diff options
Diffstat (limited to 'util/async.c')
| -rw-r--r-- | util/async.c | 423 |
1 files changed, 423 insertions, 0 deletions
diff --git a/util/async.c b/util/async.c new file mode 100644 index 0000000000..1fd97e1f15 --- /dev/null +++ b/util/async.c @@ -0,0 +1,423 @@ +/* + * Data plane event loop + * + * Copyright (c) 2003-2008 Fabrice Bellard + * Copyright (c) 2009-2017 QEMU contributors + * + * 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/osdep.h" +#include "qapi/error.h" +#include "qemu-common.h" +#include "block/aio.h" +#include "block/thread-pool.h" +#include "qemu/main-loop.h" +#include "qemu/atomic.h" +#include "block/raw-aio.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; +}; + +void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque) +{ + QEMUBH *bh; + bh = g_new(QEMUBH, 1); + *bh = (QEMUBH){ + .ctx = ctx, + .cb = cb, + .opaque = opaque, + }; + qemu_lockcnt_lock(&ctx->list_lock); + bh->next = ctx->first_bh; + bh->scheduled = 1; + bh->deleted = 1; + /* Make sure that the members are ready before putting bh into list */ + smp_wmb(); + ctx->first_bh = bh; + qemu_lockcnt_unlock(&ctx->list_lock); + aio_notify(ctx); +} + +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_lockcnt_lock(&ctx->list_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_lockcnt_unlock(&ctx->list_lock); + return bh; +} + +void aio_bh_call(QEMUBH *bh) +{ + bh->cb(bh->opaque); +} + +/* Multiple occurrences of aio_bh_poll cannot be called concurrently */ +int aio_bh_poll(AioContext *ctx) +{ + QEMUBH *bh, **bhp, *next; + int ret; + bool deleted = false; + + qemu_lockcnt_inc(&ctx->list_lock); + + ret = 0; + for (bh = atomic_rcu_read(&ctx->first_bh); bh; bh = next) { + next = atomic_rcu_read(&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 (atomic_xchg(&bh->scheduled, 0)) { + /* Idle BHs don't count as progress */ + if (!bh->idle) { + ret = 1; + } + bh->idle = 0; + aio_bh_call(bh); + } + if (bh->deleted) { + deleted = true; + } + } + + /* remove deleted bhs */ + if (!deleted) { + qemu_lockcnt_dec(&ctx->list_lock); + return ret; + } + + if (qemu_lockcnt_dec_and_lock(&ctx->list_lock)) { + bhp = &ctx->first_bh; + while (*bhp) { + bh = *bhp; + if (bh->deleted && !bh->scheduled) { + *bhp = bh->next; + g_free(bh); + } else { + bhp = &bh->next; + } + } + qemu_lockcnt_unlock(&ctx->list_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 = atomic_rcu_read(&ctx->first_bh); bh; + bh = atomic_rcu_read(&bh->next)) { + if (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->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, true); + return true; +} + +static void +aio_ctx_finalize(GSource *source) +{ + AioContext *ctx = (AioContext *) source; + + thread_pool_free(ctx->thread_pool); + +#ifdef CONFIG_LINUX_AIO + if (ctx->linux_aio) { + laio_detach_aio_context(ctx->linux_aio, ctx); + laio_cleanup(ctx->linux_aio); + ctx->linux_aio = NULL; + } +#endif + + qemu_lockcnt_lock(&ctx->list_lock); + assert(!qemu_lockcnt_count(&ctx->list_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_lockcnt_unlock(&ctx->list_lock); + + aio_set_event_notifier(ctx, &ctx->notifier, false, NULL, NULL); + event_notifier_cleanup(&ctx->notifier); + qemu_rec_mutex_destroy(&ctx->lock); + qemu_lockcnt_destroy(&ctx->list_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; +} + +#ifdef CONFIG_LINUX_AIO +LinuxAioState *aio_get_linux_aio(AioContext *ctx) +{ + if (!ctx->linux_aio) { + ctx->linux_aio = laio_init(); + laio_attach_aio_context(ctx->linux_aio, ctx); + } + return ctx->linux_aio; +} +#endif + +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 event_notifier_dummy_cb(EventNotifier *e) +{ +} + +/* Returns true if aio_notify() was called (e.g. a BH was scheduled) */ +static bool event_notifier_poll(void *opaque) +{ + EventNotifier *e = opaque; + AioContext *ctx = container_of(e, AioContext, notifier); + + return atomic_read(&ctx->notified); +} + +AioContext *aio_context_new(Error **errp) +{ + int ret; + AioContext *ctx; + + ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext)); + aio_context_setup(ctx); + + ret = event_notifier_init(&ctx->notifier, false); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to initialize event notifier"); + goto fail; + } + g_source_set_can_recurse(&ctx->source, true); + qemu_lockcnt_init(&ctx->list_lock); + aio_set_event_notifier(ctx, &ctx->notifier, + false, + (EventNotifierHandler *) + event_notifier_dummy_cb, + event_notifier_poll); +#ifdef CONFIG_LINUX_AIO + ctx->linux_aio = NULL; +#endif + ctx->thread_pool = NULL; + qemu_rec_mutex_init(&ctx->lock); + timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx); + + ctx->poll_ns = 0; + ctx->poll_max_ns = 0; + ctx->poll_grow = 0; + ctx->poll_shrink = 0; + + return ctx; +fail: + g_source_destroy(&ctx->source); + return NULL; +} + +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) +{ + qemu_rec_mutex_lock(&ctx->lock); +} + +void aio_context_release(AioContext *ctx) +{ + qemu_rec_mutex_unlock(&ctx->lock); +} |