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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 2ABFAFA3735 for ; Thu, 17 Oct 2019 16:25:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EF8F22089C for ; Thu, 17 Oct 2019 16:24:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="SFBW3KU2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2502377AbfJQQY6 (ORCPT ); Thu, 17 Oct 2019 12:24:58 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:47640 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389405AbfJQQY6 (ORCPT ); Thu, 17 Oct 2019 12:24:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=tM11n8HxbnKWuIhVBFZir6ZW0eaOohaPCZqy9IypX4U=; b=SFBW3KU2AFnuPudmAUQJa1JCr lzNCY42eqxDiR5TpNp5EuDL8nzHiMAQ48K5MeYMzAxKbrGFWSDWMk8nwju4mlbJTvAvLQ+hE0IPXH wW6N08roi74hu6tGILnTfvmhDThfE55UeyADHlEOntoNPWirpMlWavoCHICueEnFAG6sWhJHWx6Cw cj9RGPjUb8JTHrccwaeYX3JtE/Coju00bGauyGPykagxvMPlG/cOuiXRXQgzh8FX1h6VHS30t6Ngq ImVcFe7rnAxwd9JQj8INAsbLw+PQP10U7atjrXkNsLllu8GjFi9/4yAo5AkcuQoqV7hKkcB7BrxLW vMka7sSwA==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iL8a5-0005qh-Mk; Thu, 17 Oct 2019 16:24:53 +0000 Date: Thu, 17 Oct 2019 09:24:53 -0700 From: Christoph Hellwig To: Robin Murphy Cc: joro@8bytes.org, iommu@lists.linux-foundation.org, maz@kernel.org, julien.grall@arm.com, linux-kernel@vger.kernel.org, Qian Cai Subject: Re: [PATCH] iommu/dma: Relax locking in iommu_dma_prepare_msi() Message-ID: <20191017162453.GA6012@infradead.org> References: <5af5e77102ca52576cb96816f0abcf6398820055.1571245656.git.robin.murphy@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5af5e77102ca52576cb96816f0abcf6398820055.1571245656.git.robin.murphy@arm.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 16, 2019 at 06:07:36PM +0100, Robin Murphy wrote: > @@ -1180,7 +1179,7 @@ int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr) > struct iommu_domain *domain = iommu_get_domain_for_dev(dev); > struct iommu_dma_cookie *cookie; > struct iommu_dma_msi_page *msi_page; > - unsigned long flags; > + static DEFINE_MUTEX(msi_prepare_lock); Just a style nitpick, but I find locks declared inside functions really weird. In addition to that locks not embedded into a structure and not directly next to variables or data structures they protect really need a comment explaining what they are trying to serialize.