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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=unavailable 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 9B262C282CE for ; Tue, 4 Jun 2019 13:49:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F76623CEB for ; Tue, 4 Jun 2019 13:49:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727312AbfFDNtG (ORCPT ); Tue, 4 Jun 2019 09:49:06 -0400 Received: from foss.arm.com ([217.140.101.70]:44428 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727033AbfFDNtG (ORCPT ); Tue, 4 Jun 2019 09:49:06 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 46D20341; Tue, 4 Jun 2019 06:49:06 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 790F53F690; Tue, 4 Jun 2019 06:49:04 -0700 (PDT) Date: Tue, 4 Jun 2019 14:49:01 +0100 From: Catalin Marinas To: Julien Grall Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tglx@linutronix.de, rostedt@goodmis.org, bigeasy@linutronix.de, suzuki.poulose@arm.com, will.deacon@arm.com, dave.martin@arm.com Subject: Re: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs() Message-ID: <20190604134901.GE6610@arrakis.emea.arm.com> References: <20190530113058.1988-1-julien.grall@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190530113058.1988-1-julien.grall@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On Thu, May 30, 2019 at 12:30:58PM +0100, Julien Grall wrote: > cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable > callback. A spin lock is used to ensure the hook is registered before > the rest of the callback is executed. > > On -RT spin_lock() may sleep. However, all the callees in stop_machine() > are expected to not sleep. Therefore a raw_spin_lock() is required here. > > Given this is already done under stop_machine() and the work done under > the lock is quite small, the latency should not increase too much. > > Signed-off-by: Julien Grall Queued for 5.3. Thanks. -- Catalin