1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232
|
/*
* 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;
}
|