Commit05e514b1d4
introduced an AIO context optimization to avoid calling event_notifier_test_and_clear() on ctx->notifier. On Windows, the same notifier is being used to wakeup the wait on socket events (see commitd3385eb448
). The ctx->notifier event is added to the gpoll sources in aio_set_event_notifier(), aio_ctx_check() should clear the event regardless of ctx->notified, since Windows sets the event by itself, bypassing the aio->notified. This fixes qemu not clearing the event resulting in a busy loop. Paolo suggested to me on irc to call event_notifier_test_and_clear() after select() >0 from aio-win32.c's aio_prepare. Unfortunately, not all fds associated with ctx->notifiers are in AIO fd handlers set. (qemu_set_nonblock() in util/oslib-win32.c calls qemu_fd_register()). This is essentially a v2 of a patch that was sent earlier: https://lists.gnu.org/archive/html/qemu-devel/2017-01/msg00420.html that resurfaced when James investigated Spice performance issues on Windows: https://gitlab.freedesktop.org/spice/spice/issues/36 In order to test that patch, I simply tried running test-char on win32, and it hangs. Applying that patch solves it. QIO idle sources are not dispatched. I haven't investigated much further, I suspect source priorities and busy looping still come into play. This version keeps the "notified" field, so event_notifier_poll() should still work as expected. Cc: James Le Cuirot <chewi@gentoo.org> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
529 lines
13 KiB
C
529 lines
13 KiB
C
/*
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* Data plane event loop
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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* Copyright (c) 2009-2017 QEMU contributors
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu/osdep.h"
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#include "qapi/error.h"
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#include "block/aio.h"
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#include "block/thread-pool.h"
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#include "qemu/main-loop.h"
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#include "qemu/atomic.h"
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#include "block/raw-aio.h"
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#include "qemu/coroutine_int.h"
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#include "trace.h"
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/***********************************************************/
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/* bottom halves (can be seen as timers which expire ASAP) */
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struct QEMUBH {
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AioContext *ctx;
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QEMUBHFunc *cb;
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void *opaque;
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QEMUBH *next;
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bool scheduled;
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bool idle;
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bool deleted;
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};
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void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
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{
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QEMUBH *bh;
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bh = g_new(QEMUBH, 1);
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*bh = (QEMUBH){
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.ctx = ctx,
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.cb = cb,
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.opaque = opaque,
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};
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qemu_lockcnt_lock(&ctx->list_lock);
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bh->next = ctx->first_bh;
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bh->scheduled = 1;
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bh->deleted = 1;
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/* Make sure that the members are ready before putting bh into list */
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smp_wmb();
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ctx->first_bh = bh;
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qemu_lockcnt_unlock(&ctx->list_lock);
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aio_notify(ctx);
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}
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QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
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{
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QEMUBH *bh;
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bh = g_new(QEMUBH, 1);
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*bh = (QEMUBH){
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.ctx = ctx,
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.cb = cb,
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.opaque = opaque,
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};
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qemu_lockcnt_lock(&ctx->list_lock);
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bh->next = ctx->first_bh;
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/* Make sure that the members are ready before putting bh into list */
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smp_wmb();
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ctx->first_bh = bh;
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qemu_lockcnt_unlock(&ctx->list_lock);
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return bh;
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}
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void aio_bh_call(QEMUBH *bh)
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{
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bh->cb(bh->opaque);
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}
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/* Multiple occurrences of aio_bh_poll cannot be called concurrently.
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* The count in ctx->list_lock is incremented before the call, and is
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* not affected by the call.
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*/
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int aio_bh_poll(AioContext *ctx)
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{
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QEMUBH *bh, **bhp, *next;
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int ret;
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bool deleted = false;
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ret = 0;
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for (bh = atomic_rcu_read(&ctx->first_bh); bh; bh = next) {
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next = atomic_rcu_read(&bh->next);
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/* The atomic_xchg is paired with the one in qemu_bh_schedule. The
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* implicit memory barrier ensures that the callback sees all writes
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* done by the scheduling thread. It also ensures that the scheduling
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* thread sees the zero before bh->cb has run, and thus will call
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* aio_notify again if necessary.
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*/
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if (atomic_xchg(&bh->scheduled, 0)) {
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/* Idle BHs don't count as progress */
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if (!bh->idle) {
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ret = 1;
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}
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bh->idle = 0;
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aio_bh_call(bh);
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}
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if (bh->deleted) {
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deleted = true;
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}
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}
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/* remove deleted bhs */
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if (!deleted) {
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return ret;
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}
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if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
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bhp = &ctx->first_bh;
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while (*bhp) {
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bh = *bhp;
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if (bh->deleted && !bh->scheduled) {
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*bhp = bh->next;
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g_free(bh);
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} else {
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bhp = &bh->next;
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}
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}
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qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
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}
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return ret;
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}
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void qemu_bh_schedule_idle(QEMUBH *bh)
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{
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bh->idle = 1;
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/* Make sure that idle & any writes needed by the callback are done
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* before the locations are read in the aio_bh_poll.
