root / coroutine-ucontext.c @ a8a00822
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/*
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* ucontext coroutine initialization code
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*
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* Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
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* Copyright (C) 2011 Kevin Wolf <kwolf@redhat.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.0 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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/* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
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#ifdef _FORTIFY_SOURCE
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#undef _FORTIFY_SOURCE
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#endif
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#include <stdlib.h> |
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#include <setjmp.h> |
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#include <stdint.h> |
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#include <pthread.h> |
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#include <ucontext.h> |
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#include "qemu-common.h" |
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#include "qemu-coroutine-int.h" |
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enum {
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/* Maximum free pool size prevents holding too many freed coroutines */
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POOL_MAX_SIZE = 64,
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}; |
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typedef struct { |
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Coroutine base; |
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void *stack;
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jmp_buf env; |
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} CoroutineUContext; |
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/**
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* Per-thread coroutine bookkeeping
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*/
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typedef struct { |
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/** Currently executing coroutine */
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Coroutine *current; |
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/** Free list to speed up creation */
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QLIST_HEAD(, Coroutine) pool; |
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unsigned int pool_size; |
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/** The default coroutine */
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CoroutineUContext leader; |
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} CoroutineThreadState; |
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static pthread_key_t thread_state_key;
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/*
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* va_args to makecontext() must be type 'int', so passing
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* the pointer we need may require several int args. This
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* union is a quick hack to let us do that
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*/
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union cc_arg {
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void *p;
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int i[2]; |
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}; |
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static CoroutineThreadState *coroutine_get_thread_state(void) |
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{ |
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CoroutineThreadState *s = pthread_getspecific(thread_state_key); |
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if (!s) {
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s = g_malloc0(sizeof(*s));
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s->current = &s->leader.base; |
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QLIST_INIT(&s->pool); |
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pthread_setspecific(thread_state_key, s); |
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} |
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return s;
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} |
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static void qemu_coroutine_thread_cleanup(void *opaque) |
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{ |
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CoroutineThreadState *s = opaque; |
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Coroutine *co; |
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Coroutine *tmp; |
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QLIST_FOREACH_SAFE(co, &s->pool, pool_next, tmp) { |
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g_free(DO_UPCAST(CoroutineUContext, base, co)->stack); |
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g_free(co); |
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} |
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g_free(s); |
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} |
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static void __attribute__((constructor)) coroutine_init(void) |
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{ |
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int ret;
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ret = pthread_key_create(&thread_state_key, qemu_coroutine_thread_cleanup); |
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if (ret != 0) { |
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fprintf(stderr, "unable to create leader key: %s\n", strerror(errno));
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abort(); |
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} |
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} |
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static void coroutine_trampoline(int i0, int i1) |
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{ |
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union cc_arg arg;
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CoroutineUContext *self; |
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Coroutine *co; |
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arg.i[0] = i0;
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arg.i[1] = i1;
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self = arg.p; |
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co = &self->base; |
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/* Initialize longjmp environment and switch back the caller */
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if (!setjmp(self->env)) {
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longjmp(*(jmp_buf *)co->entry_arg, 1);
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} |
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while (true) { |
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co->entry(co->entry_arg); |
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qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE); |
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} |
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} |
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static Coroutine *coroutine_new(void) |
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{ |
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const size_t stack_size = 1 << 20; |
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CoroutineUContext *co; |
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ucontext_t old_uc, uc; |
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jmp_buf old_env; |
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union cc_arg arg = {0}; |
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/* The ucontext functions preserve signal masks which incurs a system call
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* overhead. setjmp()/longjmp() does not preserve signal masks but only
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* works on the current stack. Since we need a way to create and switch to
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* a new stack, use the ucontext functions for that but setjmp()/longjmp()
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* for everything else.
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*/
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if (getcontext(&uc) == -1) { |
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abort(); |
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} |
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co = g_malloc0(sizeof(*co));
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co->stack = g_malloc(stack_size); |
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co->base.entry_arg = &old_env; /* stash away our jmp_buf */
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uc.uc_link = &old_uc; |
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uc.uc_stack.ss_sp = co->stack; |
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uc.uc_stack.ss_size = stack_size; |
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uc.uc_stack.ss_flags = 0;
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arg.p = co; |
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makecontext(&uc, (void (*)(void))coroutine_trampoline, |
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2, arg.i[0], arg.i[1]); |
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/* swapcontext() in, longjmp() back out */
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if (!setjmp(old_env)) {
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swapcontext(&old_uc, &uc); |
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} |
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return &co->base;
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} |
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Coroutine *qemu_coroutine_new(void)
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{ |
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CoroutineThreadState *s = coroutine_get_thread_state(); |
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Coroutine *co; |
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co = QLIST_FIRST(&s->pool); |
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if (co) {
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QLIST_REMOVE(co, pool_next); |
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s->pool_size--; |
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} else {
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co = coroutine_new(); |
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} |
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return co;
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} |
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void qemu_coroutine_delete(Coroutine *co_)
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{ |
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CoroutineThreadState *s = coroutine_get_thread_state(); |
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CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_); |
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if (s->pool_size < POOL_MAX_SIZE) {
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QLIST_INSERT_HEAD(&s->pool, &co->base, pool_next); |
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co->base.caller = NULL;
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s->pool_size++; |
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return;
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} |
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g_free(co->stack); |
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g_free(co); |
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} |
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CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_, |
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CoroutineAction action) |
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{ |
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CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_); |
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CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_); |
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CoroutineThreadState *s = coroutine_get_thread_state(); |
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int ret;
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s->current = to_; |
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ret = setjmp(from->env); |
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if (ret == 0) { |
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longjmp(to->env, action); |
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} |
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return ret;
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} |
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Coroutine *qemu_coroutine_self(void)
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{ |
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CoroutineThreadState *s = coroutine_get_thread_state(); |
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return s->current;
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} |
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bool qemu_in_coroutine(void) |
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{ |
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CoroutineThreadState *s = pthread_getspecific(thread_state_key); |
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return s && s->current->caller;
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} |