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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A87D4C433FE for ; Mon, 29 Nov 2021 18:44:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354629AbhK2Srn (ORCPT ); Mon, 29 Nov 2021 13:47:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379997AbhK2Spg (ORCPT ); Mon, 29 Nov 2021 13:45:36 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6028EC049495 for ; Mon, 29 Nov 2021 06:59:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=SI2iTFkTDzYYUcDOPg4rBs+bvyVyq2R8CsvglYX1/L0=; b=SSRboMwoEA25CeO+Dwu5OjVYSt eCNX6e6DMZ7ALRUuUKw4n0JaJThPQO6j3iAlgZn3Eo4TlaIpid2MdKwK+bILk9g4pjmAzUAkZz7pd Mt1jigQtf0metVpRF+oGQwxWn6bAyiB9814jSinwlGhf5stRQ/JhIvPSiEu9db7BJt/niFYB2hg06 lP1iBLN2yC6TFQAWWcCkkF9VtJFEUUZNLIUG6ypSWiY1zCTFJ9jLfnY8CxwbO7Zs9IbYJNOCxp371 LFAiMyJLZcjDBfRlzMinv30yHCo+mbwdSDzeREhUOuvs4RwQmHE+fiUByQnyMu0p0RtjIJkXLmWBR FPXsWXzw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mri7x-0081dm-Gj; Mon, 29 Nov 2021 14:59:34 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 46CC930023F; Mon, 29 Nov 2021 15:59:32 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2DDEF2B2FCB21; Mon, 29 Nov 2021 15:59:32 +0100 (CET) Date: Mon, 29 Nov 2021 15:59:32 +0100 From: Peter Zijlstra To: Dmitry Vyukov Cc: Hillf Danton , Boqun Feng , syzbot , linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, Alan Stern , Greg Kroah-Hartman , rajatasthana4@gmail.com Subject: Re: [syzbot] INFO: rcu detected stall in newstat Message-ID: References: <0000000000003544c405c8a3026a@google.com> <20211128030309.1897-1-hdanton@sina.com> <20211129131328.1960-1-hdanton@sina.com> 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 Mon, Nov 29, 2021 at 03:15:16PM +0100, Dmitry Vyukov wrote: > Right, I missed the "preempt leak: 00000100 -> 00000101" warning. And > before that there is also "WARNING: inconsistent lock state" warning. > This reminds me of the issues we had with RCU/LOCKDEP before when an > RCU warning disabled LOCKDEP tracking, as the result LOCKDEP missed > part of events (e.g. tracked lock, but missed subsequent unlock) and > due to races/ordering issues it mis-reported them as nonsensical > reports. You're talking about how debug_locks_off() is a hot-racy-mess? That only matters if you're triggering stuff concurrently which *mostly* doesn't happen. I'm also not quite sure how to fix that without globally serializing everything, which would be super unhappy.