From nobody Tue Nov 26 16:43:33 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1707154076; cv=none; d=zohomail.com; s=zohoarc; b=lEPqJfSUzuMiLKur2TyW3umxxOgnm9inIb0CPQg57aIAEKtdQI4hCipgzt5DxhX/XfTKVpHuBO5r/CfoHCFdJY0Dwsut/1iUQWn8G0b6RHXanZPhBjgFlgcx4OnWyM79PLBm4yiRs05jcxUdAIXZ1tc0gCMbwAllSnQIWGQYHLI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1707154076; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=MoN0Ki9v/7+vDB+dfSjCp/PaiJqIVFi6SHTUNYHmlaI=; b=OjQcH2Jy+d7qF2VoedpMCQR7+/zhtwQJCuWZHuoJ2z1VznIs0pFeNlmnz+ELsYB18Nnod35+ZkctiWGIACBp0V9dcyzp/3dOhhx/AaOoD2JTC4Y1n7jQ+nlp8fUzjzhYHDKeUI7MJ9/ggWBiQ/FW6pejnRXgriYCNJB9Gzk3jD4= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1707154076241137.06775874966695; Mon, 5 Feb 2024 09:27:56 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rX2kc-0008W8-31; Mon, 05 Feb 2024 12:27:22 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rX2kb-0008Vg-2Q for qemu-devel@nongnu.org; Mon, 05 Feb 2024 12:27:21 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rX2kZ-0006Pv-OW for qemu-devel@nongnu.org; Mon, 05 Feb 2024 12:27:20 -0500 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-441-eawk-JpHON6cgFnjiaL3nQ-1; Mon, 05 Feb 2024 12:27:13 -0500 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (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 85B4510B7261; Mon, 5 Feb 2024 17:27:13 +0000 (UTC) Received: from localhost (unknown [10.39.192.69]) by smtp.corp.redhat.com (Postfix) with ESMTP id DFC06492BFA; Mon, 5 Feb 2024 17:27:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707154039; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MoN0Ki9v/7+vDB+dfSjCp/PaiJqIVFi6SHTUNYHmlaI=; b=b92UeApq5T5bOaJNA7SPZeQbi78UhE89MCzP8iUrreik9nH9nt+0Pxho/pr/UE++fV6RYy Kj0AZHW11dzBUuSvZBZrFpkxxsDlw+936hf5cTGN5l6r0hXKCYYM7Hgofv9FrAKO0vCH/p svZamQoq/rdKjmkseTEGh/hYjJVLUWw= X-MC-Unique: eawk-JpHON6cgFnjiaL3nQ-1 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Kevin Wolf , Hanna Reitz , "Michael S. Tsirkin" , Michael Roth , Markus Armbruster , Stefan Hajnoczi , qemu-block@nongnu.org Subject: [PATCH 5/5] monitor: use aio_co_reschedule_self() Date: Mon, 5 Feb 2024 12:26:59 -0500 Message-ID: <20240205172659.476970-6-stefanha@redhat.com> In-Reply-To: <20240205172659.476970-1-stefanha@redhat.com> References: <20240205172659.476970-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.285, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1707154078341100005 Content-Type: text/plain; charset="utf-8" The aio_co_reschedule_self() API is designed to avoid the race condition between scheduling the coroutine in another AioContext and yielding. The QMP dispatch code uses the open-coded version that appears susceptible to the race condition at first glance: aio_co_schedule(qemu_get_aio_context(), qemu_coroutine_self()); qemu_coroutine_yield(); The code is actually safe because the iohandler and qemu_aio_context AioContext run under the Big QEMU Lock. Nevertheless, set a good example and use aio_co_reschedule_self() so it's obvious that there is no race. Suggested-by: Hanna Reitz Signed-off-by: Stefan Hajnoczi Acked-by: Markus Armbruster Reviewed-by: Hanna Czenczek Reviewed-by: Manos Pitsidianakis --- qapi/qmp-dispatch.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c index 176b549473..f3488afeef 100644 --- a/qapi/qmp-dispatch.c +++ b/qapi/qmp-dispatch.c @@ -212,8 +212,7 @@ QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommand= List *cmds, QObject *requ * executing the command handler so that it can make progress = if it * involves an AIO_WAIT_WHILE(). */ - aio_co_schedule(qemu_get_aio_context(), qemu_coroutine_self()); - qemu_coroutine_yield(); + aio_co_reschedule_self(qemu_get_aio_context()); } =20 monitor_set_cur(qemu_coroutine_self(), cur_mon); @@ -227,9 +226,7 @@ QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommand= List *cmds, QObject *requ * Move back to iohandler_ctx so that nested event loops for * qemu_aio_context don't start new monitor commands. */ - aio_co_schedule(iohandler_get_aio_context(), - qemu_coroutine_self()); - qemu_coroutine_yield(); + aio_co_reschedule_self(iohandler_get_aio_context()); } } else { /* --=20 2.43.0