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
29 #include <sys/types.h>
31 #include <sys/queue.h>
34 #include "thr_private.h"
36 /* Spare thread stack. */
38 LIST_ENTRY(stack) qe; /* Stack queue linkage. */
39 size_t stacksize; /* Stack size (rounded up). */
40 size_t guardsize; /* Guard size. */
41 void *stackaddr; /* Stack address. */
45 * Default sized (stack and guard) spare stack queue. Stacks are cached
46 * to avoid additional complexity managing mmap()ed stack regions. Spare
47 * stacks are used in LIFO order to increase cache locality.
49 static LIST_HEAD(, stack) dstackq = LIST_HEAD_INITIALIZER(dstackq);
52 * Miscellaneous sized (non-default stack and/or guard) spare stack queue.
53 * Stacks are cached to avoid additional complexity managing mmap()ed
54 * stack regions. This list is unordered, since ordering on both stack
55 * size and guard size would be more trouble than it's worth. Stacks are
56 * allocated from this cache on a first size match basis.
58 static LIST_HEAD(, stack) mstackq = LIST_HEAD_INITIALIZER(mstackq);
61 * Base address of the last stack allocated (including its red zone, if
62 * there is one). Stacks are allocated contiguously, starting beyond the
63 * top of the main stack. When a new stack is created, a red zone is
64 * typically created (actually, the red zone is mapped with PROT_NONE) above
65 * the top of the stack, such that the stack will not be able to grow all
66 * the way to the bottom of the next stack. This isn't fool-proof. It is
67 * possible for a stack to grow by a large amount, such that it grows into
68 * the next stack, and as long as the memory within the red zone is never
69 * accessed, nothing will prevent one thread stack from trouncing all over
73 * . . . . . . . . . . . . . . . . . .
75 * | stack 3 | start of 3rd thread stack
76 * +-----------------------------------+
78 * | Red Zone (guard page) | red zone for 2nd thread
80 * +-----------------------------------+
81 * | stack 2 - PTHREAD_STACK_DEFAULT | top of 2nd thread stack
87 * +-----------------------------------+ <-- start of 2nd thread stack
89 * | Red Zone | red zone for 1st thread
91 * +-----------------------------------+
92 * | stack 1 - PTHREAD_STACK_DEFAULT | top of 1st thread stack
98 * +-----------------------------------+ <-- start of 1st thread stack
99 * | | (initial value of last_stack)
101 * | | red zone for main thread
102 * +-----------------------------------+
103 * | USRSTACK - PTHREAD_STACK_INITIAL | top of main thread stack
109 * +-----------------------------------+ <-- start of main thread stack
114 static void *last_stack = NULL;
117 * Round size up to the nearest multiple of
121 round_up(size_t size)
123 if (size % _thr_page_size != 0)
124 size = ((size / _thr_page_size) + 1) *
130 _thr_stack_alloc(struct pthread_attr *attr)
132 struct stack *spare_stack;
140 * Round up stack size to nearest multiple of _thr_page_size so
141 * that mmap() * will work. If the stack size is not an even
142 * multiple, we end up initializing things such that there is
143 * unused space above the beginning of the stack, so the stack
144 * sits snugly against its guard.
146 stacksize = round_up(attr->stacksize_attr);
147 guardsize = round_up(attr->guardsize_attr);
149 attr->stackaddr_attr = NULL;
150 attr->flags &= ~THR_STACK_USER;
153 * Use the garbage collector lock for synchronization of the
154 * spare stack lists and allocations from usrstack.
156 crit = _kse_critical_enter();
157 curkse = _get_curkse();
158 KSE_LOCK_ACQUIRE(curkse, &_thread_list_lock);
160 * If the stack and guard sizes are default, try to allocate a stack
161 * from the default-size stack cache:
163 if ((stacksize == _thr_stack_default) &&
164 (guardsize == _thr_guard_default)) {
165 if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) {
166 /* Use the spare stack. */
167 LIST_REMOVE(spare_stack, qe);
168 attr->stackaddr_attr = spare_stack->stackaddr;
172 * The user specified a non-default stack and/or guard size, so try to
173 * allocate a stack from the non-default size stack cache, using the
174 * rounded up stack size (stack_size) in the search:
177 LIST_FOREACH(spare_stack, &mstackq, qe) {
178 if (spare_stack->stacksize == stacksize &&
179 spare_stack->guardsize == guardsize) {
180 LIST_REMOVE(spare_stack, qe);
181 attr->stackaddr_attr = spare_stack->stackaddr;
186 if (attr->stackaddr_attr != NULL) {
187 /* A cached stack was found. Release the lock. */
188 KSE_LOCK_RELEASE(curkse, &_thread_list_lock);
189 _kse_critical_leave(crit);
192 /* Allocate a stack from usrstack. */
193 if (last_stack == NULL)
194 last_stack = _usrstack - _thr_stack_initial -
197 /* Allocate a new stack. */
198 stackaddr = last_stack - stacksize - guardsize;
201 * Even if stack allocation fails, we don't want to try to
202 * use this location again, so unconditionally decrement
203 * last_stack. Under normal operating conditions, the most
204 * likely reason for an mmap() error is a stack overflow of
205 * the adjacent thread stack.
207 last_stack -= (stacksize + guardsize);
209 /* Release the lock before mmap'ing it. */
210 KSE_LOCK_RELEASE(curkse, &_thread_list_lock);
211 _kse_critical_leave(crit);
213 /* Map the stack and guard page together, and split guard
214 page from allocated space: */
215 if ((stackaddr = mmap(stackaddr, stacksize+guardsize,
216 PROT_READ | PROT_WRITE, MAP_STACK,
217 -1, 0)) != MAP_FAILED &&
219 mprotect(stackaddr, guardsize, PROT_NONE) == 0)) {
220 stackaddr += guardsize;
222 if (stackaddr != MAP_FAILED)
223 munmap(stackaddr, stacksize + guardsize);
226 attr->stackaddr_attr = stackaddr;
228 if (attr->stackaddr_attr != NULL)
234 /* This function must be called with _thread_list_lock held. */
236 _thr_stack_free(struct pthread_attr *attr)
238 struct stack *spare_stack;
240 if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0)
241 && (attr->stackaddr_attr != NULL)) {
242 spare_stack = (attr->stackaddr_attr + attr->stacksize_attr
243 - sizeof(struct stack));
244 spare_stack->stacksize = round_up(attr->stacksize_attr);
245 spare_stack->guardsize = round_up(attr->guardsize_attr);
246 spare_stack->stackaddr = attr->stackaddr_attr;
248 if (spare_stack->stacksize == _thr_stack_default &&
249 spare_stack->guardsize == _thr_guard_default) {
250 /* Default stack/guard size. */
251 LIST_INSERT_HEAD(&dstackq, spare_stack, qe);
253 /* Non-default stack/guard size. */
254 LIST_INSERT_HEAD(&mstackq, spare_stack, qe);
256 attr->stackaddr_attr = NULL;