1 files changed, 352 insertions, 0 deletions
diff --git a/cpus-common.c b/cpus-common.c
new file mode 100644
index 0000000000..3e114529c9
--- /dev/null
+++ b/cpus-common.c
@@ -0,0 +1,352 @@
+/*
+ * 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;
+
+/* >= 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 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;
+    int running_cpus;
+
+    qemu_mutex_lock(&qemu_cpu_list_lock);
+    exclusive_idle();
+
+    /* Make all other cpus stop executing.  */
+    atomic_set(&pending_cpus, 1);
+
+    /* Write pending_cpus before reading other_cpu->running.  */
+    smp_mb();
+    running_cpus = 0;
+    CPU_FOREACH(other_cpu) {
+        if (atomic_read(&other_cpu->running)) {
+            other_cpu->has_waiter = true;
+            running_cpus++;
+            qemu_cpu_kick(other_cpu);
+        }
+    }
+
+    atomic_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);
+}
+
+/* Finish an exclusive operation.  */
+void end_exclusive(void)
+{
+    qemu_mutex_lock(&qemu_cpu_list_lock);
+    atomic_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)
+{
+    atomic_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(atomic_read(&pending_cpus))) {
+        qemu_mutex_lock(&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.
+             */
+            atomic_set(&cpu->running, false);
+            exclusive_idle();
+            /* Now pending_cpus is zero.  */
+            atomic_set(&cpu->running, true);
+        } else {
+            /* Counted in pending_cpus, go ahead and release the
+             * waiter at cpu_exec_end.
+             */
+        }
+        qemu_mutex_unlock(&qemu_cpu_list_lock);
+    }
+}
+
+/* Mark cpu as not executing, and release pending exclusive ops.  */
+void cpu_exec_end(CPUState *cpu)
+{
+    atomic_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(atomic_read(&pending_cpus))) {
+        qemu_mutex_lock(&qemu_cpu_list_lock);
+        if (cpu->has_waiter) {
+            cpu->has_waiter = false;
+            atomic_set(&pending_cpus, pending_cpus - 1);
+            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);
+}