/* * QEMU aio implementation * * Copyright IBM Corp., 2008 * Copyright Red Hat Inc., 2012 * * Authors: * Anthony Liguori <aliguori@us.ibm.com> * Paolo Bonzini <pbonzini@redhat.com> * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. * * Contributions after 2012-01-13 are licensed under the terms of the * GNU GPL, version 2 or (at your option) any later version. */ #include "qemu/osdep.h" #include "qemu-common.h" #include "block/block.h" #include "qemu/main-loop.h" #include "qemu/queue.h" #include "qemu/sockets.h" #include "qapi/error.h" #include "qemu/rcu_queue.h" struct AioHandler { EventNotifier *e; IOHandler *io_read; IOHandler *io_write; EventNotifierHandler *io_notify; GPollFD pfd; int deleted; void *opaque; bool is_external; QLIST_ENTRY(AioHandler) node; }; static void aio_remove_fd_handler(AioContext *ctx, AioHandler *node) { /* * If the GSource is in the process of being destroyed then * g_source_remove_poll() causes an assertion failure. Skip * removal in that case, because glib cleans up its state during * destruction anyway. */ if (!g_source_is_destroyed(&ctx->source)) { g_source_remove_poll(&ctx->source, &node->pfd); } /* If aio_poll is in progress, just mark the node as deleted */ if (qemu_lockcnt_count(&ctx->list_lock)) { node->deleted = 1; node->pfd.revents = 0; } else { /* Otherwise, delete it for real. We can't just mark it as * deleted because deleted nodes are only cleaned up after * releasing the list_lock. */ QLIST_REMOVE(node, node); g_free(node); } } void aio_set_fd_handler(AioContext *ctx, int fd, bool is_external, IOHandler *io_read, IOHandler *io_write, AioPollFn *io_poll, IOHandler *io_poll_ready, void *opaque) { /* fd is a SOCKET in our case */ AioHandler *old_node; AioHandler *node = NULL; qemu_lockcnt_lock(&ctx->list_lock); QLIST_FOREACH(old_node, &ctx->aio_handlers, node) { if (old_node->pfd.fd == fd && !old_node->deleted) { break; } } if (io_read || io_write) { HANDLE event; long bitmask = 0; /* Alloc and insert if it's not already there */ node = g_new0(AioHandler, 1); node->pfd.fd = fd; node->pfd.events = 0; if (node->io_read) { node->pfd.events |= G_IO_IN; } if (node->io_write) { node->pfd.events |= G_IO_OUT; } node->e = &ctx->notifier; /* Update handler with latest information */ node->opaque = opaque; node->io_read = io_read; node->io_write = io_write; node->is_external = is_external; if (io_read) { bitmask |= FD_READ | FD_ACCEPT | FD_CLOSE; } if (io_write) { bitmask |= FD_WRITE | FD_CONNECT; } QLIST_INSERT_HEAD_RCU(&ctx->aio_handlers, node, node); event = event_notifier_get_handle(&ctx->notifier); WSAEventSelect(node->pfd.fd, event, bitmask); } if (old_node) { aio_remove_fd_handler(ctx, old_node); } qemu_lockcnt_unlock(&ctx->list_lock); aio_notify(ctx); } void aio_set_fd_poll(AioContext *ctx, int fd, IOHandler *io_poll_begin, IOHandler *io_poll_end) { /* Not implemented */ } void aio_set_event_notifier(AioContext *ctx, EventNotifier *e, bool is_external, EventNotifierHandler *io_notify, AioPollFn *io_poll, EventNotifierHandler *io_poll_ready) { AioHandler *node; qemu_lockcnt_lock(&ctx->list_lock); QLIST_FOREACH(node, &ctx->aio_handlers, node) { if (node->e == e && !node->deleted) { break; } } /* Are we deleting the fd handler? */ if (!io_notify) { if (node) { aio_remove_fd_handler(ctx, node); } } else { if (node == NULL) { /* Alloc and insert if it's not already there */ node = g_new0(AioHandler, 1); node->e = e; node->pfd.fd = (uintptr_t)event_notifier_get_handle(e); node->pfd.events = G_IO_IN; node->is_external = is_external; QLIST_INSERT_HEAD_RCU(&ctx->aio_handlers, node, node); g_source_add_poll(&ctx->source, &node->pfd); } /* Update handler with latest information */ node->io_notify = io_notify; } qemu_lockcnt_unlock(&ctx->list_lock); aio_notify(ctx); } void aio_set_event_notifier_poll(AioContext *ctx, EventNotifier *notifier, EventNotifierHandler *io_poll_begin, EventNotifierHandler *io_poll_end) { /* Not implemented */ } bool aio_prepare(AioContext *ctx) { static struct timeval tv0; AioHandler *node; bool have_select_revents = false; fd_set rfds, wfds; /* * We have to walk very carefully in case aio_set_fd_handler is * called while we're walking. */ qemu_lockcnt_inc(&ctx->list_lock); /* fill fd sets */ FD_ZERO(&rfds); FD_ZERO(&wfds); QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { if (node->io_read) { FD_SET ((SOCKET)node->pfd.fd, &rfds); } if (node->io_write) { FD_SET ((SOCKET)node->pfd.fd, &wfds); } } if (select(0, &rfds, &wfds, NULL, &tv0) > 0) { QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { node->pfd.revents = 0; if (FD_ISSET(node->pfd.fd, &rfds)) { node->pfd.revents |= G_IO_IN; have_select_revents = true; } if (FD_ISSET(node->pfd.fd, &wfds)) { node->pfd.revents |= G_IO_OUT; have_select_revents = true; } } } qemu_lockcnt_dec(&ctx->list_lock); return have_select_revents; } bool aio_pending(AioContext *ctx) { AioHandler *node; bool result = false; /* * We have to walk very carefully in case aio_set_fd_handler is * called