From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1086BC46CCD for ; Tue, 19 Dec 2023 15:28:51 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.656989.1025550 (Exim 4.92) (envelope-from ) id 1rFc1S-00068s-Bm; Tue, 19 Dec 2023 15:28:42 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 656989.1025550; Tue, 19 Dec 2023 15:28:42 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rFc1S-00068l-93; Tue, 19 Dec 2023 15:28:42 +0000 Received: by outflank-mailman (input) for mailman id 656989; Tue, 19 Dec 2023 15:28:41 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rFc1R-00068d-8L for xen-devel@lists.xenproject.org; Tue, 19 Dec 2023 15:28:41 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 48924455-9e83-11ee-98eb-6d05b1d4d9a1; Tue, 19 Dec 2023 16:28:40 +0100 (CET) Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-74-6mtZLgXrPG-ASdwrw9encw-1; Tue, 19 Dec 2023 10:28:32 -0500 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 05769383A0A1; Tue, 19 Dec 2023 15:28:31 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.175]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3201F492BC6; Tue, 19 Dec 2023 15:28:26 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 48924455-9e83-11ee-98eb-6d05b1d4d9a1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1702999718; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Nh0cR65sPswywtceyI2IIIl2ItyyUhcWzRQaZepOBXU=; b=CcA56sIoWzeFL528blg5CscoaV0BtqfxWMt/0ijrtICsQfpmkYPjyW1/H3/y6w0NVOwARM B5Ne7b9KCfCIMOTQu6hbrlmllU3IO5FyT20rN0USzkEdmYHS82yRZGZlR6VBhiz6dMrlUj VlxCtXtadM6tDqZ7pLk8G05XaVjh/GY= X-MC-Unique: 6mtZLgXrPG-ASdwrw9encw-1 Date: Tue, 19 Dec 2023 16:28:25 +0100 From: Kevin Wolf To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Vladimir Sementsov-Ogievskiy , Cleber Rosa , Xie Changlong , Paul Durrant , Ari Sundholm , Jason Wang , Eric Blake , John Snow , Eduardo Habkost , Wen Congyang , Alberto Garcia , Anthony Perard , "Michael S. Tsirkin" , Stefano Stabellini , qemu-block@nongnu.org, Juan Quintela , Paolo Bonzini , Coiby Xu , Fabiano Rosas , Hanna Reitz , Zhang Chen , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Pavel Dovgalyuk , Peter Xu , Emanuele Giuseppe Esposito , Fam Zheng , Leonardo Bras , David Hildenbrand , Li Zhijian , xen-devel@lists.xenproject.org Subject: Re: [PATCH v2 04/14] aio: make aio_context_acquire()/aio_context_release() a no-op Message-ID: References: <20231205182011.1976568-1-stefanha@redhat.com> <20231205182011.1976568-5-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231205182011.1976568-5-stefanha@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 Am 05.12.2023 um 19:20 hat Stefan Hajnoczi geschrieben: > aio_context_acquire()/aio_context_release() has been replaced by > fine-grained locking to protect state shared by multiple threads. The > AioContext lock still plays the role of balancing locking in > AIO_WAIT_WHILE() and many functions in QEMU either require that the > AioContext lock is held or not held for this reason. In other words, the > AioContext lock is purely there for consistency with itself and serves > no real purpose anymore. > > Stop actually acquiring/releasing the lock in > aio_context_acquire()/aio_context_release() so that subsequent patches > can remove callers across the codebase incrementally. > > I have performed "make check" and qemu-iotests stress tests across > x86-64, ppc64le, and aarch64 to confirm that there are no failures as a > result of eliminating the lock. > > Signed-off-by: Stefan Hajnoczi > Reviewed-by: Eric Blake > Acked-by: Kevin Wolf I knew why I wasn't confident enough to give a R-b... This crashes qemu-storage-daemon in the qemu-iotests case graph-changes-while-io. qemu-storage-daemon: ../nbd/server.c:2542: nbd_co_receive_request: Assertion `client->recv_coroutine == qemu_coroutine_self()' failed. (gdb) bt #0 0x00007fdb00529884 in __pthread_kill_implementation () from /lib64/libc.so.6 #1 0x00007fdb004d8afe in raise () from /lib64/libc.so.6 #2 0x00007fdb004c187f in abort () from /lib64/libc.so.6 #3 0x00007fdb004c179b in __assert_fail_base.cold () from /lib64/libc.so.6 #4 0x00007fdb004d1187 in __assert_fail () from /lib64/libc.so.6 #5 0x0000557f9f9534eb in nbd_co_receive_request (errp=0x7fdafc25eec0, request=0x7fdafc25ef10, req=0x7fdaf00159c0) at ../nbd/server.c:2542 #6 nbd_trip (opaque=0x557fa0b33fa0) at ../nbd/server.c:2962 #7 0x0000557f9faa416b in coroutine_trampoline (i0=, i1=) at ../util/coroutine-ucontext.c:177 #8 0x00007fdb004efe90 in ?? () from /lib64/libc.so.6 #9 0x00007fdafc35f680 in ?? () #10 0x0000000000000000 in ?? () (gdb) p *client $2 = {refcount = 4, close_fn = 0x557f9f95dc40 , exp = 0x557fa0b30590, tlscreds = 0x0, tlsauthz = 0x0, sioc = 0x557fa0b33d90, ioc = 0x557fa0b33d90, recv_coroutine = 0x7fdaf0015eb0, send_lock = {locked = 0, ctx = 0x0, from_push = {slh_first = 0x0}, to_pop = {slh_first = 0x0}, handoff = 0, sequence = 0, holder = 0x0}, send_coroutine = 0x0, read_yielding = false, quiescing = false, next = {tqe_next = 0x0, tqe_circ = {tql_next = 0x0, tql_prev = 0x557fa0b305e8}}, nb_requests = 1, closing = false, check_align = 1, mode = NBD_MODE_EXTENDED, contexts = {exp = 0x557fa0b30590, count = 1, base_allocation = true, allocation_depth = false, bitmaps = 0x0}, opt = 7, optlen = 0} (gdb) p co_tls_current $3 = (Coroutine *) 0x7fdaf00061d0 Kevin