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