qemu

async.c (18968B)

---

 /*
  * 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 "qemu/coroutine-tls.h"
 #include "sysemu/cpu-timers.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);
     /*
      * Workaround for record/replay.
      * vCPU execution should be suspended when new BH is set.
      * This is needed to avoid guest timeouts caused
      * by the long cycles of the execution.
      */
     icount_notify_exit();
 }
 
 /* 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, 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 aio_context_notifier_poll_ready(EventNotifier *e)
 {
     /* Do nothing, we just wanted to kick the event loop */
 }
 
 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,
                            aio_context_notifier_poll_ready);
 #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;
 
     ctx->thread_pool_min = 0;
     ctx->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT;
 
     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);
 }
 
 QEMU_DEFINE_STATIC_CO_TLS(AioContext *, my_aiocontext)
 
 AioContext *qemu_get_current_aio_context(void)
 {
     AioContext *ctx = get_my_aiocontext();
     if (ctx) {
         return ctx;
     }
     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(!get_my_aiocontext());
     set_my_aiocontext(ctx);
 }
 
 void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
                                         int64_t max, Error **errp)
 {
 
     if (min > max || !max || min > INT_MAX || max > INT_MAX) {
         error_setg(errp, "bad thread-pool-min/thread-pool-max values");
         return;
     }
 
     ctx->thread_pool_min = min;
     ctx->thread_pool_max = max;
 
     if (ctx->thread_pool) {
         thread_pool_update_params(ctx->thread_pool, ctx);
     }
 }