2 * Copyright (c) 2001 Daniel Eischen <deischen@freebsd.org>
3 * Copyright (c) 2000-2001 Jason Evans <jasone@freebsd.org>
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * $FreeBSD: src/lib/libpthread/thread/thr_stack.c,v 1.9 2004/10/06 08:11:07 davidxu Exp $
28 * $DragonFly: src/lib/libthread_xu/thread/thr_stack.c,v 1.4 2006/04/06 13:03:09 davidxu Exp $
30 #include <sys/types.h>
32 #include <sys/queue.h>
34 #include <machine/tls.h>
38 #include "thr_private.h"
40 /* Spare thread stack. */
42 LIST_ENTRY(stack) qe; /* Stack queue linkage. */
43 size_t stacksize; /* Stack size (rounded up). */
44 size_t guardsize; /* Guard size. */
45 void *stackaddr; /* Stack address. */
49 * Default sized (stack and guard) spare stack queue. Stacks are cached
50 * to avoid additional complexity managing mmap()ed stack regions. Spare
51 * stacks are used in LIFO order to increase cache locality.
53 static LIST_HEAD(, stack) dstackq = LIST_HEAD_INITIALIZER(dstackq);
56 * Miscellaneous sized (non-default stack and/or guard) spare stack queue.
57 * Stacks are cached to avoid additional complexity managing mmap()ed
58 * stack regions. This list is unordered, since ordering on both stack
59 * size and guard size would be more trouble than it's worth. Stacks are
60 * allocated from this cache on a first size match basis.
62 static LIST_HEAD(, stack) mstackq = LIST_HEAD_INITIALIZER(mstackq);
65 * Base address of the last stack allocated (including its red zone, if
66 * there is one). Stacks are allocated contiguously, starting beyond the
67 * top of the main stack. When a new stack is created, a red zone is
68 * typically created (actually, the red zone is mapped with PROT_NONE) above
69 * the top of the stack, such that the stack will not be able to grow all
70 * the way to the bottom of the next stack. This isn't fool-proof. It is
71 * possible for a stack to grow by a large amount, such that it grows into
72 * the next stack, and as long as the memory within the red zone is never
73 * accessed, nothing will prevent one thread stack from trouncing all over
77 * . . . . . . . . . . . . . . . . . .
79 * | stack 3 | start of 3rd thread stack
80 * +-----------------------------------+
82 * | Red Zone (guard page) | red zone for 2nd thread
84 * +-----------------------------------+
85 * | stack 2 - _thr_stack_default | top of 2nd thread stack
91 * +-----------------------------------+ <-- start of 2nd thread stack
93 * | Red Zone | red zone for 1st thread
95 * +-----------------------------------+
96 * | stack 1 - _thr_stack_default | top of 1st thread stack
102 * +-----------------------------------+ <-- start of 1st thread stack
103 * | | (initial value of last_stack)
105 * | | red zone for main thread
106 * +-----------------------------------+
107 * | USRSTACK - _thr_stack_initial | top of main thread stack
113 * +-----------------------------------+ <-- start of main thread stack
118 static char *last_stack = NULL;
121 * Round size up to the nearest multiple of
125 round_up(size_t size)
127 if (size % _thr_page_size != 0)
128 size = ((size / _thr_page_size) + 1) *
134 _thr_stack_alloc(struct pthread_attr *attr)
136 struct pthread *curthread = tls_get_curthread();
137 struct stack *spare_stack;
143 * Round up stack size to nearest multiple of _thr_page_size so
144 * that mmap() * will work. If the stack size is not an even
145 * multiple, we end up initializing things such that there is
146 * unused space above the beginning of the stack, so the stack
147 * sits snugly against its guard.
149 stacksize = round_up(attr->stacksize_attr);
150 guardsize = round_up(attr->guardsize_attr);
152 attr->stackaddr_attr = NULL;
153 attr->flags &= ~THR_STACK_USER;
156 * Use the garbage collector lock for synchronization of the
157 * spare stack lists and allocations from usrstack.
