From patchwork Tue Jan 5 13:10:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 11998859 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 EFC1AC433DB for ; Tue, 5 Jan 2021 13:10:41 +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 A4F6322240 for ; Tue, 5 Jan 2021 13:10:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A4F6322240 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.61928.109254 (Exim 4.92) (envelope-from ) id 1kwm6b-0000UV-OG; Tue, 05 Jan 2021 13:10:33 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 61928.109254; Tue, 05 Jan 2021 13:10:33 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kwm6b-0000UO-Jb; Tue, 05 Jan 2021 13:10:33 +0000 Received: by outflank-mailman (input) for mailman id 61928; Tue, 05 Jan 2021 13:10:31 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kwm6Z-0000U1-Qe for xen-devel@lists.xenproject.org; Tue, 05 Jan 2021 13:10:31 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 3209bdae-e740-48d3-b719-00c39f9615a1; Tue, 05 Jan 2021 13:10:31 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4F225AD0B; Tue, 5 Jan 2021 13:10:30 +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: 3209bdae-e740-48d3-b719-00c39f9615a1 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=1609852230; 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=7KEt2eAO57gYDz6fS7ggu7fXlsDVJkSylqA5Z3JwCgE=; b=FFUJ5TkCbnI0z71f1760x4zuhufDBpcOZnCjYbLmr5BmYIvYAFXysYJ4yGdwie1lDHAH0K QxEn69BaYE3d38JypCFBDR0bfxL2iY8lVV1XEXlrK+5CtIjfKh22Eq9r8Ub0cEfMf63r4X xeKxzqrJtL3wQRV8XcxDCN6MFSew4fY= Subject: [PATCH v4 04/10] evtchn: don't call Xen consumer callback with per-channel lock held 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: Date: Tue, 5 Jan 2021 14:10:29 +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 While there don't look to be any problems with this right now, the lock order implications from holding the lock can be very difficult to follow (and may be easy to violate unknowingly). The present callbacks don't (and no such callback should) have any need for the lock to be held. Signed-off-by: Jan Beulich Acked-by: Julien Grall --- v4: Go back to v2. v3: Drain callbacks before proceeding with closing. Re-base. --- a/xen/common/event_channel.c +++ b/xen/common/event_channel.c @@ -767,9 +767,18 @@ int evtchn_send(struct domain *ld, unsig rport = lchn->u.interdomain.remote_port; rchn = evtchn_from_port(rd, rport); if ( consumer_is_xen(rchn) ) - xen_notification_fn(rchn)(rd->vcpu[rchn->notify_vcpu_id], rport); - else - evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn); + { + /* Don't keep holding the lock for the call below. */ + xen_event_channel_notification_t fn = xen_notification_fn(rchn); + struct vcpu *rv = rd->vcpu[rchn->notify_vcpu_id]; + + rcu_lock_domain(rd); + evtchn_read_unlock(lchn); + fn(rv, rport); + rcu_unlock_domain(rd); + return 0; + } + evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn); break; case ECS_IPI: evtchn_port_set_pending(ld, lchn->notify_vcpu_id, lchn);