+++ /dev/null
-/*
- * 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 2.1 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 "hw/core/cpu.h"
-#include "sysemu/cpus.h"
-#include "qemu/lockable.h"
-
-static QemuMutex qemu_cpu_list_lock;
-static QemuCond exclusive_cond;
-static QemuCond exclusive_resume;
-static QemuCond qemu_work_cond;
-
-/* >= 1 if a thread is inside start_exclusive/end_exclusive. Written
- * under qemu_cpu_list_lock, read with atomic operations.
- */
-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 max_cpu_index = 0;
-
- cpu_index_auto_assigned = true;
- CPU_FOREACH(some_cpu) {
- if (some_cpu->cpu_index >= max_cpu_index) {
- max_cpu_index = some_cpu->cpu_index + 1;
- }
- }
- return max_cpu_index;
-}
-
-CPUTailQ cpus = QTAILQ_HEAD_INITIALIZER(cpus);
-static unsigned int cpu_list_generation_id;
-
-unsigned int cpu_list_generation_id_get(void)
-{
- return cpu_list_generation_id;
-}
-
-void cpu_list_add(CPUState *cpu)
-{
- QEMU_LOCK_GUARD(&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_RCU(&cpus, cpu, node);
- cpu_list_generation_id++;
-}
-
-void cpu_list_remove(CPUState *cpu)
-{
- QEMU_LOCK_GUARD(&qemu_cpu_list_lock);
- if (!QTAILQ_IN_USE(cpu, node)) {
- /* there is nothing to undo since cpu_exec_init() hasn't been called */
- return;
- }
-
- QTAILQ_REMOVE_RCU(&cpus, cpu, node);
- cpu->cpu_index = UNASSIGNED_CPU_INDEX;
- cpu_list_generation_id++;
-}
-
-CPUState *qemu_get_cpu(int index)
-{
- CPUState *cpu;
-
- CPU_FOREACH(cpu) {
- if (cpu->cpu_index == index) {
- return cpu;
- }
- }
-
- return NULL;
-}
-
-/* current CPU in the current thread. It is only valid inside cpu_exec() */
-__thread CPUState *current_cpu;
-
-struct qemu_work_item {
- QSIMPLEQ_ENTRY(qemu_work_item) node;
- run_on_cpu_func func;
- run_on_cpu_data data;
- bool free, exclusive, done;
-};
-
-static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
-{
- qemu_mutex_lock(&cpu->work_mutex);
- QSIMPLEQ_INSERT_TAIL(&cpu->work_list, wi, node);
- 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, run_on_cpu_data 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 (!qatomic_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, run_on_cpu_data data)
-{
- struct qemu_work_item *wi;
-
- wi = g_new0(struct qemu_work_item, 1);
- 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;
- int running_cpus;
-
- qemu_mutex_lock(&qemu_cpu_list_lock);
- exclusive_idle();
-
- /* Make all other cpus stop executing. */
- qatomic_set(&pending_cpus, 1);
-
- /* Write pending_cpus before reading other_cpu->running. */
- smp_mb();
- running_cpus = 0;
- CPU_FOREACH(other_cpu) {
- if (qatomic_read(&other_cpu->running)) {
- other_cpu->has_waiter = true;
- running_cpus++;
- qemu_cpu_kick(other_cpu);
- }
- }
-
- qatomic_set(&pending_cpus, running_cpus + 1);
- 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);
-
- current_cpu->in_exclusive_context = true;
-}
-
-/* Finish an exclusive operation. */
-void end_exclusive(void)
-{
- current_cpu->in_exclusive_context = false;
-
- qemu_mutex_lock(&qemu_cpu_list_lock);
- qatomic_set(&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)
-{
- qatomic_set(&cpu->running, true);
-
- /* Write cpu->running before reading pending_cpus. */
- smp_mb();
-
- /* 1. start_exclusive saw cpu->running == true and pending_cpus >= 1.
- * After taking the lock we'll see cpu->has_waiter == true and run---not
- * for long because start_exclusive kicked us. cpu_exec_end will
- * decrement pending_cpus and signal the waiter.
- *
- * 2. start_exclusive saw cpu->running == false but pending_cpus >= 1.
- * This includes the case when an exclusive item is running now.
- * Then we'll see cpu->has_waiter == false and wait for the item to
- * complete.
- *
- * 3. pending_cpus == 0. Then start_exclusive is definitely going to
- * see cpu->running == true, and it will kick the CPU.
- */
- if (unlikely(qatomic_read(&pending_cpus))) {
- QEMU_LOCK_GUARD(&qemu_cpu_list_lock);
- if (!cpu->has_waiter) {
- /* Not counted in pending_cpus, let the exclusive item
- * run. Since we have the lock, just set cpu->running to true
- * while holding it; no need to check pending_cpus again.
- */
- qatomic_set(&cpu->running, false);
- exclusive_idle();
- /* Now pending_cpus is zero. */
- qatomic_set(&cpu->running, true);
- } else {
- /* Counted in pending_cpus, go ahead and release the
- * waiter at cpu_exec_end.
- */
- }
- }
-}
-
-/* Mark cpu as not executing, and release pending exclusive ops. */
-void cpu_exec_end(CPUState *cpu)
-{
- qatomic_set(&cpu->running, false);
-
- /* Write cpu->running before reading pending_cpus. */
- smp_mb();
-
- /* 1. start_exclusive saw cpu->running == true. Then it will increment
- * pending_cpus and wait for exclusive_cond. After taking the lock
- * we'll see cpu->has_waiter == true.
- *
- * 2. start_exclusive saw cpu->running == false but here pending_cpus >= 1.
- * This includes the case when an exclusive item started after setting
- * cpu->running to false and before we read pending_cpus. Then we'll see
- * cpu->has_waiter == false and not touch pending_cpus. The next call to
- * cpu_exec_start will run exclusive_idle if still necessary, thus waiting
- * for the item to complete.
- *
- * 3. pending_cpus == 0. Then start_exclusive is definitely going to
- * see cpu->running == false, and it can ignore this CPU until the
- * next cpu_exec_start.
- */
- if (unlikely(qatomic_read(&pending_cpus))) {
- QEMU_LOCK_GUARD(&qemu_cpu_list_lock);
- if (cpu->has_waiter) {
- cpu->has_waiter = false;
- qatomic_set(&pending_cpus, pending_cpus - 1);
- if (pending_cpus == 1) {
- qemu_cond_signal(&exclusive_cond);
- }
- }
- }
-}
-
-void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func,
- run_on_cpu_data data)
-{
- struct qemu_work_item *wi;
-
- wi = g_new0(struct qemu_work_item, 1);
- 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;
-
- qemu_mutex_lock(&cpu->work_mutex);
- if (QSIMPLEQ_EMPTY(&cpu->work_list)) {
- qemu_mutex_unlock(&cpu->work_mutex);
- return;
- }
- while (!QSIMPLEQ_EMPTY(&cpu->work_list)) {
- wi = QSIMPLEQ_FIRST(&cpu->work_list);
- QSIMPLEQ_REMOVE_HEAD(&cpu->work_list, node);
- 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 {
- qatomic_mb_set(&wi->done, true);
- }
- }
- qemu_mutex_unlock(&cpu->work_mutex);
- qemu_cond_broadcast(&qemu_work_cond);
-}
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