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*/
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atomic_mb_set(&bh->scheduled, 1);
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}
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void qemu_bh_schedule(QEMUBH *bh)
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{
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AioContext *ctx;
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ctx = bh->ctx;
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bh->idle = 0;
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/* The memory barrier implicit in atomic_xchg makes sure that:
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* 1. idle & any writes needed by the callback are done before the
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* locations are read in the aio_bh_poll.
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* 2. ctx is loaded before scheduled is set and the callback has a chance
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* to execute.
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*/
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if (atomic_xchg(&bh->scheduled, 1) == 0) {
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aio_notify(ctx);
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}
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}
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/* This func is async.
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*/
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void qemu_bh_cancel(QEMUBH *bh)
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{
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atomic_mb_set(&bh->scheduled, 0);
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}
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/* This func is async.The bottom half will do the delete action at the finial
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* end.
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*/
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void qemu_bh_delete(QEMUBH *bh)
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{
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bh->scheduled = 0;
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bh->deleted = 1;
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}
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int64_t
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aio_compute_timeout(AioContext *ctx)
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{
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int64_t deadline;
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int timeout = -1;
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QEMUBH *bh;
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for (bh = atomic_rcu_read(&ctx->first_bh); bh;
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bh = atomic_rcu_read(&bh->next)) {
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if (bh->scheduled) {
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if (bh->idle) {
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/* idle bottom halves will be polled at least
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* every 10ms */
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timeout = 10000000;
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} else {
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/* non-idle bottom halves will be executed
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* immediately */
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return 0;
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}
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}
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}
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deadline = timerlistgroup_deadline_ns(&ctx->tlg);
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if (deadline == 0) {
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return 0;
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} else {
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return qemu_soonest_timeout(timeout, deadline);
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}
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}
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static gboolean
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aio_ctx_prepare(GSource *source, gint *timeout)
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{
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AioContext *ctx = (AioContext *) source;
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atomic_or(&ctx->notify_me, 1);
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/* We assume there is no timeout already supplied */
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*timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
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if (aio_prepare(ctx)) {
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*timeout = 0;
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}
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return *timeout == 0;
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}
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static gboolean
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aio_ctx_check(GSource *source)
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{
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AioContext *ctx = (AioContext *) source;
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QEMUBH *bh;
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atomic_and(&ctx->notify_me, ~1);
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aio_notify_accept(ctx);
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for (bh = ctx->first_bh; bh; bh = bh->next) {
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if (bh->scheduled) {
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return true;
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}
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}
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return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
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}
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static gboolean
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aio_ctx_dispatch(GSource *source,
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GSourceFunc callback,
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gpointer user_data)
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{
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AioContext *ctx = (AioContext *) source;
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assert(callback == NULL);
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aio_dispatch(ctx);
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return true;
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}
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static void
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aio_ctx_finalize(GSource *source)
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{
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AioContext *ctx = (AioContext *) source;
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thread_pool_free(ctx->thread_pool);
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#ifdef CONFIG_LINUX_AIO
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if (ctx->linux_aio) {
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laio_detach_aio_context(ctx->linux_aio, ctx);
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laio_cleanup(ctx->linux_aio);
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ctx->linux_aio = NULL;
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}
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#endif
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assert(QSLIST_EMPTY(&ctx->scheduled_coroutines));
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qemu_bh_delete(ctx->co_schedule_bh);
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qemu_lockcnt_lock(&ctx->list_lock);
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assert(!qemu_lockcnt_count(&ctx->list_lock));
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while (ctx->first_bh) {
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QEMUBH *next = ctx->first_bh->next;
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/* qemu_bh_delete() must have been called on BHs in this AioContext */
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assert(ctx->first_bh->deleted);
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g_free(ctx->first_bh);
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ctx->first_bh = next;
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}
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qemu_lockcnt_unlock(&ctx->list_lock);
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aio_set_event_notifier(ctx, &ctx->notifier, false, NULL, NULL);
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event_notifier_cleanup(&ctx->notifier);
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qemu_rec_mutex_destroy(&ctx->lock);
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qemu_lockcnt_destroy(&ctx->list_lock);
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timerlistgroup_deinit(&ctx->tlg);
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aio_context_destroy(ctx);
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}
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static GSourceFuncs aio_source_funcs = {
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aio_ctx_prepare,
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aio_ctx_check,
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aio_ctx_dispatch,
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aio_ctx_finalize
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};
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GSource *aio_get_g_source(AioContext *ctx)
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{
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g_source_ref(&ctx->source);
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return &ctx->source;
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}
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ThreadPool *aio_get_thread_pool(AioContext *ctx)
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{
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if (!ctx->thread_pool) {
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ctx->thread_pool = thread_pool_new(ctx);
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}
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return ctx->thread_pool;
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}
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#ifdef CONFIG_LINUX_AIO
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LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp)
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{
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if (!ctx->linux_aio) {
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ctx->linux_aio = laio_init(errp);
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if (ctx->linux_aio) {
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laio_attach_aio_context(ctx->linux_aio, ctx);
