From patchwork Tue Jan 5 13:09:30 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 11998855 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1AFFC433E0 for ; Tue, 5 Jan 2021 13:09:41 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 88D6522240 for ; Tue, 5 Jan 2021 13:09:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 88D6522240 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.61921.109229 (Exim 4.92) (envelope-from ) id 1kwm5d-00081d-VC; Tue, 05 Jan 2021 13:09:33 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 61921.109229; Tue, 05 Jan 2021 13:09:33 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kwm5d-00081W-Rp; Tue, 05 Jan 2021 13:09:33 +0000 Received: by outflank-mailman (input) for mailman id 61921; Tue, 05 Jan 2021 13:09:33 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kwm5c-00081Q-WD for xen-devel@lists.xenproject.org; Tue, 05 Jan 2021 13:09:33 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 87474077-90a6-4260-b7b1-ab1383ecc613; Tue, 05 Jan 2021 13:09:32 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 523B4AD19; Tue, 5 Jan 2021 13:09:31 +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: 87474077-90a6-4260-b7b1-ab1383ecc613 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1609852171; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UZmBD7Vu9gEKBGq3iumpz+92oYKBoj1HFDeHDpU2UJo=; b=GUGoDOkt4j3ZuksV4UmryzD+IkUOkuoq9fji3WggObuHNt/A0IIsvRakI539Ybe3ajc4X0 JMeLm0rlzdml50docBklx66dhAvonxZCMLjv7iLt5HkYiUvDoMB0ZaXl+G26dXsJM90TJ0 1J3F9MnrP0c8UxszJg3Ln0mGFeq5LzU= Subject: [PATCH v4 02/10] evtchn: bind-interdomain doesn't need to hold both domains' event locks From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Wei Liu , Stefano Stabellini References: Message-ID: <8b21ff13-d6ea-3fa5-8d87-c05157112e4b@suse.com> Date: Tue, 5 Jan 2021 14:09:30 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US The local domain's lock is needed for the port allocation, but for the remote side the per-channel lock is sufficient. The per-channel locks then need to be acquired slightly earlier, though. Signed-off-by: Jan Beulich --- v4: New. --- a/xen/common/event_channel.c +++ b/xen/common/event_channel.c @@ -355,18 +355,7 @@ static long evtchn_bind_interdomain(evtc if ( (rd = rcu_lock_domain_by_id(rdom)) == NULL ) return -ESRCH; - /* Avoid deadlock by first acquiring lock of domain with smaller id. */ - if ( ld < rd ) - { - spin_lock(&ld->event_lock); - spin_lock(&rd->event_lock); - } - else - { - if ( ld != rd ) - spin_lock(&rd->event_lock); - spin_lock(&ld->event_lock); - } + spin_lock(&ld->event_lock); if ( (lport = get_free_port(ld)) < 0 ) ERROR_EXIT(lport); @@ -375,15 +364,19 @@ static long evtchn_bind_interdomain(evtc if ( !port_is_valid(rd, rport) ) ERROR_EXIT_DOM(-EINVAL, rd); rchn = evtchn_from_port(rd, rport); + + double_evtchn_lock(lchn, rchn); + if ( (rchn->state != ECS_UNBOUND) || (rchn->u.unbound.remote_domid != ld->domain_id) ) ERROR_EXIT_DOM(-EINVAL, rd); rc = xsm_evtchn_interdomain(XSM_HOOK, ld, lchn, rd, rchn); if ( rc ) + { + double_evtchn_unlock(lchn, rchn); goto out; - - double_evtchn_lock(lchn, rchn); + } lchn->u.interdomain.remote_dom = rd; lchn->u.interdomain.remote_port = rport; @@ -407,8 +400,6 @@ static long evtchn_bind_interdomain(evtc out: check_free_port(ld, lport); spin_unlock(&ld->event_lock); - if ( ld != rd ) - spin_unlock(&rd->event_lock); rcu_unlock_domain(rd);