h>
#include <stdlib.h>
#include <pthread.h>
#include "thr_private.h"
/* Spare thread stack. */
struct stack {
LIST_ENTRY(stack) qe; /* Stack queue linkage. */
size_t stacksize; /* Stack size (rounded up). */
size_t guardsize; /* Guard size. */
void *stackaddr; /* Stack address. */
};
/*
* Default sized (stack and guard) spare stack queue. Stacks are cached to
* avoid additional complexity managing mmap()ed stack regions. Spare stacks
* are used in LIFO order to increase cache locality.
*/
static LIST_HEAD(, stack) _dstackq = LIST_HEAD_INITIALIZER(_dstackq);
/*
* Miscellaneous sized (non-default stack and/or guard) spare stack queue.
* Stacks are cached to avoid additional complexity managing mmap()ed stack
* regions. This list is unordered, since ordering on both stack size and guard
* size would be more trouble than it's worth. Stacks are allocated from this
* cache on a first size match basis.
*/
static LIST_HEAD(, stack) _mstackq = LIST_HEAD_INITIALIZER(_mstackq);
/**
* Base address of the last stack allocated (including its red zone, if there is
* one). Stacks are allocated contiguously, starting beyond the top of the main
* stack. When a new stack is created, a red zone is typically created
* (actually, the red zone is simply left unmapped) above the top of the stack,
* such that the stack will not be able to grow all the way to the bottom of the
* next stack. This isn't fool-proof. It is possible for a stack to grow by a
* large amount, such that it grows into the next stack, and as long as the
* memory within the red zone is never accessed, nothing will prevent one thread
* stack from trouncing all over the next.
*
* low memory
* . . . . . . . . . . . . . . . . . .
* | |
* | stack 3 | start of 3rd thread stack
* +-----------------------------------+
* | |
* | Red Zone (guard page) | red zone for 2nd thread
* | |
* +-----------------------------------+
* | stack 2 - PTHREAD_STACK_DEFAULT | top of 2nd thread stack
* | |
* | |
* | |
* | |
* | stack 2 |
* +-----------------------------------+ <-- start of 2nd thread stack
* | |
* | Red Zone | red zone for 1st thread
* | |
* +-----------------------------------+
* | stack 1 - PTHREAD_STACK_DEFAULT | top of 1st thread stack
* | |
* | |
* | |
* | |
* | stack 1 |
* +-----------------------------------+ <-- start of 1st thread stack
* | | (initial value of last_stack)
* | Red Zone |
* | | red zone for main thread
* +-----------------------------------+
* | USRSTACK - PTHREAD_STACK_INITIAL | top of main thread stack
* | | ^
* | | |
* | | |
* | | | stack growth
* | |
* +-----------------------------------+ <-- start of main thread stack
* (USRSTACK)
* high memory
*
*/
static void * last_stack;
void *
_thread_stack_alloc(size_t stacksize, size_t guardsize)
{
void *stack = NULL;
struct stack *spare_stack;
size_t stack_size;
/*
* Round up stack size to nearest multiple of _pthread_page_size,
* so that mmap() * will work. If the stack size is not an even
* multiple, we end up initializing things such that there is unused
* space above the beginning of the stack, so the stack sits snugly
* against its guard.
*/
if (stacksize % _pthread_page_size != 0)
stack_size = ((stacksize / _pthread_page_size) + 1) *
_pthread_page_size;
else
stack_size = stacksize;
/*
* If the stack and guard sizes are default, try to allocate a stack
* from the default-size stack cache:
*/
if (stack_size == PTHREAD_STACK_DEFAULT &&
guardsize == _pthread_guard_default) {
/*
* Use the garbage collector mutex for synchronization of the
* spare stack list.
*/
STACK_LOCK;
if ((spare_stack = LIST_FIRST(&_dstackq)) != NULL) {
/* Use the spare stack. */
LIST_REMOVE(spare_stack, qe);
stack = spare_stack->stackaddr;
}
/* Unlock the garbage collector mutex. */
STACK_UNLOCK;
}
/*
* The user specified a non-default stack and/or guard size, so try to
* allocate a stack from the non-default size stack cache, using the
* rounded up stack size (stack_size) in the search:
*/
else {
/*
* Use the garbage collector mutex for synchronization of the
* spare stack list.
*/
STACK_LOCK;
LIST_FOREACH(spare_stack, &_mstackq, qe) {
if (spare_stack->stacksize == stack_size &&
spare_stack->guardsize == guardsize) {
LIST_REMOVE(spare_stack, qe);
stack = spare_stack->stackaddr;
break;
}
}
/* Unlock the garbage collector mutex. */
STACK_UNLOCK;
}
/* Check if a stack was not allocated from a stack cache: */
if (stack == NULL) {
if (last_stack == NULL)
last_stack = _usrstack - PTHREAD_STACK_INITIAL -
_pthread_guard_default;
/* Allocate a new stack. */
stack = last_stack - stack_size;
/*
* Even if stack allocation fails, we don't want to try to use
* this location again, so unconditionally decrement
* last_stack. Under normal operating conditions, the most
* likely reason for an mmap() error is a stack overflow of the
* adjacent thread stack.
*/
last_stack -= (stack_size + guardsize);
/* Stack: */
if (mmap(stack, stack_size, PROT_READ | PROT_WRITE, MAP_STACK,
-1, 0) == MAP_FAILED)
stack = NULL;
}
return (stack);
}
/* This function must be called with the 'dead thread list' lock held. */
void
_thread_stack_free(void *stack, size_t stacksize, size_t guardsize)
{
struct stack *spare_stack;
spare_stack = (stack + stacksize - sizeof(struct stack));
/* Round stacksize up to nearest multiple of _pthread_page_size. */
if (stacksize % _pthread_page_size != 0) {
spare_stack->stacksize =
((stacksize / _pthread_page_size) + 1) *
_pthread_page_size;
} else
spare_stack->stacksize = stacksize;
spare_stack->guardsize = guardsize;
spare_stack->stackaddr = stack;
if (spare_stack->stacksize == PTHREAD_STACK_DEFAULT &&
spare_stack->guardsize == _pthread_guard_default) {
/* Default stack/guard size. */
LIST_INSERT_HEAD(&_dstackq, spare_stack, qe);
} else {
/* Non-default stack/guard size. */
LIST_INSERT_HEAD(&_mstackq, spare_stack, qe);
}
}
