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/*
* 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 QSLIST_HEAD(, Coroutine) pool = QSLIST_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;
QSLIST_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 = QSLIST_FIRST(&pool);
if (co) {
QSLIST_REMOVE_HEAD(&pool, 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) {
QSLIST_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;
}
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