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