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=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9ABB8C4363C for ; Wed, 7 Oct 2020 10:06:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1346B20870 for ; Wed, 7 Oct 2020 10:06:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="oDbrnmP6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727617AbgJGKGA (ORCPT ); Wed, 7 Oct 2020 06:06:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47348 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727014AbgJGKGA (ORCPT ); Wed, 7 Oct 2020 06:06:00 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C51EC061755; Wed, 7 Oct 2020 03:06:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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; bh=I5Etf9qEHTemyyx/AreDTAuwCMLmW2nSmju3sgma8Yk=; b=oDbrnmP6AupW3Ru7dXb9IEq/lg XSj9zp5GcMzkL3uMSR87apqdlU/zYGzAmUNfF+ESRKast3WvX8AJycao/XC1B/QaWIHQAH/6lF2zn yzHTIfQYnMUyht1oeOh3shHtiJaQeeLCqqXaRP0KaUiplQgP0R5hRYMeUGOmFCVkpnZ1+h+NApqCj BSgHXWGfv1Uxgz2oufRl/Cfq/Q+2uuP6qM2GZ58nOTBLdCklwOz5LaND/RrZrS7kPRoHwAd9Au9/7 VyS5qWhiqA8XakUjQlUIfdBgLEX68lgqgI7gdDtOXVfLo73tZYCbiQ/Syj8JjA/fSquZzWw2mdUs6 RDYNdz9w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQ6KY-00085z-Qk; Wed, 07 Oct 2020 10:05:54 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A77293006D0; Wed, 7 Oct 2020 12:05:51 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6B50F2BA0366F; Wed, 7 Oct 2020 12:05:51 +0200 (CEST) Date: Wed, 7 Oct 2020 12:05:51 +0200 From: Peter Zijlstra To: Sven Schnelle Cc: hca@linux.ibm.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, rafael.j.wysocki@intel.com Subject: Re: [PATCH] s390/idle: Fix suspicious RCU usage Message-ID: <20201007100551.GC2628@hirez.programming.kicks-ass.net> References: <20200908133031.GT1362448@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 07, 2020 at 09:53:25AM +0200, Sven Schnelle wrote: > Hi Peter, > > peterz@infradead.org writes: > > > After commit eb1f00237aca ("lockdep,trace: Expose tracepoints") the > > lock tracepoints are visible to lockdep and RCU-lockdep is finding a > > bunch more RCU violations that were previously hidden. > > > > Switch the idle->seqcount over to using raw_write_*() to avoid the > > lockdep annotation and thus the lock tracepoints. > > > > Reported-by: Guenter Roeck > > Signed-off-by: Peter Zijlstra (Intel) > > [..] > > I'm still seeing the splat below on s390 when irq tracing is enabled: Damn... :/ This one is tricky, trouble seems to be that arch_cpu_idle() is defined to enable interrupts (no doubt because ot x86 :/), but we call it before rcu_exit_idle(). What a mess... let me rummage around the various archs to see what makes most sense here.