--- /dev/null
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu-common.h"
+#include "block/aio.h"
+#include "block/thread-pool.h"
+#include "qemu/main-loop.h"
+#include "qemu/atomic.h"
+
+/***********************************************************/
+/* bottom halves (can be seen as timers which expire ASAP) */
+
+struct QEMUBH {
+ AioContext *ctx;
+ QEMUBHFunc *cb;
+ void *opaque;
+ QEMUBH *next;
+ bool scheduled;
+ bool idle;
+ bool deleted;
+};
+
+QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
+{
+ QEMUBH *bh;
+ bh = g_new(QEMUBH, 1);
+ *bh = (QEMUBH){
+ .ctx = ctx,
+ .cb = cb,
+ .opaque = opaque,
+ };
+ qemu_mutex_lock(&ctx->bh_lock);
+ bh->next = ctx->first_bh;
+ /* Make sure that the members are ready before putting bh into list */
+ smp_wmb();
+ ctx->first_bh = bh;
+ qemu_mutex_unlock(&ctx->bh_lock);
+ return bh;
+}
+
+/* Multiple occurrences of aio_bh_poll cannot be called concurrently */
+int aio_bh_poll(AioContext *ctx)
+{
+ QEMUBH *bh, **bhp, *next;
+ int ret;
+
+ ctx->walking_bh++;
+
+ ret = 0;
+ for (bh = ctx->first_bh; bh; bh = next) {
+ /* Make sure that fetching bh happens before accessing its members */
+ smp_read_barrier_depends();
+ next = bh->next;
+ /* The atomic_xchg is paired with the one in qemu_bh_schedule. The
+ * implicit memory barrier ensures that the callback sees all writes
+ * done by the scheduling thread. It also ensures that the scheduling
+ * thread sees the zero before bh->cb has run, and thus will call
+ * aio_notify again if necessary.
+ */
+ if (!bh->deleted && atomic_xchg(&bh->scheduled, 0)) {
+ /* Idle BHs and the notify BH don't count as progress */
+ if (!bh->idle && bh != ctx->notify_dummy_bh) {
+ ret = 1;
+ }
+ bh->idle = 0;
+ bh->cb(bh->opaque);
+ }
+ }
+
+ ctx->walking_bh--;
+
+ /* remove deleted bhs */
+ if (!ctx->walking_bh) {
+ qemu_mutex_lock(&ctx->bh_lock);
+ bhp = &ctx->first_bh;
+ while (*bhp) {
+ bh = *bhp;
+ if (bh->deleted) {
+ *bhp = bh->next;
+ g_free(bh);
+ } else {
+ bhp = &bh->next;
+ }
+ }
+ qemu_mutex_unlock(&ctx->bh_lock);
+ }
+
+ return ret;
+}
+
+void qemu_bh_schedule_idle(QEMUBH *bh)
+{
+ bh->idle = 1;
+ /* Make sure that idle & any writes needed by the callback are done
+ * before the locations are read in the aio_bh_poll.
+ */
+ atomic_mb_set(&bh->scheduled, 1);
+}
+
+void qemu_bh_schedule(QEMUBH *bh)
+{
+ AioContext *ctx;
+
+ ctx = bh->ctx;
+ bh->idle = 0;
+ /* The memory barrier implicit in atomic_xchg makes sure that:
+ * 1. idle & any writes needed by the callback are done before the
+ * locations are read in the aio_bh_poll.
+ * 2. ctx is loaded before scheduled is set and the callback has a chance
+ * to execute.
+ */
+ if (atomic_xchg(&bh->scheduled, 1) == 0) {
+ aio_notify(ctx);
+ }
+}
+
+
+/* This func is async.
+ */
+void qemu_bh_cancel(QEMUBH *bh)
+{
+ bh->scheduled = 0;
+}
+
+/* This func is async.The bottom half will do the delete action at the finial
+ * end.
