qemu/coroutine-ucontext.c
Peter Maydell 06d71fa148 configure: Split valgrind test into pragma test and valgrind.h test
Split the configure test that checks for valgrind into two, one
part checking whether we have the gcc pragma to disable unused-but-set
variables, and the other part checking for the existence of valgrind.h.
The first of these has to be compiled with -Werror and the second
does not and shouldn't generate any warnings.

This (a) allows us to enable "make errors in configure tests be
build failures" and (b) enables use of valgrind on systems with
a gcc which doesn't know about -Wunused-but-set-varibale, like
Debian squeeze.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-07-31 20:04:42 +00:00

265 lines
6.4 KiB
C

/*
* 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"
#ifdef CONFIG_VALGRIND_H
#include <valgrind/valgrind.h>
#endif
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;
#ifdef CONFIG_VALGRIND_H
unsigned int valgrind_stack_id;
#endif
} 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;
#ifdef CONFIG_VALGRIND_H
co->valgrind_stack_id =
VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
#endif
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;
}
#ifdef CONFIG_VALGRIND_H
#ifdef CONFIG_PRAGMA_DISABLE_UNUSED_BUT_SET
/* Work around an unused variable in the valgrind.h macro... */
#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
#endif
static inline void valgrind_stack_deregister(CoroutineUContext *co)
{
VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
}
#ifdef CONFIG_PRAGMA_DISABLE_UNUSED_BUT_SET
#pragma GCC diagnostic error "-Wunused-but-set-variable"
#endif
#endif
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;
}
#ifdef CONFIG_VALGRIND_H
valgrind_stack_deregister(co);
#endif
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;
}