qemu/cpus-common.c

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/*
* CPU thread main loop - common bits for user and system mode emulation
*
* Copyright (c) 2003-2005 Fabrice Bellard
*
* 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 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/>.
*/
#include "qemu/osdep.h"
#include "qemu/main-loop.h"
#include "exec/cpu-common.h"
#include "qom/cpu.h"
#include "sysemu/cpus.h"
static QemuMutex qemu_cpu_list_lock;
static QemuCond exclusive_cond;
static QemuCond exclusive_resume;
static QemuCond qemu_work_cond;
static int pending_cpus;
void qemu_init_cpu_list(void)
{
/* This is needed because qemu_init_cpu_list is also called by the
* child process in a fork. */
pending_cpus = 0;
qemu_mutex_init(&qemu_cpu_list_lock);
qemu_cond_init(&exclusive_cond);
qemu_cond_init(&exclusive_resume);
qemu_cond_init(&qemu_work_cond);
}
void cpu_list_lock(void)
{
qemu_mutex_lock(&qemu_cpu_list_lock);
}
void cpu_list_unlock(void)
{
qemu_mutex_unlock(&qemu_cpu_list_lock);
}
static bool cpu_index_auto_assigned;
static int cpu_get_free_index(void)
{
CPUState *some_cpu;
int cpu_index = 0;
cpu_index_auto_assigned = true;
CPU_FOREACH(some_cpu) {
cpu_index++;
}
return cpu_index;
}
static void finish_safe_work(CPUState *cpu)
{
cpu_exec_start(cpu);
cpu_exec_end(cpu);
}
void cpu_list_add(CPUState *cpu)
{
qemu_mutex_lock(&qemu_cpu_list_lock);
if (cpu->cpu_index == UNASSIGNED_CPU_INDEX) {
cpu->cpu_index = cpu_get_free_index();
assert(cpu->cpu_index != UNASSIGNED_CPU_INDEX);
} else {
assert(!cpu_index_auto_assigned);
}
QTAILQ_INSERT_TAIL(&cpus, cpu, node);
qemu_mutex_unlock(&qemu_cpu_list_lock);
finish_safe_work(cpu);
}
void cpu_list_remove(CPUState *cpu)
{
qemu_mutex_lock(&qemu_cpu_list_lock);
if (!QTAILQ_IN_USE(cpu, node)) {
/* there is nothing to undo since cpu_exec_init() hasn't been called */
qemu_mutex_unlock(&qemu_cpu_list_lock);
return;
}
assert(!(cpu_index_auto_assigned && cpu != QTAILQ_LAST(&cpus, CPUTailQ)));
QTAILQ_REMOVE(&cpus, cpu, node);
cpu->cpu_index = UNASSIGNED_CPU_INDEX;
qemu_mutex_unlock(&qemu_cpu_list_lock);
}
struct qemu_work_item {
struct qemu_work_item *next;
run_on_cpu_func func;
void *data;
bool free, exclusive, done;
};
static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
{
qemu_mutex_lock(&cpu->work_mutex);
if (cpu->queued_work_first == NULL) {
cpu->queued_work_first = wi;
} else {
cpu->queued_work_last->next = wi;
}
cpu->queued_work_last = wi;
wi->next = NULL;
wi->done = false;
qemu_mutex_unlock(&cpu->work_mutex);
qemu_cpu_kick(cpu);
}
void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data,
QemuMutex *mutex)
{
struct qemu_work_item wi;
if (qemu_cpu_is_self(cpu)) {
func(cpu, data);
return;
}
wi.func = func;
wi.data = data;
wi.done = false;
wi.free = false;
wi.exclusive = false;
queue_work_on_cpu(cpu, &wi);
while (!atomic_mb_read(&wi.done)) {
CPUState *self_cpu = current_cpu;
qemu_cond_wait(&qemu_work_cond, mutex);
current_cpu = self_cpu;
}
}
void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
{
struct qemu_work_item *wi;
wi = g_malloc0(sizeof(struct qemu_work_item));
wi->func = func;
wi->data = data;
wi->free = true;
queue_work_on_cpu(cpu, wi);
}
/* Wait for pending exclusive operations to complete. The CPU list lock
must be held. */
static inline void exclusive_idle(void)
{
while (pending_cpus) {
qemu_cond_wait(&exclusive_resume, &qemu_cpu_list_lock);
}
}
/* Start an exclusive operation.