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}
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}
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return ctx->linux_aio;
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}
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LinuxAioState *aio_get_linux_aio(AioContext *ctx)
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{
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assert(ctx->linux_aio);
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return ctx->linux_aio;
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}
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#endif
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void aio_notify(AioContext *ctx)
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{
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/* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs
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* with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
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*/
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smp_mb();
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if (ctx->notify_me) {
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event_notifier_set(&ctx->notifier);
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atomic_mb_set(&ctx->notified, true);
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}
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}
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void aio_notify_accept(AioContext *ctx)
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{
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if (atomic_xchg(&ctx->notified, false)
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#ifdef WIN32
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|| true
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#endif
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) {
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event_notifier_test_and_clear(&ctx->notifier);
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}
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}
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static void aio_timerlist_notify(void *opaque, QEMUClockType type)
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{
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aio_notify(opaque);
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}
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static void event_notifier_dummy_cb(EventNotifier *e)
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{
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}
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/* Returns true if aio_notify() was called (e.g. a BH was scheduled) */
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static bool event_notifier_poll(void *opaque)
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{
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EventNotifier *e = opaque;
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AioContext *ctx = container_of(e, AioContext, notifier);
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return atomic_read(&ctx->notified);
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}
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static void co_schedule_bh_cb(void *opaque)
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{
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AioContext *ctx = opaque;
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QSLIST_HEAD(, Coroutine) straight, reversed;
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QSLIST_MOVE_ATOMIC(&reversed, &ctx->scheduled_coroutines);
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QSLIST_INIT(&straight);
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while (!QSLIST_EMPTY(&reversed)) {
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Coroutine *co = QSLIST_FIRST(&reversed);
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QSLIST_REMOVE_HEAD(&reversed, co_scheduled_next);
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QSLIST_INSERT_HEAD(&straight, co, co_scheduled_next);
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}
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while (!QSLIST_EMPTY(&straight)) {
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Coroutine *co = QSLIST_FIRST(&straight);
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QSLIST_REMOVE_HEAD(&straight, co_scheduled_next);
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trace_aio_co_schedule_bh_cb(ctx, co);
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aio_context_acquire(ctx);
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/* Protected by write barrier in qemu_aio_coroutine_enter */
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atomic_set(&co->scheduled, NULL);
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qemu_aio_coroutine_enter(ctx, co);
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aio_context_release(ctx);
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}
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}
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AioContext *aio_context_new(Error **errp)
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{
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int ret;
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AioContext *ctx;
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ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
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aio_context_setup(ctx);
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ret = event_notifier_init(&ctx->notifier, false);
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if (ret < 0) {
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error_setg_errno(errp, -ret, "Failed to initialize event notifier");
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goto fail;
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}
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g_source_set_can_recurse(&ctx->source, true);
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qemu_lockcnt_init(&ctx->list_lock);
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ctx->co_schedule_bh = aio_bh_new(ctx, co_schedule_bh_cb, ctx);
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QSLIST_INIT(&ctx->scheduled_coroutines);
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aio_set_event_notifier(ctx, &ctx->notifier,
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false,
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(EventNotifierHandler *)
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event_notifier_dummy_cb,
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event_notifier_poll);
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#ifdef CONFIG_LINUX_AIO
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ctx->linux_aio = NULL;
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#endif
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ctx->thread_pool = NULL;
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qemu_rec_mutex_init(&ctx->lock);
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timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
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ctx->poll_ns = 0;
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ctx->poll_max_ns = 0;
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ctx->poll_grow = 0;
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ctx->poll_shrink = 0;
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return ctx;
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fail:
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g_source_destroy(&ctx->source);
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return NULL;
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}
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void aio_co_schedule(AioContext *ctx, Coroutine *co)
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{
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trace_aio_co_schedule(ctx, co);
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const char *scheduled = atomic_cmpxchg(&co->scheduled, NULL,
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__func__);
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if (scheduled) {
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fprintf(stderr,
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"%s: Co-routine was already scheduled in '%s'\n",
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__func__, scheduled);
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abort();
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}
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/* The coroutine might run and release the last ctx reference before we
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* invoke qemu_bh_schedule(). Take a reference to keep ctx alive until
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* we're done.
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*/
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aio_context_ref(ctx);
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QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
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co, co_scheduled_next);
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qemu_bh_schedule(ctx->co_schedule_bh);
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aio_context_unref(ctx);
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}
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void aio_co_wake(struct Coroutine *co)
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{
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AioContext *ctx;
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/* Read coroutine before co->ctx. Matches smp_wmb in
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* qemu_coroutine_enter.
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*/
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smp_read_barrier_depends();
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ctx = atomic_read(&co->ctx);
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aio_co_enter(ctx, co);
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}
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void aio_co_enter(AioContext *ctx, struct Coroutine *co)
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{
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if (ctx != qemu_get_current_aio_context()) {
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aio_co_schedule(ctx, co);
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return;
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}
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if (qemu_in_coroutine()) {
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Coroutine *self = qemu_coroutine_self();
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assert(self != co);
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QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, co, co_queue_next);
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} else {
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aio_context_acquire(ctx);
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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);
|
|
}
|