159 THREAD_LIST_LOCK(curthread);
161 * If the stack and guard sizes are default, try to allocate a stack
162 * from the default-size stack cache:
164 if ((stacksize == THR_STACK_DEFAULT) &&
165 (guardsize == _thr_guard_default)) {
166 if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) {
167 /* Use the spare stack. */
168 LIST_REMOVE(spare_stack, qe);
169 attr->stackaddr_attr = spare_stack->stackaddr;
173 * The user specified a non-default stack and/or guard size, so try to
174 * allocate a stack from the non-default size stack cache, using the
175 * rounded up stack size (stack_size) in the search:
178 LIST_FOREACH(spare_stack, &mstackq, qe) {
179 if (spare_stack->stacksize == stacksize &&
180 spare_stack->guardsize == guardsize) {
181 LIST_REMOVE(spare_stack, qe);
182 attr->stackaddr_attr = spare_stack->stackaddr;
187 if (attr->stackaddr_attr != NULL) {
188 /* A cached stack was found. Release the lock. */
189 THREAD_LIST_UNLOCK(curthread);
192 /* Allocate a stack from usrstack. */
193 if (last_stack == NULL) {
194 last_stack = _usrstack - _thr_stack_initial -
198 /* Allocate a new stack. */
199 stackaddr = last_stack - stacksize - guardsize;
202 * Even if stack allocation fails, we don't want to try to
203 * use this location again, so unconditionally decrement
204 * last_stack. Under normal operating conditions, the most
205 * likely reason for an mmap() error is a stack overflow of
206 * the adjacent thread stack.
208 last_stack -= (stacksize + guardsize);
210 /* Release the lock before mmap'ing it. */
211 THREAD_LIST_UNLOCK(curthread);
214 * Map the stack and guard page together then split the
215 * guard page from allocated space.
217 * NOTE: MAP_STACK mappings are grow-down and the
218 * initial mapping does not actually extend to the guard
219 * area, so creating the guard requires doing a fixed
220 * anonymous mmap of the guard area.
222 stackaddr = mmap(stackaddr, stacksize + guardsize,
223 PROT_READ | PROT_WRITE,
224 MAP_STACK | MAP_TRYFIXED, -1, 0);
225 if (stackaddr != MAP_FAILED && guardsize) {
226 if (mmap(stackaddr, guardsize, 0,
227 MAP_ANON | MAP_FIXED, -1, 0) == MAP_FAILED) {
228 munmap(stackaddr, stacksize + guardsize);
229 stackaddr = MAP_FAILED;
231 stackaddr += guardsize;
234 if (stackaddr == MAP_FAILED)
236 attr->stackaddr_attr = stackaddr;
238 if (attr->stackaddr_attr != NULL)
244 /* This function must be called with _thread_list_lock held. */
246 _thr_stack_free(struct pthread_attr *attr)
248 struct stack *spare_stack;
250 if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0)
251 && (attr->stackaddr_attr != NULL)) {
252 spare_stack = (struct stack *)((char *)attr->stackaddr_attr +
253 attr->stacksize_attr - sizeof(struct stack));
254 spare_stack->stacksize = round_up(attr->stacksize_attr);
255 spare_stack->guardsize = round_up(attr->guardsize_attr);
256 spare_stack->stackaddr = attr->stackaddr_attr;
258 if (spare_stack->stacksize == THR_STACK_DEFAULT &&
259 spare_stack->guardsize == _thr_guard_default) {
260 /* Default stack/guard size. */
261 LIST_INSERT_HEAD(&dstackq, spare_stack, qe);
263 /* Non-default stack/guard size. */
264 LIST_INSERT_HEAD(&mstackq, spare_stack, qe);
266 attr->stackaddr_attr = NULL;