Must only be called from outside cpu_exec. */
void start_exclusive(void)
{
CPUState *other_cpu;
qemu_mutex_lock(&qemu_cpu_list_lock);
exclusive_idle();
/* Make all other cpus stop executing. */
pending_cpus = 1;
CPU_FOREACH(other_cpu) {
if (other_cpu->running) {
pending_cpus++;
qemu_cpu_kick(other_cpu);
}
}
while (pending_cpus > 1) {
qemu_cond_wait(&exclusive_cond, &qemu_cpu_list_lock);
}
/* Can release mutex, no one will enter another exclusive
* section until end_exclusive resets pending_cpus to 0.
*/
qemu_mutex_unlock(&qemu_cpu_list_lock);
}
/* Finish an exclusive operation. */
void end_exclusive(void)
{
qemu_mutex_lock(&qemu_cpu_list_lock);
pending_cpus = 0;
qemu_cond_broadcast(&exclusive_resume);
qemu_mutex_unlock(&qemu_cpu_list_lock);
}
/* Wait for exclusive ops to finish, and begin cpu execution. */
void cpu_exec_start(CPUState *cpu)
{
qemu_mutex_lock(&qemu_cpu_list_lock);
exclusive_idle();
cpu->running = true;
qemu_mutex_unlock(&qemu_cpu_list_lock);
}
/* Mark cpu as not executing, and release pending exclusive ops. */
void cpu_exec_end(CPUState *cpu)
{
qemu_mutex_lock(&qemu_cpu_list_lock);
cpu->running = false;
if (pending_cpus > 1) {
pending_cpus--;
if (pending_cpus == 1) {
qemu_cond_signal(&exclusive_cond);
}
}
qemu_mutex_unlock(&qemu_cpu_list_lock);
}
void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
{
struct qemu_work_item *wi;
wi = g_malloc0(sizeof(struct qemu_work_item));
wi->func = func;
wi->data = data;
wi->free = true;
wi->exclusive = true;
queue_work_on_cpu(cpu, wi);
}
void process_queued_cpu_work(CPUState *cpu)
{
struct qemu_work_item *wi;
if (cpu->queued_work_first == NULL) {
return;
}
qemu_mutex_lock(&cpu->work_mutex);
while (cpu->queued_work_first != NULL) {
wi = cpu->queued_work_first;
cpu->queued_work_first = wi->next;
if (!cpu->queued_work_first) {
cpu->queued_work_last = NULL;
}
qemu_mutex_unlock(&cpu->work_mutex);
if (wi->exclusive) {
/* Running work items outside the BQL avoids the following deadlock:
* 1) start_exclusive() is called with the BQL taken while another
* CPU is running; 2) cpu_exec in the other CPU tries to takes the
* BQL, so it goes to sleep; start_exclusive() is sleeping too, so
* neither CPU can proceed.
*/
qemu_mutex_unlock_iothread();
start_exclusive();
wi->func(cpu, wi->data);
end_exclusive();
qemu_mutex_lock_iothread();
} else {
wi->func(cpu, wi->data);
}
qemu_mutex_lock(&cpu->work_mutex);
if (wi->free) {
g_free(wi);
} else {
atomic_mb_set(&wi->done, true);
}
}
qemu_mutex_unlock(&cpu->work_mutex);
qemu_cond_broadcast(&qemu_work_cond);
}