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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 48F1BC433ED for ; Mon, 26 Apr 2021 07:14:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2303060233 for ; Mon, 26 Apr 2021 07:14:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232058AbhDZHOn (ORCPT ); Mon, 26 Apr 2021 03:14:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231616AbhDZHOl (ORCPT ); Mon, 26 Apr 2021 03:14:41 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AC48C061574 for ; Mon, 26 Apr 2021 00:14:00 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1619421236; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=RaeUs5ig8oPGFA8a5hIT5TIvfrrFjhQ7teck4xtX8Qw=; b=PAQJAWrmNnCJFeyQoyRAf1iRckUeWSnfRPOMUwq3jdi0DRw3FiVYyp1J+OgYA5lBjueL5O Ss2I9f8waxo8kC52mPdacLBib7iVIcLXefvU4zIuBtMpYfQYPL/uI9dum1vdn2OmuAEPhq KjPX4zN6uqBHDfFUe1a0wraY/IEXsJDTms+jMOj5Ih1cU4KwKpmfEa3t9zKk5ZE3Fvvn9i 602AfWxkrkdXOZAm8+B6+kypF8cLZc9inS77PagccqQrEuyWi3rMjSNfezgJN9rEhMM5Uf ki+6jVOBNk0xD7O9s57NHE8o4NnkpV2p2cj+Hvt2ZiqiPwKno2wZbG9j9Ka/Jg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1619421236; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=RaeUs5ig8oPGFA8a5hIT5TIvfrrFjhQ7teck4xtX8Qw=; b=WPdHavk1yviViMt0Zq3BEKwkrm0wo6qXWRl+8xsfjDf2f90aI0USk95BIV+qNoN7ck+bUB 4sTfNsPUGW2YrxAg== To: Andi Kleen , "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, john.stultz@linaro.org, sboyd@kernel.org, corbet@lwn.net, Mark.Rutland@arm.com, maz@kernel.org, kernel-team@fb.com, neeraju@codeaurora.org, feng.tang@intel.com, zhengjun.xing@intel.com, Chris Mason Subject: Re: [PATCH v10 clocksource 1/7] clocksource: Provide module parameters to inject delays in watchdog In-Reply-To: <20210426040736.GS1401198@tassilo.jf.intel.com> References: <20210425224540.GA1312438@paulmck-ThinkPad-P17-Gen-1> <20210425224709.1312655-1-paulmck@kernel.org> <20210426040736.GS1401198@tassilo.jf.intel.com> Date: Mon, 26 Apr 2021 09:13:56 +0200 Message-ID: <874kftv7pn.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 25 2021 at 21:07, Andi Kleen wrote: >> occur between the reads of the two clocks. Yes, interrupts are disabled >> across those two reads, but there are no shortage of things that can >> delay interrupts-disabled regions of code ranging from SMI handlers to >> vCPU preemption. It would be good to have some indication as to why > > I assume vCPU preemption here refers to preempt RT? I didn't think > a standard kernel could preempt when interrupt are disabled. Neither does Preempt-RT. It's about vCPU's being preempted by the hypervisor which can happen anytime independent of the state of the guest. Thanks, tglx