+ */
+void qemu_bh_delete(QEMUBH *bh)
+{
+ bh->scheduled = 0;
+ bh->deleted = 1;
+}
+
+int64_t
+aio_compute_timeout(AioContext *ctx)
+{
+ int64_t deadline;
+ int timeout = -1;
+ QEMUBH *bh;
+
+ for (bh = ctx->first_bh; bh; bh = bh->next) {
+ if (!bh->deleted && bh->scheduled) {
+ if (bh->idle) {
+ /* idle bottom halves will be polled at least
+ * every 10ms */
+ timeout = 10000000;
+ } else {
+ /* non-idle bottom halves will be executed
+ * immediately */
+ return 0;
+ }
+ }
+ }
+
+ deadline = timerlistgroup_deadline_ns(&ctx->tlg);
+ if (deadline == 0) {
+ return 0;
+ } else {
+ return qemu_soonest_timeout(timeout, deadline);
+ }
+}
+
+static gboolean
+aio_ctx_prepare(GSource *source, gint *timeout)
+{
+ AioContext *ctx = (AioContext *) source;
+
+ atomic_or(&ctx->notify_me, 1);
+
+ /* We assume there is no timeout already supplied */
+ *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
+
+ if (aio_prepare(ctx)) {
+ *timeout = 0;
+ }
+
+ return *timeout == 0;
+}
+
+static gboolean
+aio_ctx_check(GSource *source)
+{
+ AioContext *ctx = (AioContext *) source;
+ QEMUBH *bh;
+
+ atomic_and(&ctx->notify_me, ~1);
+ aio_notify_accept(ctx);
+
+ for (bh = ctx->first_bh; bh; bh = bh->next) {
+ if (!bh->deleted && bh->scheduled) {
+ return true;
+ }
+ }
+ return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
+}
+
+static gboolean
+aio_ctx_dispatch(GSource *source,
+ GSourceFunc callback,
+ gpointer user_data)
+{
+ AioContext *ctx = (AioContext *) source;
+
+ assert(callback == NULL);
+ aio_dispatch(ctx);
+ return true;
+}
+
+static void
+aio_ctx_finalize(GSource *source)
+{
+ AioContext *ctx = (AioContext *) source;
+
+ qemu_bh_delete(ctx->notify_dummy_bh);
+ thread_pool_free(ctx->thread_pool);
+
+ qemu_mutex_lock(&ctx->bh_lock);
+ while (ctx->first_bh) {
+ QEMUBH *next = ctx->first_bh->next;
+
+ /* qemu_bh_delete() must have been called on BHs in this AioContext */
+ assert(ctx->first_bh->deleted);
+
+ g_free(ctx->first_bh);
+ ctx->first_bh = next;
+ }
+ qemu_mutex_unlock(&ctx->bh_lock);
+
+ aio_set_event_notifier(ctx, &ctx->notifier, NULL);
+ event_notifier_cleanup(&ctx->notifier);
+ rfifolock_destroy(&ctx->lock);
+ qemu_mutex_destroy(&ctx->bh_lock);
+ timerlistgroup_deinit(&ctx->tlg);
+}
+
+static GSourceFuncs aio_source_funcs = {
+ aio_ctx_prepare,
+ aio_ctx_check,
+ aio_ctx_dispatch,
+ aio_ctx_finalize
+};
+
+GSource *aio_get_g_source(AioContext *ctx)
+{
+ g_source_ref(&ctx->source);
+ return &ctx->source;
+}
+
+ThreadPool *aio_get_thread_pool(AioContext *ctx)
+{
+ if (!ctx->thread_pool) {
+ ctx->thread_pool = thread_pool_new(ctx);
+ }
+ return ctx->thread_pool;
+}
+
+void aio_notify(AioContext *ctx)
+{
+ /* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs
+ * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
+ */
+ smp_mb();
+ if (ctx->notify_me) {
+ event_notifier_set(&ctx->notifier);
+ atomic_mb_set(&ctx->notified, true);
+ }
+}
+
+void aio_notify_accept(AioContext *ctx)
+{
+ if (atomic_xchg(&ctx->notified, false)) {
+ event_notifier_test_and_clear(&ctx->notifier);
+ }
+}
+
+static void aio_timerlist_notify(void *opaque)
+{
+ aio_notify(opaque);
+}
+
+static void aio_rfifolock_cb(void *opaque)
+{
+ AioContext *ctx = opaque;
+
+ /* Kick owner thread in case they are blocked in aio_poll() */
+ qemu_bh_schedule(ctx->notify_dummy_bh);
+}
+
+static void notify_dummy_bh(void *opaque)
+{
+ /* Do nothing, we were invoked just to force the event loop to iterate */
+}
+
+static void event_notifier_dummy_cb(EventNotifier *e)
+{
+}
+
+AioContext *aio_context_new(Error **errp)
+{
+ int ret;
+ AioContext *ctx;
+ ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
+ ret = event_notifier_init(&ctx->notifier, false);
+ if (ret < 0) {
+ g_source_destroy(&ctx->source);
+ error_setg_errno(errp, -ret, "Failed to initialize event notifier");
+ return NULL;
+ }
+ g_source_set_can_recurse(&ctx->source, true);
+ aio_set_event_notifier(ctx, &ctx->notifier,
+ (EventNotifierHandler *)
+ event_notifier_dummy_cb);
+ ctx->thread_pool = NULL;
+ qemu_mutex_init(&ctx->bh_lock);
+ rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
+ timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
+
+ ctx->notify_dummy_bh = aio_bh_new(ctx, notify_dummy_bh, NULL);
+
+ return ctx;
+}
+
+void aio_context_ref(AioContext *ctx)
+{
+ g_source_ref(&ctx->source);
+}
+
+void aio_context_unref(AioContext *ctx)
+{
+ g_source_unref(&ctx->source);
+}
+
+void aio_context_acquire(AioContext *ctx)
+{
+ rfifolock_lock(&ctx->lock);
+}
+
+void aio_context_release(AioContext *ctx)
+{
+ rfifolock_unlock(&ctx->lock);
+}
Code Review / kvmfornfv.git / blobdiff