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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 861F9C64E7A for ; Tue, 1 Dec 2020 09:13:16 +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 037BD2224C for ; Tue, 1 Dec 2020 09:13:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="A1sDDzFJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 037BD2224C 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.41784.75222 (Exim 4.92) (envelope-from ) id 1kk1iW-0003nZ-Bz; Tue, 01 Dec 2020 09:13:00 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 41784.75222; Tue, 01 Dec 2020 09:13:00 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kk1iW-0003nS-8x; Tue, 01 Dec 2020 09:13:00 +0000 Received: by outflank-mailman (input) for mailman id 41784; Tue, 01 Dec 2020 09:12:58 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kk1iU-0003nN-HS for xen-devel@lists.xenproject.org; Tue, 01 Dec 2020 09:12:58 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 3e3d97f0-72d4-4259-b98e-1ca2637a6a1b; Tue, 01 Dec 2020 09:12:57 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id E4E8CAB7F; Tue, 1 Dec 2020 09:12:56 +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: 3e3d97f0-72d4-4259-b98e-1ca2637a6a1b 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=1606813977; 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=E7Hs6rKppoF5jfW28heEQsAkU1uHWQukzKmDwMlkejA=; b=A1sDDzFJ/FaYBZBpxTvyoXNGxpg2NpLgnQcT2Tc/1/ubygQkoBkyRTb41YSSDJpst2cHVW Iqi7jgYEV5LwTGRWO/WuxjZwrGCTzrPdwP328Jly4ih5gjPCk1KUpXDt+575mYcY6CbkFe IkdXMIrJKyIrxOlYO+8o9c5FpGYyBZU= Subject: Re: [PATCH v2 05/17] xen/cpupool: switch cpupool list to normal list interface To: Juergen Gross Cc: Dario Faggioli , George Dunlap , xen-devel@lists.xenproject.org References: <20201201082128.15239-1-jgross@suse.com> <20201201082128.15239-6-jgross@suse.com> From: Jan Beulich Message-ID: <54301d8c-2d69-3206-6c42-d2638b7e7aa3@suse.com> Date: Tue, 1 Dec 2020 10:12:56 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201201082128.15239-6-jgross@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 01.12.2020 09:21, Juergen Gross wrote: > @@ -260,23 +257,42 @@ static struct cpupool *cpupool_create( > > spin_lock(&cpupool_lock); > > - for_each_cpupool(q) > + if ( poolid != CPUPOOLID_NONE ) > { > - last = (*q)->cpupool_id; > - if ( (poolid != CPUPOOLID_NONE) && (last >= poolid) ) > - break; > + q = __cpupool_find_by_id(poolid, false); > + if ( !q ) > + list_add_tail(&c->list, &cpupool_list); > + else > + { > + list_add_tail(&c->list, &q->list); > + if ( q->cpupool_id == poolid ) > + { > + *perr = -EEXIST; > + goto err; > + } You bail _after_ having added the new entry to the list? > + } > + > + c->cpupool_id = poolid; > } > - if ( *q != NULL ) > + else > { > - if ( (*q)->cpupool_id == poolid ) > + /* Cpupool 0 is created with specified id at boot and never removed. */ > + ASSERT(!list_empty(&cpupool_list)); > + > + q = list_last_entry(&cpupool_list, struct cpupool, list); > + /* In case of wrap search for first free id. */ > + if ( q->cpupool_id == CPUPOOLID_NONE - 1 ) > { > - *perr = -EEXIST; > - goto err; > + list_for_each_entry(q, &cpupool_list, list) > + if ( q->cpupool_id + 1 != list_next_entry(q, list)->cpupool_id ) > + break; > } > - c->next = *q; > + > + list_add(&c->list, &q->list); > + > + c->cpupool_id = q->cpupool_id + 1; What guarantees that you managed to find an unused ID, other than at current CPU speeds it taking too long to create 4 billion pools? Since you're doing this under lock, wouldn't it help anyway to have a global helper variable pointing at the lowest pool followed by an unused ID? Jan