Import QEMU upstream snapshot d2e570c

Upstream: https://gitlab.com/qemu-project/qemu.git

Upstream-Commit: d2e570cc0f97b936902a5b1b86b73c0f5998b475

iothread.c

@@ -0,0 +1,429 @@
+/*
+ * Event loop thread
+ *
+ * Copyright Red Hat Inc., 2013, 2020
+ *
+ * Authors:
+ *  Stefan Hajnoczi   <[email protected]>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qom/object.h"
+#include "qom/object_interfaces.h"
+#include "qemu/module.h"
+#include "qemu/aio.h"
+#include "block/block.h"
+#include "system/event-loop-base.h"
+#include "system/iothread.h"
+#include "qapi/error.h"
+#include "qapi/qapi-commands-misc.h"
+#include "qemu/error-report.h"
+#include "qemu/rcu.h"
+#include "qemu/main-loop.h"
+
+static void *iothread_run(void *opaque)
+{
+    IOThread *iothread = opaque;
+
+    rcu_register_thread();
+    /*
+     * g_main_context_push_thread_default() must be called before anything
+     * in this new thread uses glib.
+     */
+    g_main_context_push_thread_default(iothread->worker_context);
+    qemu_set_current_aio_context(iothread->ctx);
+    iothread->thread_id = qemu_get_thread_id();
+    qemu_sem_post(&iothread->init_done_sem);
+
+    while (iothread->running) {
+        /*
+         * Note: from functional-wise the g_main_loop_run() below can
+         * already cover the aio_poll() events, but we can't run the
+         * main loop unconditionally because explicit aio_poll() here
+         * is faster than g_main_loop_run() when we do not need the
+         * gcontext at all (e.g., pure block layer iothreads).  In
+         * other words, when we want to run the gcontext with the
+         * iothread we need to pay some performance for functionality.
+         */
+        aio_poll(iothread->ctx, true);
+
+        /*
+         * We must check the running state again in case it was
+         * changed in previous aio_poll()
+         */
+        if (iothread->running && qatomic_read(&iothread->run_gcontext)) {
+            g_main_loop_run(iothread->main_loop);
+        }
+    }
+
+    g_main_context_pop_thread_default(iothread->worker_context);
+    rcu_unregister_thread();
+    return NULL;
+}
+
+/* Runs in iothread_run() thread */
+static void iothread_stop_bh(void *opaque)
+{
+    IOThread *iothread = opaque;
+
+    iothread->running = false; /* stop iothread_run() */
+
+    if (iothread->main_loop) {
+        g_main_loop_quit(iothread->main_loop);
+    }
+}
+
+void iothread_stop(IOThread *iothread)
+{
+    if (!iothread->ctx || iothread->stopping) {
+        return;
+    }
+    iothread->stopping = true;
+    aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
+    qemu_thread_join(&iothread->thread);
+}
+
+static void iothread_instance_init(Object *obj)
+{
+    IOThread *iothread = IOTHREAD(obj);
+
+    iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
+    iothread->poll_grow = IOTHREAD_POLL_GROW_DEFAULT;
+    iothread->poll_shrink = IOTHREAD_POLL_SHRINK_DEFAULT;
+    iothread->poll_weight = IOTHREAD_POLL_WEIGHT_DEFAULT;
+
+    iothread->thread_id = -1;
+    qemu_sem_init(&iothread->init_done_sem, 0);
+    /* By default, we don't run gcontext */
+    qatomic_set(&iothread->run_gcontext, 0);
+}
+
+static void iothread_instance_finalize(Object *obj)
+{
+    IOThread *iothread = IOTHREAD(obj);
+
+    iothread_stop(iothread);
+
+    /*
+     * Before glib2 2.33.10, there is a glib2 bug that GSource context
+     * pointer may not be cleared even if the context has already been
+     * destroyed (while it should).  Here let's free the AIO context
+     * earlier to bypass that glib bug.
+     *
+     * We can remove this comment after the minimum supported glib2
+     * version boosts to 2.33.10.  Before that, let's free the
+     * GSources first before destroying any GMainContext.
