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
30 #include <sys/types.h>
32 #include <sys/queue.h>
36 #include "thr_private.h"
38 /* Spare thread stack. */
40 LIST_ENTRY(stack) qe; /* Stack queue linkage. */
41 size_t stacksize; /* Stack size (rounded up). */
42 size_t guardsize; /* Guard size. */
43 void *stackaddr; /* Stack address. */
47 * Default sized (stack and guard) spare stack queue. Stacks are cached
48 * to avoid additional complexity managing mmap()ed stack regions. Spare
49 * stacks are used in LIFO order to increase cache locality.
51 static LIST_HEAD(, stack) dstackq = LIST_HEAD_INITIALIZER(dstackq);
54 * Miscellaneous sized (non-default stack and/or guard) spare stack queue.
55 * Stacks are cached to avoid additional complexity managing mmap()ed
56 * stack regions. This list is unordered, since ordering on both stack
57 * size and guard size would be more trouble than it's worth. Stacks are
58 * allocated from this cache on a first size match basis.
60 static LIST_HEAD(, stack) mstackq = LIST_HEAD_INITIALIZER(mstackq);
63 * Base address of the last stack allocated (including its red zone, if
64 * there is one). Stacks are allocated contiguously, starting beyond the
65 * top of the main stack. When a new stack is created, a red zone is
66 * typically created (actually, the red zone is mapped with PROT_NONE) above
67 * the top of the stack, such that the stack will not be able to grow all
68 * the way to the bottom of the next stack. This isn't fool-proof. It is
69 * possible for a stack to grow by a large amount, such that it grows into
70 * the next stack, and as long as the memory within the red zone is never
71 * accessed, nothing will prevent one thread stack from trouncing all over
75 * . . . . . . . . . . . . . . . . . .
77 * | stack 3 | start of 3rd thread stack
78 * +-----------------------------------+
80 * | Red Zone (guard page) | red zone for 2nd thread
82 * +-----------------------------------+
83 * | stack 2 - _thr_stack_default | top of 2nd thread stack
89 * +-----------------------------------+ <-- start of 2nd thread stack
91 * | Red Zone | red zone for 1st thread
93 * +-----------------------------------+
94 * | stack 1 - _thr_stack_default | top of 1st thread stack
100 * +-----------------------------------+ <-- start of 1st thread stack
101 * | | (initial value of last_stack)
103 * | | red zone for main thread
104 * +-----------------------------------+
105 * | USRSTACK - _thr_stack_initial | top of main thread stack
111 * +-----------------------------------+ <-- start of main thread stack
116 static char *last_stack = NULL;
119 * Round size up to the nearest multiple of
123 round_up(size_t size)
125 if (size % _thr_page_size != 0)
126 size = ((size / _thr_page_size) + 1) *
132 _thr_stack_alloc(struct pthread_attr *attr)
134 struct pthread *curthread = _get_curthread();
135 struct stack *spare_stack;
141 * Round up stack size to nearest multiple of _thr_page_size so
142 * that mmap() * will work. If the stack size is not an even
143 * multiple, we end up initializing things such that there is
144 * unused space above the beginning of the stack, so the stack
145 * sits snugly against its guard.
147 stacksize = round_up(attr->stacksize_attr);
148 guardsize = round_up(attr->guardsize_attr);
150 attr->stackaddr_attr = NULL;
151 attr->flags &= ~THR_STACK_USER;
154 * Use the garbage collector lock for synchronization of the
155 * spare stack lists and allocations from usrstack.
157 THREAD_LIST_LOCK(curthread);
159 * If the stack and guard sizes are default, try to allocate a stack
160 * from the default-size stack cache:
162 if ((stacksize == THR_STACK_DEFAULT) &&
163 (guardsize == _thr_guard_default)) {
164 if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) {
165 /* Use the spare stack. */
166 LIST_REMOVE(spare_stack, qe);
167 attr->stackaddr_attr = spare_stack->stackaddr;
171 * The user specified a non-default stack and/or guard size, so try to
172 * allocate a stack from the non-default size stack cache, using the
173 * rounded up stack size (stack_size) in the search:
176 LIST_FOREACH(spare_stack, &mstackq, qe) {
177 if (spare_stack->stacksize == stacksize &&
178 spare_stack->guardsize == guardsize) {
179 LIST_REMOVE(spare_stack, qe);
180 attr->stackaddr_attr = spare_stack->stackaddr;
185 if (attr->stackaddr_attr != NULL) {
186 /* A cached stack was found. Release the lock. */
187 THREAD_LIST_UNLOCK(curthread);
190 /* Allocate a stack from usrstack. */
191 if (last_stack == NULL)
192 last_stack = _usrstack - _thr_stack_initial -
195 /* Allocate a new stack. */
196 stackaddr = last_stack - stacksize - guardsize;
199 * Even if stack allocation fails, we don't want to try to
200 * use this location again, so unconditionally decrement
201 * last_stack. Under normal operating conditions, the most
202 * likely reason for an mmap() error is a stack overflow of
203 * the adjacent thread stack.
205 last_stack -= (stacksize + guardsize);
207 /* Release the lock before mmap'ing it. */
208 THREAD_LIST_UNLOCK(curthread);
210 /* Map the stack and guard page together, and split guard
211 page from allocated space: */
212 if ((stackaddr = mmap(stackaddr, stacksize+guardsize,
213 PROT_READ | PROT_WRITE, MAP_STACK,
214 -1, 0)) != MAP_FAILED &&
216 mprotect(stackaddr, guardsize, PROT_NONE) == 0)) {
217 stackaddr += guardsize;
219 if (stackaddr != MAP_FAILED)
220 munmap(stackaddr, stacksize + guardsize);
223 attr->stackaddr_attr = stackaddr;
225 if (attr->stackaddr_attr != NULL)
231 /* This function must be called with _thread_list_lock held. */
233 _thr_stack_free(struct pthread_attr *attr)
235 struct stack *spare_stack;
237 if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0)
238 && (attr->stackaddr_attr != NULL)) {
239 spare_stack = (struct stack *)
240 ((char *)attr->stackaddr_attr +
241 attr->stacksize_attr - sizeof(struct stack));
242 spare_stack->stacksize = round_up(attr->stacksize_attr);
243 spare_stack->guardsize = round_up(attr->guardsize_attr);
244 spare_stack->stackaddr = attr->stackaddr_attr;
246 if (spare_stack->stacksize == THR_STACK_DEFAULT &&
247 spare_stack->guardsize == _thr_guard_default) {
248 /* Default stack/guard size. */
249 LIST_INSERT_HEAD(&dstackq, spare_stack, qe);
251 /* Non-default stack/guard size. */
252 LIST_INSERT_HEAD(&mstackq, spare_stack, qe);
254 attr->stackaddr_attr = NULL;