virtio-net: separate virtqueue from VirtIONet
[qemu/kevin.git] / coroutine-ucontext.c
bloba9c30e9df412b39cd0f26bfd540469d5390add56
1 /*
2 * ucontext coroutine initialization code
4 * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
5 * Copyright (C) 2011 Kevin Wolf <kwolf@redhat.com>
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.0 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
21 /* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
22 #ifdef _FORTIFY_SOURCE
23 #undef _FORTIFY_SOURCE
24 #endif
25 #include <stdlib.h>
26 #include <setjmp.h>
27 #include <stdint.h>
28 #include <pthread.h>
29 #include <ucontext.h>
30 #include "qemu-common.h"
31 #include "block/coroutine_int.h"
33 #ifdef CONFIG_VALGRIND_H
34 #include <valgrind/valgrind.h>
35 #endif
37 enum {
38 /* Maximum free pool size prevents holding too many freed coroutines */
39 POOL_MAX_SIZE = 64,
42 /** Free list to speed up creation */
43 static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
44 static unsigned int pool_size;
46 typedef struct {
47 Coroutine base;
48 void *stack;
49 jmp_buf env;
51 #ifdef CONFIG_VALGRIND_H
52 unsigned int valgrind_stack_id;
53 #endif
55 } CoroutineUContext;
57 /**
58 * Per-thread coroutine bookkeeping
60 typedef struct {
61 /** Currently executing coroutine */
62 Coroutine *current;
64 /** The default coroutine */
65 CoroutineUContext leader;
66 } CoroutineThreadState;
68 static pthread_key_t thread_state_key;
71 * va_args to makecontext() must be type 'int', so passing
72 * the pointer we need may require several int args. This
73 * union is a quick hack to let us do that
75 union cc_arg {
76 void *p;
77 int i[2];
80 static CoroutineThreadState *coroutine_get_thread_state(void)
82 CoroutineThreadState *s = pthread_getspecific(thread_state_key);
84 if (!s) {
85 s = g_malloc0(sizeof(*s));
86 s->current = &s->leader.base;
87 pthread_setspecific(thread_state_key, s);
89 return s;
92 static void qemu_coroutine_thread_cleanup(void *opaque)
94 CoroutineThreadState *s = opaque;
96 g_free(s);
99 static void __attribute__((destructor)) coroutine_cleanup(void)
101 Coroutine *co;
102 Coroutine *tmp;
104 QSLIST_FOREACH_SAFE(co, &pool, pool_next, tmp) {
105 g_free(DO_UPCAST(CoroutineUContext, base, co)->stack);
106 g_free(co);
110 static void __attribute__((constructor)) coroutine_init(void)
112 int ret;
114 ret = pthread_key_create(&thread_state_key, qemu_coroutine_thread_cleanup);
115 if (ret != 0) {
116 fprintf(stderr, "unable to create leader key: %s\n", strerror(errno));
117 abort();
121 static void coroutine_trampoline(int i0, int i1)
123 union cc_arg arg;
124 CoroutineUContext *self;
125 Coroutine *co;
127 arg.i[0] = i0;
128 arg.i[1] = i1;
129 self = arg.p;
130 co = &self->base;
132 /* Initialize longjmp environment and switch back the caller */
133 if (!setjmp(self->env)) {
134 longjmp(*(jmp_buf *)co->entry_arg, 1);
137 while (true) {
138 co->entry(co->entry_arg);
139 qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
143 static Coroutine *coroutine_new(void)
145 const size_t stack_size = 1 << 20;
146 CoroutineUContext *co;
147 ucontext_t old_uc, uc;
148 jmp_buf old_env;
149 union cc_arg arg = {0};
151 /* The ucontext functions preserve signal masks which incurs a system call
152 * overhead. setjmp()/longjmp() does not preserve signal masks but only
153 * works on the current stack. Since we need a way to create and switch to
154 * a new stack, use the ucontext functions for that but setjmp()/longjmp()
155 * for everything else.
158 if (getcontext(&uc) == -1) {
159 abort();
162 co = g_malloc0(sizeof(*co));
163 co->stack = g_malloc(stack_size);
164 co->base.entry_arg = &old_env; /* stash away our jmp_buf */
166 uc.uc_link = &old_uc;
167 uc.uc_stack.ss_sp = co->stack;
168 uc.uc_stack.ss_size = stack_size;
169 uc.uc_stack.ss_flags = 0;
171 #ifdef CONFIG_VALGRIND_H
172 co->valgrind_stack_id =
173 VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
174 #endif
176 arg.p = co;
178 makecontext(&uc, (void (*)(void))coroutine_trampoline,
179 2, arg.i[0], arg.i[1]);
181 /* swapcontext() in, longjmp() back out */
182 if (!setjmp(old_env)) {
183 swapcontext(&old_uc, &uc);
185 return &co->base;
188 Coroutine *qemu_coroutine_new(void)
190 Coroutine *co;
192 co = QSLIST_FIRST(&pool);
193 if (co) {
194 QSLIST_REMOVE_HEAD(&pool, pool_next);
195 pool_size--;
196 } else {
197 co = coroutine_new();
199 return co;
202 #ifdef CONFIG_VALGRIND_H
203 #ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
204 /* Work around an unused variable in the valgrind.h macro... */
205 #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
206 #endif
207 static inline void valgrind_stack_deregister(CoroutineUContext *co)
209 VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
211 #ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
212 #pragma GCC diagnostic error "-Wunused-but-set-variable"
213 #endif
214 #endif
216 void qemu_coroutine_delete(Coroutine *co_)
218 CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
220 if (pool_size < POOL_MAX_SIZE) {
221 QSLIST_INSERT_HEAD(&pool, &co->base, pool_next);
222 co->base.caller = NULL;
223 pool_size++;
224 return;
227 #ifdef CONFIG_VALGRIND_H
228 valgrind_stack_deregister(co);
229 #endif
231 g_free(co->stack);
232 g_free(co);
235 CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
236 CoroutineAction action)
238 CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
239 CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
240 CoroutineThreadState *s = coroutine_get_thread_state();
241 int ret;
243 s->current = to_;
245 ret = setjmp(from->env);
246 if (ret == 0) {
247 longjmp(to->env, action);
249 return ret;
252 Coroutine *qemu_coroutine_self(void)
254 CoroutineThreadState *s = coroutine_get_thread_state();
256 return s->current;
259 bool qemu_in_coroutine(void)
261 CoroutineThreadState *s = pthread_getspecific(thread_state_key);
263 return s && s->current->caller;