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 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 CB8BBC433DB for ; Tue, 5 Jan 2021 13:24:58 +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 9165522AAC for ; Tue, 5 Jan 2021 13:24:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9165522AAC 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.61977.109389 (Exim 4.92) (envelope-from ) id 1kwmKR-0002kd-0l; Tue, 05 Jan 2021 13:24:51 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 61977.109389; Tue, 05 Jan 2021 13:24:50 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kwmKQ-0002kW-T9; Tue, 05 Jan 2021 13:24:50 +0000 Received: by outflank-mailman (input) for mailman id 61977; Tue, 05 Jan 2021 13:24:50 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kwmKP-0002kP-Vr for xen-devel@lists.xenproject.org; Tue, 05 Jan 2021 13:24:50 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 0704df83-847e-42cb-abba-053eae35ca80; Tue, 05 Jan 2021 13:24:49 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6D721AD0B; Tue, 5 Jan 2021 13:24:48 +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: 0704df83-847e-42cb-abba-053eae35ca80 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=1609853088; 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=Xzf3n34RjXIRdOX5kcsS30euTM1Kzp9AmLREhagMPnY=; b=UC4DE6r/L66Umi5ReNzfi3OZwxzn9cC5AyVQtiySy7glCynG7ryWXmOcMKbq08s5hLeLRb g29rNB7s0BdxSbDQxkug35FIghUax9lImMkKVIH/naZAKup5+F1gk5S6NoUcbubHVXdDoU LC7Paj4qDF1/UX9v2MHCDktMlvBWR00= Subject: [PATCH 2/5] evtchn: don't pointlessly use get_domain() From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini , Wei Liu References: <3f069a0e-39a9-f5c8-154e-ac41e8b2a1c8@suse.com> Message-ID: <1f9448ac-7889-3cfb-e136-d8c37f63279c@suse.com> Date: Tue, 5 Jan 2021 14:24:48 +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: <3f069a0e-39a9-f5c8-154e-ac41e8b2a1c8@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit For short-lived references rcu_lock_domain() is the better (slightly cheaper) alternative. Signed-off-by: Jan Beulich --- a/xen/common/event_channel.c +++ b/xen/common/event_channel.c @@ -642,7 +642,7 @@ int evtchn_close(struct domain *d1, int */ write_unlock(&chn1->lock); write_unlock(&chn2->lock); - put_domain(d2); + rcu_unlock_domain(d2); chn2 = NULL; } @@ -677,7 +677,7 @@ int evtchn_close(struct domain *d1, int */ write_unlock(&chn1->lock); write_unlock(&chn2->lock); - put_domain(d2); + rcu_unlock_domain(d2); chn2 = NULL; } @@ -725,9 +725,8 @@ int evtchn_close(struct domain *d1, int if ( !chn2 ) { - /* If we unlock chn1 then we could lose d2. Must get a reference. */ - if ( unlikely(!get_domain(d2)) ) - BUG(); + /* If we unlock chn1 then we could lose d2. */ + rcu_lock_domain(d2); chn2 = _evtchn_from_port(d2, chn1->u.interdomain.remote_port); BUG_ON(!chn2); @@ -778,7 +777,7 @@ int evtchn_close(struct domain *d1, int */ write_unlock(&chn1->lock); write_unlock(&chn2->lock); - put_domain(d2); + rcu_unlock_domain(d2); } write_unlock(&d1->event_lock);