diff options
Diffstat (limited to 'util/async.c')
| -rw-r--r-- | util/async.c | 690 |
1 files changed, 690 insertions, 0 deletions
diff --git a/util/async.c b/util/async.c new file mode 100644 index 000000000..6f6717a34 --- /dev/null +++ b/util/async.c @@ -0,0 +1,690 @@ +/* + * 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 "block/aio.h" +#include "block/thread-pool.h" +#include "qemu/main-loop.h" +#include "qemu/atomic.h" +#include "qemu/rcu_queue.h" +#include "block/raw-aio.h" +#include "qemu/coroutine_int.h" +#include "trace.h" + +/***********************************************************/ +/* bottom halves (can be seen as timers which expire ASAP) */ + +/* QEMUBH::flags values */ +enum { + /* Already enqueued and waiting for aio_bh_poll() */ + BH_PENDING = (1 << 0), + + /* Invoke the callback */ + BH_SCHEDULED = (1 << 1), + + /* Delete without invoking callback */ + BH_DELETED = (1 << 2), + + /* Delete after invoking callback */ + BH_ONESHOT = (1 << 3), + + /* Schedule periodically when the event loop is idle */ + BH_IDLE = (1 << 4), +}; + +struct QEMUBH { + AioContext *ctx; + const char *name; + QEMUBHFunc *cb; + void *opaque; + QSLIST_ENTRY(QEMUBH) next; + unsigned flags; +}; + +/* Called concurrently from any thread */ +static void aio_bh_enqueue(QEMUBH *bh, unsigned new_flags) +{ + AioContext *ctx = bh->ctx; + unsigned old_flags; + + /* + * The memory barrier implicit in qatomic_fetch_or 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 the callback has a chance to execute and bh + * could be freed. + */ + old_flags = qatomic_fetch_or(&bh->flags, BH_PENDING | new_flags); + if (!(old_flags & BH_PENDING)) { + QSLIST_INSERT_HEAD_ATOMIC(&ctx->bh_list, bh, next); + } + + aio_notify(ctx); +} + +/* Only called from aio_bh_poll() and aio_ctx_finalize() */ +static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags) +{ + QEMUBH *bh = QSLIST_FIRST_RCU(head); + + if (!bh) { + return NULL; + } + + QSLIST_REMOVE_HEAD(head, next); + + /* + * The qatomic_and is paired with aio_bh_enqueue(). 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 cleared + * flag before bh->cb has run, and thus will call aio_notify again if + * necessary. + */ + *flags = qatomic_fetch_and(&bh->flags, + ~(BH_PENDING | BH_SCHEDULED | BH_IDLE)); + return bh; +} + +void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, + void *opaque, const char *name) +{ + QEMUBH *bh; + bh = g_new(QEMUBH, 1); + *bh = (QEMUBH){ + .ctx = ctx, + .cb = cb, + .opaque = opaque, + .name = name, + }; + aio_bh_enqueue(bh, BH_SCHEDULED | BH_ONESHOT); +} + +QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, + const char *name) +{ + QEMUBH *bh; + bh = g_new(QEMUBH, 1); + *bh = (QEMUBH){ + .ctx = ctx, + .cb = cb, + .opaque = opaque, + .name = name, + }; + 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) +{ + BHListSlice slice; + BHListSlice *s; + int ret = 0; + + QSLIST_MOVE_ATOMIC(&slice.bh_list, &ctx->bh_list); + QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next); + + while ((s = QSIMPLEQ_FIRST(&ctx->bh_slice_list))) { + QEMUBH *bh; + unsigned flags; + + bh = aio_bh_dequeue(&s->bh_list, &flags); + if (!bh) { + QSIMPLEQ_REMOVE_HEAD(&ctx->bh_slice_list, next); + continue; + } + + if ((flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) { + /* Idle BHs don't count as progress */ + if (!(flags & BH_IDLE)) { + ret = 1; + } + aio_bh_call(bh); + } + if (flags & (BH_DELETED | BH_ONESHOT)) { + g_free(bh); + } + } + + return ret; +} + +void qemu_bh_schedule_idle(QEMUBH *bh) +{ + aio_bh_enqueue(bh, BH_SCHEDULED | BH_IDLE); +} + +void qemu_bh_schedule(QEMUBH *bh) +{ + aio_bh_enqueue(bh, BH_SCHEDULED); +} + +/* This func is async. + */ +void qemu_bh_cancel(QEMUBH *bh) +{ + qatomic_and(&bh->flags, ~BH_SCHEDULED); +} + +/* This func is async.The bottom half will do the delete action at the finial + * end. + */ +void qemu_bh_delete(QEMUBH *bh) +{ + aio_bh_enqueue(bh, BH_DELETED); +} + +static int64_t aio_compute_bh_timeout(BHList *head, int timeout) +{ + QEMUBH *bh; + + QSLIST_FOREACH_RCU(bh, head, next) { + if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) { + if (bh->flags & 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; + } + } + } + + return timeout; +} + +int64_t +aio_compute_timeout(AioContext *ctx) +{ + BHListSlice *s; + int64_t deadline; + int timeout = -1; + + timeout = aio_compute_bh_timeout(&ctx->bh_list, timeout); + if (timeout == 0) { + return 0; + } + + QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) { + timeout = aio_compute_bh_timeout(&s->bh_list, timeout); + if (timeout == 0) { + 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; + + qatomic_set(&ctx->notify_me, qatomic_read(&ctx->notify_me) | 1); + + /* + * Write ctx->notify_me before computing the timeout + * (reading bottom half flags, etc.). Pairs with + * smp_mb in aio_notify(). + */ + smp_mb(); + + /* 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; + BHListSlice *s; + + /* Finish computing the timeout before clearing the flag. */ + qatomic_store_release(&ctx->notify_me, qatomic_read(&ctx->notify_me) & ~1); + aio_notify_accept(ctx); + + QSLIST_FOREACH_RCU(bh, &ctx->bh_list, next) { + if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) { + return true; + } + } + + QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) { + QSLIST_FOREACH_RCU(bh, &s->bh_list, next) { + if ((bh->flags & (BH_SCHEDULED | 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; + QEMUBH *bh; + unsigned flags; + + 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 + +#ifdef CONFIG_LINUX_IO_URING + if (ctx->linux_io_uring) { + luring_detach_aio_context(ctx->linux_io_uring, ctx); + luring_cleanup(ctx->linux_io_uring); + ctx->linux_io_uring = NULL; + } +#endif + + assert(QSLIST_EMPTY(&ctx->scheduled_coroutines)); + qemu_bh_delete(ctx->co_schedule_bh); + + /* There must be no aio_bh_poll() calls going on */ + assert(QSIMPLEQ_EMPTY(&ctx->bh_slice_list)); + + while ((bh = aio_bh_dequeue(&ctx->bh_list, &flags))) { + /* + * qemu_bh_delete() must have been called on BHs in this AioContext. In + * many cases memory leaks, hangs, or inconsistent state occur when a + * BH is leaked because something still expects it to run. + * + * If you hit this, fix the lifecycle of the BH so that + * qemu_bh_delete() and any associated cleanup is called before the + * AioContext is finalized. + */ + if (unlikely(!(flags & BH_DELETED))) { + fprintf(stderr, "%s: BH '%s' leaked, aborting...\n", + __func__, bh->name); + abort(); + } + + g_free(bh); + } + + 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); + aio_context_destroy(ctx); +} + +static GSourceFuncs aio_source_funcs = { + aio_ctx_prepare, + aio_ctx_check, + aio_ctx_dispatch, + aio_ctx_finalize +}; + +GSource *aio_get_g_source(AioContext *ctx) +{ + aio_context_use_g_source(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_setup_linux_aio(AioContext *ctx, Error **errp) +{ + if (!ctx->linux_aio) { + ctx->linux_aio = laio_init(errp); + if (ctx->linux_aio) { + laio_attach_aio_context(ctx->linux_aio, ctx); + } + } + return ctx->linux_aio; +} + +LinuxAioState *aio_get_linux_aio(AioContext *ctx) +{ + assert(ctx->linux_aio); + return ctx->linux_aio; +} +#endif + +#ifdef CONFIG_LINUX_IO_URING +LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp) +{ + if (ctx->linux_io_uring) { + return ctx->linux_io_uring; + } + + ctx->linux_io_uring = luring_init(errp); + if (!ctx->linux_io_uring) { + return NULL; + } + + luring_attach_aio_context(ctx->linux_io_uring, ctx); + return ctx->linux_io_uring; +} + +LuringState *aio_get_linux_io_uring(AioContext *ctx) +{ + assert(ctx->linux_io_uring); + return ctx->linux_io_uring; +} +#endif + +void aio_notify(AioContext *ctx) +{ + /* + * Write e.g. bh->flags before writing ctx->notified. Pairs with smp_mb in + * aio_notify_accept. + */ + smp_wmb(); + qatomic_set(&ctx->notified, true); + + /* + * Write ctx->notified before reading ctx->notify_me. Pairs + * with smp_mb in aio_ctx_prepare or aio_poll. + */ + smp_mb(); + if (qatomic_read(&ctx->notify_me)) { + event_notifier_set(&ctx->notifier); + } +} + +void aio_notify_accept(AioContext *ctx) +{ + qatomic_set(&ctx->notified, false); + + /* + * Write ctx->notified before reading e.g. bh->flags. Pairs with smp_wmb + * in aio_notify. + */ + smp_mb(); +} + +static void aio_timerlist_notify(void *opaque, QEMUClockType type) +{ + aio_notify(opaque); +} + +static void aio_context_notifier_cb(EventNotifier *e) +{ + AioContext *ctx = container_of(e, AioContext, notifier); + + event_notifier_test_and_clear(&ctx->notifier); +} + +/* Returns true if aio_notify() was called (e.g. a BH was scheduled) */ +static bool aio_context_notifier_poll(void *opaque) +{ + EventNotifier *e = opaque; + AioContext *ctx = container_of(e, AioContext, notifier); + + return qatomic_read(&ctx->notified); +} + +static void co_schedule_bh_cb(void *opaque) +{ + AioContext *ctx = opaque; + QSLIST_HEAD(, Coroutine) straight, reversed; + + QSLIST_MOVE_ATOMIC(&reversed, &ctx->scheduled_coroutines); + QSLIST_INIT(&straight); + + while (!QSLIST_EMPTY(&reversed)) { + Coroutine *co = QSLIST_FIRST(&reversed); + QSLIST_REMOVE_HEAD(&reversed, co_scheduled_next); + QSLIST_INSERT_HEAD(&straight, co, co_scheduled_next); + } + + while (!QSLIST_EMPTY(&straight)) { + Coroutine *co = QSLIST_FIRST(&straight); + QSLIST_REMOVE_HEAD(&straight, co_scheduled_next); + trace_aio_co_schedule_bh_cb(ctx, co); + aio_context_acquire(ctx); + + /* Protected by write barrier in qemu_aio_coroutine_enter */ + qatomic_set(&co->scheduled, NULL); + qemu_aio_coroutine_enter(ctx, co); + aio_context_release(ctx); + } +} + +AioContext *aio_context_new(Error **errp) +{ + int ret; + AioContext *ctx; + + ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext)); + QSLIST_INIT(&ctx->bh_list); + QSIMPLEQ_INIT(&ctx->bh_slice_list); + 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); + + ctx->co_schedule_bh = aio_bh_new(ctx, co_schedule_bh_cb, ctx); + QSLIST_INIT(&ctx->scheduled_coroutines); + + aio_set_event_notifier(ctx, &ctx->notifier, + false, + aio_context_notifier_cb, + aio_context_notifier_poll); +#ifdef CONFIG_LINUX_AIO + ctx->linux_aio = NULL; +#endif + +#ifdef CONFIG_LINUX_IO_URING + ctx->linux_io_uring = 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; + + ctx->aio_max_batch = 0; + + return ctx; +fail: + g_source_destroy(&ctx->source); + return NULL; +} + +void aio_co_schedule(AioContext *ctx, Coroutine *co) +{ + trace_aio_co_schedule(ctx, co); + const char *scheduled = qatomic_cmpxchg(&co->scheduled, NULL, + __func__); + + if (scheduled) { + fprintf(stderr, + "%s: Co-routine was already scheduled in '%s'\n", + __func__, scheduled); + abort(); + } + + /* The coroutine might run and release the last ctx reference before we + * invoke qemu_bh_schedule(). Take a reference to keep ctx alive until + * we're done. + */ + aio_context_ref(ctx); + + QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines, + co, co_scheduled_next); + qemu_bh_schedule(ctx->co_schedule_bh); + + aio_context_unref(ctx); +} + +typedef struct AioCoRescheduleSelf { + Coroutine *co; + AioContext *new_ctx; +} AioCoRescheduleSelf; + +static void aio_co_reschedule_self_bh(void *opaque) +{ + AioCoRescheduleSelf *data = opaque; + aio_co_schedule(data->new_ctx, data->co); +} + +void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx) +{ + AioContext *old_ctx = qemu_get_current_aio_context(); + + if (old_ctx != new_ctx) { + AioCoRescheduleSelf data = { + .co = qemu_coroutine_self(), + .new_ctx = new_ctx, + }; + /* + * We can't directly schedule the coroutine in the target context + * because this would be racy: The other thread could try to enter the + * coroutine before it has yielded in this one. + */ + aio_bh_schedule_oneshot(old_ctx, aio_co_reschedule_self_bh, &data); + qemu_coroutine_yield(); + } +} + +void aio_co_wake(struct Coroutine *co) +{ + AioContext *ctx; + + /* Read coroutine before co->ctx. Matches smp_wmb in + * qemu_coroutine_enter. + */ + smp_read_barrier_depends(); + ctx = qatomic_read(&co->ctx); + + aio_co_enter(ctx, co); +} + +void aio_co_enter(AioContext *ctx, struct Coroutine *co) +{ + if (ctx != qemu_get_current_aio_context()) { + aio_co_schedule(ctx, co); + return; + } + + if (qemu_in_coroutine()) { + Coroutine *self = qemu_coroutine_self(); + assert(self != co); + QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, co, co_queue_next); + } else { + aio_context_acquire(ctx); + qemu_aio_coroutine_enter(ctx, co); + aio_context_release(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) +{ + qemu_rec_mutex_lock(&ctx->lock); +} + +void aio_context_release(AioContext *ctx) +{ + qemu_rec_mutex_unlock(&ctx->lock); +} + +static __thread AioContext *my_aiocontext; + +AioContext *qemu_get_current_aio_context(void) +{ + if (my_aiocontext) { + return my_aiocontext; + } + if (qemu_mutex_iothread_locked()) { + /* Possibly in a vCPU thread. */ + return qemu_get_aio_context(); + } + return NULL; +} + +void qemu_set_current_aio_context(AioContext *ctx) +{ + assert(!my_aiocontext); + my_aiocontext = ctx; +} |