+     */
+    if (iothread->ctx) {
+        aio_context_unref(iothread->ctx);
+        iothread->ctx = NULL;
+    }
+    if (iothread->worker_context) {
+        g_main_context_unref(iothread->worker_context);
+        iothread->worker_context = NULL;
+        g_main_loop_unref(iothread->main_loop);
+        iothread->main_loop = NULL;
+    }
+    qemu_sem_destroy(&iothread->init_done_sem);
+}
+
+static void iothread_init_gcontext(IOThread *iothread, const char *thread_name)
+{
+    GSource *source;
+    g_autofree char *name = g_strdup_printf("%s aio-context", thread_name);
+
+    iothread->worker_context = g_main_context_new();
+    source = aio_get_g_source(iothread_get_aio_context(iothread));
+    g_source_set_name(source, name);
+    g_source_attach(source, iothread->worker_context);
+    g_source_unref(source);
+    iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);
+}
+
+static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp)
+{
+    ERRP_GUARD();
+    IOThread *iothread = IOTHREAD(base);
+
+    if (!iothread->ctx) {
+        return;
+    }
+
+    aio_context_set_poll_params(iothread->ctx,
+                                iothread->poll_max_ns,
+                                iothread->poll_grow,
+                                iothread->poll_shrink,
+                                iothread->poll_weight,
+                                errp);
+    if (*errp) {
+        return;
+    }
+
+    aio_context_set_aio_params(iothread->ctx,
+                               iothread->parent_obj.aio_max_batch);
+
+    aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min,
+                                       base->thread_pool_max, errp);
+}
+
+
+static void iothread_init(EventLoopBase *base, Error **errp)
+{
+    Error *local_error = NULL;
+    IOThread *iothread = IOTHREAD(base);
+    g_autofree char *thread_name = NULL;
+
+    iothread->stopping = false;
+    iothread->running = true;
+    iothread->ctx = aio_context_new(errp);
+    if (!iothread->ctx) {
+        return;
+    }
+
+    thread_name = g_strdup_printf("IO %s",
+                        object_get_canonical_path_component(OBJECT(base)));
+
+    /*
+     * Init one GMainContext for the iothread unconditionally, even if
+     * it's not used
+     */
+    iothread_init_gcontext(iothread, thread_name);
+
+    iothread_set_aio_context_params(base, &local_error);
+    if (local_error) {
+        error_propagate(errp, local_error);
+        aio_context_unref(iothread->ctx);
+        iothread->ctx = NULL;
+        return;
+    }
+
+    /* This assumes we are called from a thread with useful CPU affinity for us
+     * to inherit.
+     */
+    qemu_thread_create(&iothread->thread, thread_name, iothread_run,
+                       iothread, QEMU_THREAD_JOINABLE);
+
+    /* Wait for initialization to complete */
+    while (iothread->thread_id == -1) {
+        qemu_sem_wait(&iothread->init_done_sem);
+    }
+}
+
+typedef struct {
+    const char *name;
+    ptrdiff_t offset; /* field's byte offset in IOThread struct */
+} IOThreadParamInfo;
+
+static IOThreadParamInfo poll_max_ns_info = {
+    "poll-max-ns", offsetof(IOThread, poll_max_ns),
+};
+static IOThreadParamInfo poll_grow_info = {
+    "poll-grow", offsetof(IOThread, poll_grow),
+};
+static IOThreadParamInfo poll_shrink_info = {
+    "poll-shrink", offsetof(IOThread, poll_shrink),
+};
+static IOThreadParamInfo poll_weight_info = {
+    "poll-weight", offsetof(IOThread, poll_weight),
+};
+
+static void iothread_get_param(Object *obj, Visitor *v,
+        const char *name, IOThreadParamInfo *info, Error **errp)
+{
+    IOThread *iothread = IOTHREAD(obj);
+    int64_t *field = (void *)iothread + info->offset;
+
+    visit_type_int64(v, name, field, errp);
+}
+
+static bool iothread_set_param(Object *obj, Visitor *v,
+        const char *name, IOThreadParamInfo *info, Error **errp)
+{
+    IOThread *iothread = IOTHREAD(obj);
+    int64_t *field = (void *)iothread + info->offset;
+    int64_t value;
+
+    if (!visit_type_int64(v, name, &value, errp)) {
+        return false;
+    }
+
+    if (info->offset == offsetof(IOThread, poll_weight)) {
+        if (value < 0 || value > 63) {
+            error_setg(errp, "%s value must be in range [0, 63]",
+                       info->name);
+            return false;
+        }
+    } else if (value < 0) {
+        error_setg(errp, "%s value must be in range [0, %" PRId64 "]",
+                   info->name, INT64_MAX);
+        return false;
+    }
+
+    if (value == 0) {
+        if (info->offset == offsetof(IOThread, poll_grow)) {
+            *field = IOTHREAD_POLL_GROW_DEFAULT;
+        } else if (info->offset == offsetof(IOThread, poll_shrink)) {
+            *field = IOTHREAD_POLL_SHRINK_DEFAULT;
