Received: by 2002:ac0:946b:0:0:0:0:0 with SMTP id j40csp4042436imj; Tue, 12 Feb 2019 08:50:50 -0800 (PST) X-Google-Smtp-Source: AHgI3IZuI3M1Cv9rWvwLj8AwfgNzMacVROTyGKRNKgudJvAoNzP3H46Xvf2vcBKqreMbqaxPrrRm X-Received: by 2002:aa7:8249:: with SMTP id e9mr4808188pfn.93.1549990250142; Tue, 12 Feb 2019 08:50:50 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1549990250; cv=none; d=google.com; s=arc-20160816; b=0KsnbmlbLsYMFQhFQx26Pv1MVnqZlleCSeDZfK11H0WN3JlmZhQYE0U1h/x8jn0DhE HES5ASeM5PbXFpKBF1FvhvoQk1xEnruUey5luG9ajTudOP+KJeb3WZtohhgtCBFMo1Av Wl9tOdG0AMrR3IlzvXgBbsO6kC9eRoQA8540wHl2nWNzxJglkONWCXR/bT8OmHFVCLHU /JaZHabQrS5BQroUWxvq5TsEsafi8p6xPIrlRsukmKP+91SlgUMsYQ/YZyMPdulz3wjI oOCuFbS9DJ2haNkrUeDgBqvgaOEpY0lbSikHVj6Y/2T94Lr2yiHKe5SEe3v6gdzz5Wbl ilTA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:feedback-id:mime-version:user-agent :references:message-id:in-reply-to:subject:cc:to:from:date :dkim-signature; bh=d9wM12jhuDTWdWt+Pkovf6I5uVUhrDCPMcwRg2iB6/c=; b=RwGy9evWSOlkj5C2qEilSkpUGgHdEyR+K4IuW0TB+N21l3aiLVs8yArJ/CDCd1PB1s 0pvlpaFZkhHdmc1DY2aTw9Sw0U8Q6vG+Dk0q1QrqehJQnL8I4pgaoQ1IfP1nx6UQBcKq FI8H7d29qKUdAvADUAnULHtKkDFWhK7k4+suugbZMGbe1APaqCHDxuooQwSHs6MjFAK7 xqOEHuj3eeBsrVMLUWSuiZC7ABbNJJaPG+mW62GyIPlJKbXyN325WSDgl3E9FloW3IkJ SR6+hXU/OOcQ4Q/ZWLpu/DAi+JJM1V9Z2TKgsnN2S6eF8rApa96HcPvRG9fATfPAHAWk Z3JQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@amazonses.com header.s=ug7nbtf4gccmlpwj322ax3p6ow6yfsug header.b=dPwog4Db; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id t4si12259162pga.83.2019.02.12.08.50.33; Tue, 12 Feb 2019 08:50:50 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@amazonses.com header.s=ug7nbtf4gccmlpwj322ax3p6ow6yfsug header.b=dPwog4Db; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731239AbfBLQuN (ORCPT + 99 others); Tue, 12 Feb 2019 11:50:13 -0500 Received: from a9-35.smtp-out.amazonses.com ([54.240.9.35]:55606 "EHLO a9-35.smtp-out.amazonses.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729078AbfBLQuM (ORCPT ); Tue, 12 Feb 2019 11:50:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=ug7nbtf4gccmlpwj322ax3p6ow6yfsug; d=amazonses.com; t=1549990211; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type:Feedback-ID; bh=d9wM12jhuDTWdWt+Pkovf6I5uVUhrDCPMcwRg2iB6/c=; b=dPwog4Db8cxWFTs8RaPbWPHsdjVXXzK6xqpC2es8j1a9vMwSTJTBbxIqClS4bTWi jn3E5648vwwyFuDLlzLP3ebtNmQ8QHcaanGSqOxZWOF9WwuscWPvVRcezYZjIzwFHH3 zSJ0zA/tay7p90Jbs8Pdv9fCw9l9ZFY8VqBAPqsw= Date: Tue, 12 Feb 2019 16:50:11 +0000 From: Christopher Lameter X-X-Sender: cl@nuc-kabylake To: Alexey Kardashevskiy cc: Daniel Jordan , jgg@ziepe.ca, akpm@linux-foundation.org, dave@stgolabs.net, jack@suse.cz, linux-mm@kvack.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org, alex.williamson@redhat.com, paulus@ozlabs.org, benh@kernel.crashing.org, mpe@ellerman.id.au, hao.wu@intel.com, atull@kernel.org, mdf@kernel.org Subject: Re: [PATCH 2/5] vfio/spapr_tce: use pinned_vm instead of locked_vm to account pinned pages In-Reply-To: Message-ID: <01000168e29daf0a-cb3a9394-e3dd-4d88-ad3c-31df1f9ec052-000000@email.amazonses.com> References: <20190211224437.25267-1-daniel.m.jordan@oracle.com> <20190211224437.25267-3-daniel.m.jordan@oracle.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SES-Outgoing: 2019.02.12-54.240.9.35 Feedback-ID: 1.us-east-1.fQZZZ0Xtj2+TD7V5apTT/NrT6QKuPgzCT/IC7XYgDKI=:AmazonSES Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 Feb 2019, Alexey Kardashevskiy wrote: > Now it is 3 independent accesses (actually 4 but the last one is > diagnostic) with no locking around them. Why do not we need a lock > anymore precisely? Thanks, Updating a regular counter is racy and requires a lock. It was converted to be an atomic which can be incremented without a race.