ca1c469cc7
lock. It's not really necessary and we don't need the added complexity or potential for deadlocks. Approved by: re/blanket libthr
237 lines
8.5 KiB
C
237 lines
8.5 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/param.h>
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#include <sys/queue.h>
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#include <sys/user.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 to
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* avoid additional complexity managing mmap()ed stack regions. Spare stacks
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* 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 stack
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* regions. This list is unordered, since ordering on both stack size and guard
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* size would be more trouble than it's worth. Stacks are allocated from this
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* 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 there is
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* one). Stacks are allocated contiguously, starting beyond the top of the main
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* stack. When a new stack is created, a red zone is typically created
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* (actually, the red zone is simply left unmapped) above the top of the stack,
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* such that the stack will not be able to grow all the way to the bottom of the
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* next stack. This isn't fool-proof. It is possible for a stack to grow by a
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* large amount, such that it grows into the next stack, and as long as the
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* memory within the red zone is never accessed, nothing will prevent one thread
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* stack from trouncing all over 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 - PTHREAD_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 - PTHREAD_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 - PTHREAD_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 void * last_stack;
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void *
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_thread_stack_alloc(size_t stacksize, size_t guardsize)
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{
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void *stack = NULL;
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struct stack *spare_stack;
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size_t stack_size;
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/*
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* Round up stack size to nearest multiple of _pthread_page_size,
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* so 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 unused
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* space above the beginning of the stack, so the stack sits snugly
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* against its guard.
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*/
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if (stacksize % _pthread_page_size != 0)
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stack_size = ((stacksize / _pthread_page_size) + 1) *
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_pthread_page_size;
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else
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stack_size = stacksize;
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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 (stack_size == PTHREAD_STACK_DEFAULT &&
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guardsize == _pthread_guard_default) {
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/*
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* Use the garbage collector mutex for synchronization of the
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* spare stack list.
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*/
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STACK_LOCK;
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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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stack = spare_stack->stackaddr;
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}
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/* Unlock the garbage collector mutex. */
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STACK_UNLOCK;
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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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/*
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* Use the garbage collector mutex for synchronization of the
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* spare stack list.
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*/
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STACK_LOCK;
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LIST_FOREACH(spare_stack, &_mstackq, qe) {
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if (spare_stack->stacksize == stack_size &&
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spare_stack->guardsize == guardsize) {
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LIST_REMOVE(spare_stack, qe);
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stack = spare_stack->stackaddr;
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break;
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}
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}
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/* Unlock the garbage collector mutex. */
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STACK_UNLOCK;
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}
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/* Check if a stack was not allocated from a stack cache: */
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if (stack == NULL) {
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if (last_stack == NULL)
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last_stack = _usrstack - PTHREAD_STACK_INITIAL -
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_pthread_guard_default;
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/* Allocate a new stack. */
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stack = last_stack - stack_size;
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/*
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* Even if stack allocation fails, we don't want to try to use
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* 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 the
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* adjacent thread stack.
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*/
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last_stack -= (stack_size + guardsize);
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/* Stack: */
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if (mmap(stack, stack_size, PROT_READ | PROT_WRITE, MAP_STACK,
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-1, 0) == MAP_FAILED)
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stack = NULL;
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}
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return (stack);
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}
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/* This function must be called with the 'dead thread list' lock held. */
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void
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_thread_stack_free(void *stack, size_t stacksize, size_t guardsize)
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{
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struct stack *spare_stack;
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spare_stack = (stack + stacksize - sizeof(struct stack));
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/* Round stacksize up to nearest multiple of _pthread_page_size. */
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if (stacksize % _pthread_page_size != 0) {
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spare_stack->stacksize =
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((stacksize / _pthread_page_size) + 1) *
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_pthread_page_size;
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} else
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spare_stack->stacksize = stacksize;
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spare_stack->guardsize = guardsize;
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spare_stack->stackaddr = stack;
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if (spare_stack->stacksize == PTHREAD_STACK_DEFAULT &&
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spare_stack->guardsize == _pthread_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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}
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