+        } else if (info->offset == offsetof(IOThread, poll_weight)) {
+            *field = IOTHREAD_POLL_WEIGHT_DEFAULT;
+        } else {
+            *field = value;
+        }
+    } else {
+        *field = value;
+    }
+
+    return true;
+}
+
+static void iothread_get_poll_param(Object *obj, Visitor *v,
+        const char *name, void *opaque, Error **errp)
+{
+    IOThreadParamInfo *info = opaque;
+
+    iothread_get_param(obj, v, name, info, errp);
+}
+
+static void iothread_set_poll_param(Object *obj, Visitor *v,
+        const char *name, void *opaque, Error **errp)
+{
+    IOThread *iothread = IOTHREAD(obj);
+    IOThreadParamInfo *info = opaque;
+
+    if (!iothread_set_param(obj, v, name, info, errp)) {
+        return;
+    }
+
+    if (iothread->ctx) {
+        aio_context_set_poll_params(iothread->ctx,
+                                    iothread->poll_max_ns,
+                                    iothread->poll_grow,
+                                    iothread->poll_shrink,
+                                    iothread->poll_weight,
+                                    errp);
+    }
+}
+
+static void iothread_class_init(ObjectClass *klass, const void *class_data)
+{
+    EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass);
+
+    bc->init = iothread_init;
+    bc->update_params = iothread_set_aio_context_params;
+
+    object_class_property_add(klass, "poll-max-ns", "int",
+                              iothread_get_poll_param,
+                              iothread_set_poll_param,
+                              NULL, &poll_max_ns_info);
+    object_class_property_add(klass, "poll-grow", "int",
+                              iothread_get_poll_param,
+                              iothread_set_poll_param,
+                              NULL, &poll_grow_info);
+    object_class_property_add(klass, "poll-shrink", "int",
+                              iothread_get_poll_param,
+                              iothread_set_poll_param,
+                              NULL, &poll_shrink_info);
+    object_class_property_add(klass, "poll-weight", "int",
+                              iothread_get_poll_param,
+                              iothread_set_poll_param,
+                              NULL, &poll_weight_info);
+}
+
+static const TypeInfo iothread_info = {
+    .name = TYPE_IOTHREAD,
+    .parent = TYPE_EVENT_LOOP_BASE,
+    .class_init = iothread_class_init,
+    .instance_size = sizeof(IOThread),
+    .instance_init = iothread_instance_init,
+    .instance_finalize = iothread_instance_finalize,
+};
+
+static void iothread_register_types(void)
+{
+    type_register_static(&iothread_info);
+}
+
+type_init(iothread_register_types)
+
+char *iothread_get_id(IOThread *iothread)
+{
+    return g_strdup(object_get_canonical_path_component(OBJECT(iothread)));
+}
+
+AioContext *iothread_get_aio_context(IOThread *iothread)
+{
+    return iothread->ctx;
+}
+
+static int query_one_iothread(Object *object, void *opaque)
+{
+    IOThreadInfoList ***tail = opaque;
+    IOThreadInfo *info;
+    IOThread *iothread;
+
+    iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
+    if (!iothread) {
+        return 0;
+    }
+
+    info = g_new0(IOThreadInfo, 1);
+    info->id = iothread_get_id(iothread);
+    info->thread_id = iothread->thread_id;
+    info->poll_max_ns = iothread->poll_max_ns;
+    info->poll_grow = iothread->poll_grow;
+    info->poll_shrink = iothread->poll_shrink;
+    info->poll_weight = iothread->poll_weight;
+    info->aio_max_batch = iothread->parent_obj.aio_max_batch;
+
+    QAPI_LIST_APPEND(*tail, info);
+    return 0;
+}
+
+IOThreadInfoList *qmp_query_iothreads(Error **errp)
+{
+    IOThreadInfoList *head = NULL;
+    IOThreadInfoList **prev = &head;
+    Object *container = object_get_objects_root();
+
+    object_child_foreach(container, query_one_iothread, &prev);
+    return head;
+}
+
+GMainContext *iothread_get_g_main_context(IOThread *iothread)
+{
+    qatomic_set(&iothread->run_gcontext, 1);
+    aio_notify(iothread->ctx);
+    return iothread->worker_context;
+}
+
+IOThread *iothread_create(const char *id, Error **errp)
+{
+    Object *obj;
+
+    obj = object_new_with_props(TYPE_IOTHREAD,
+                                object_get_internal_root(),
+                                id, errp, NULL);
+
+    return IOTHREAD(obj);
+}
+
+void iothread_destroy(IOThread *iothread)
+{
+    object_unparent(OBJECT(iothread));
+}
+
+/* Lookup IOThread by its id.  Only finds user-created objects, not internal
+ * iothread_create() objects. */
+IOThread *iothread_by_id(const char *id)
+{
+    return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
+}
+
+bool qemu_in_iothread(void)
+{
+    return qemu_get_current_aio_context() != qemu_get_aio_context();
+}