From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33958) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cOsev-0004Pm-6n for qemu-devel@nongnu.org; Wed, 04 Jan 2017 15:59:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cOses-0000g7-5d for qemu-devel@nongnu.org; Wed, 04 Jan 2017 15:59:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38550) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cOser-0000fA-Vk for qemu-devel@nongnu.org; Wed, 04 Jan 2017 15:59:42 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1332F37F1F for ; Wed, 4 Jan 2017 20:59:42 +0000 (UTC) From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Wed, 4 Jan 2017 21:59:36 +0100 Message-Id: <20170104205936.27279-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH] win32: fix main-loop busy loop on socket/fd event List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: pbonzini@redhat.com, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Commit 05e514b1d4d5bd4209e2c8bbc76ff05c85a235f3 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 commit d3385eb448e38f828c78f8f68ec5d79c66a58b5d). 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()). Signed-off-by: Marc-Andr=C3=A9 Lureau --- include/block/aio.h | 2 ++ async.c | 6 ++++++ 2 files changed, 8 insertions(+) diff --git a/include/block/aio.h b/include/block/aio.h index ca551e346f..a6da135bf3 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -100,6 +100,7 @@ struct AioContext { */ int walking_bh; =20 +#ifndef _WIN32 /* Used by aio_notify. * * "notified" is used to avoid expensive event_notifier_test_and_cle= ar @@ -113,6 +114,7 @@ struct AioContext { * in the docs/aio_notify_accept.promela formal model. */ bool notified; +#endif EventNotifier notifier; =20 /* Thread pool for performing work and receiving completion callback= s */ diff --git a/async.c b/async.c index b2de360c23..8c2a68b6cc 100644 --- a/async.c +++ b/async.c @@ -329,15 +329,21 @@ void aio_notify(AioContext *ctx) smp_mb(); if (ctx->notify_me) { event_notifier_set(&ctx->notifier); +#ifndef _WIN32 atomic_mb_set(&ctx->notified, true); +#endif } } =20 void aio_notify_accept(AioContext *ctx) { +#ifndef _WIN32 if (atomic_xchg(&ctx->notified, false)) { +#endif event_notifier_test_and_clear(&ctx->notifier); +#ifndef _WIN32 } +#endif } =20 static void aio_timerlist_notify(void *opaque) --=20 2.11.0