while we're walking. */ qemu_lockcnt_inc(&ctx->list_lock); QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { if (node->pfd.revents && node->io_notify) { result = true; break; } if ((node->pfd.revents & G_IO_IN) && node->io_read) { result = true; break; } if ((node->pfd.revents & G_IO_OUT) && node->io_write) { result = true; break; } } qemu_lockcnt_dec(&ctx->list_lock); return result; } static bool aio_dispatch_handlers(AioContext *ctx, HANDLE event) { AioHandler *node; bool progress = false; AioHandler *tmp; /* * We have to walk very carefully in case aio_set_fd_handler is * called while we're walking. */ QLIST_FOREACH_SAFE_RCU(node, &ctx->aio_handlers, node, tmp) { int revents = node->pfd.revents; if (!node->deleted && (revents || event_notifier_get_handle(node->e) == event) && node->io_notify) { node->pfd.revents = 0; node->io_notify(node->e); /* aio_notify() does not count as progress */ if (node->e != &ctx->notifier) { progress = true; } } if (!node->deleted && (node->io_read || node->io_write)) { node->pfd.revents = 0; if ((revents & G_IO_IN) && node->io_read) { node->io_read(node->opaque); progress = true; } if ((revents & G_IO_OUT) && node->io_write) { node->io_write(node->opaque); progress = true; } /* if the next select() will return an event, we have progressed */ if (event == event_notifier_get_handle(&ctx->notifier)) { WSANETWORKEVENTS ev; WSAEnumNetworkEvents(node->pfd.fd, event, &ev); if (ev.lNetworkEvents) { progress = true; } } } if (node->deleted) { if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) { QLIST_REMOVE(node, node); g_free(node); qemu_lockcnt_inc_and_unlock(&ctx->list_lock); } } } return progress; } void aio_dispatch(AioContext *ctx) { qemu_lockcnt_inc(&ctx->list_lock); aio_bh_poll(ctx); aio_dispatch_handlers(ctx, INVALID_HANDLE_VALUE); qemu_lockcnt_dec(&ctx->list_lock); timerlistgroup_run_timers(&ctx->tlg); } bool aio_poll(AioContext *ctx, bool blocking) { AioHandler *node; HANDLE events[MAXIMUM_WAIT_OBJECTS + 1]; bool progress, have_select_revents, first; int count; int timeout; /* * There cannot be two concurrent aio_poll calls for the same AioContext (or * an aio_poll concurrent with a GSource prepare/check/dispatch callback). * We rely on this below to avoid slow locked accesses to ctx->notify_me. * * aio_poll() may only be called in the AioContext's thread. iohandler_ctx * is special in that it runs in the main thread, but that thread's context * is qemu_aio_context. */ assert(in_aio_context_home_thread(ctx == iohandler_get_aio_context() ? qemu_get_aio_context() : ctx)); progress = false; /* aio_notify can avoid the expensive event_notifier_set if * everything (file descriptors, bottom halves, timers) will * be re-evaluated before the next blocking poll(). This is * already true when aio_poll is called with blocking == false; * if blocking == true, it is only true after poll() returns, * so disable the optimization now. */ if (blocking) { qatomic_set(&ctx->notify_me, qatomic_read(&ctx->notify_me) + 2); /* * Write ctx->notify_me before computing the timeout * (reading bottom half flags, etc.). Pairs with * smp_mb in aio_notify(). */ smp_mb(); } qemu_lockcnt_inc(&ctx->list_lock); have_select_revents = aio_prepare(ctx); /* fill fd sets */ count = 0; QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { if (!node->deleted && node->io_notify && aio_node_check(ctx, node->is_external)) { events[count++] = event_notifier_get_handle(node->e); } } first = true; /* ctx->notifier is always registered. */ assert(count > 0); /* Multiple iterations, all of them non-blocking except the first, * may be necessary to process all pending events. After the first * WaitForMultipleObjects call ctx->notify_me will be decremented. */ do { HANDLE event; int ret; timeout = blocking && !have_select_revents ? qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)) : 0; ret = WaitForMultipleObjects(count, events, FALSE, timeout); if (blocking) { assert(first); qatomic_store_release(&ctx->notify_me, qatomic_read(&ctx->notify_me) - 2); aio_notify_accept(ctx); } if (first) { progress |= aio_bh_poll(ctx); first = false; } /* if we have any signaled events, dispatch event */ event = NULL; if ((DWORD) (ret - WAIT_OBJECT_0) < count) { event = events[ret - WAIT_OBJECT_0]; events[ret - WAIT_OBJECT_0] = events[--count]; } else if (!have_select_revents) { break; } have_select_revents = false; blocking = false; progress |= aio_dispatch_handlers(ctx, event); } while (count > 0); qemu_lockcnt_dec(&ctx->list_lock); progress |= timerlistgroup_run_timers(&ctx->tlg); return progress; } void aio_context_setup(AioContext *ctx) { } void aio_context_destroy(AioContext *ctx) { } void aio_context_use_g_source(AioContext *ctx) { } void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, int64_t grow, int64_t shrink, Error **errp) { if (max_ns) { error_setg(errp, "AioContext polling is not implemented on Windows"); } } void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch, Error **errp) { }