diff options
Diffstat (limited to 'coroutine-ucontext.c')
| -rw-r--r-- | coroutine-ucontext.c | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/coroutine-ucontext.c b/coroutine-ucontext.c new file mode 100644 index 0000000000..41c2379a2a --- /dev/null +++ b/coroutine-ucontext.c @@ -0,0 +1,230 @@ +/* + * 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, +}; + +typedef struct { + Coroutine base; + void *stack; + jmp_buf env; +} CoroutineUContext; + +/** + * Per-thread coroutine bookkeeping + */ +typedef struct { + /** Currently executing coroutine */ + Coroutine *current; + + /** Free list to speed up creation */ + QLIST_HEAD(, Coroutine) pool; + unsigned int pool_size; + + /** 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 = qemu_mallocz(sizeof(*s)); + s->current = &s->leader.base; + QLIST_INIT(&s->pool); + pthread_setspecific(thread_state_key, s); + } + return s; +} + +static void qemu_coroutine_thread_cleanup(void *opaque) +{ + CoroutineThreadState *s = opaque; + Coroutine *co; + Coroutine *tmp; + + QLIST_FOREACH_SAFE(co, &s->pool, pool_next, tmp) { + qemu_free(DO_UPCAST(CoroutineUContext, base, co)->stack); + qemu_free(co); + } + qemu_free(s); +} + +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; + + /* 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 = qemu_mallocz(sizeof(*co)); + co->stack = qemu_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) +{ + CoroutineThreadState *s = coroutine_get_thread_state(); + Coroutine *co; + + co = QLIST_FIRST(&s->pool); + if (co) { + QLIST_REMOVE(co, pool_next); + s->pool_size--; + } else { + co = coroutine_new(); + } + return co; +} + +void qemu_coroutine_delete(Coroutine *co_) +{ + CoroutineThreadState *s = coroutine_get_thread_state(); + CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_); + + if (s->pool_size < POOL_MAX_SIZE) { + QLIST_INSERT_HEAD(&s->pool, &co->base, pool_next); + co->base.caller = NULL; + s->pool_size++; + return; + } + + qemu_free(co->stack); + qemu_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; +} |