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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 06F41C433E0 for ; Mon, 10 Aug 2020 12:11:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC5DA20729 for ; Mon, 10 Aug 2020 12:11:54 +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="qKCWptLl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726789AbgHJMLx (ORCPT ); Mon, 10 Aug 2020 08:11:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726685AbgHJMLs (ORCPT ); Mon, 10 Aug 2020 08:11:48 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FFEAC061756 for ; Mon, 10 Aug 2020 05:11:47 -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=F9rHrTNtavLmJnsON5rguqCFVYnqZxEY92qpddY9gk0=; b=qKCWptLlXNZ9MJYkpyJJTelWEI 5m2ObfMuiBrbwk0iCOwK1wo5W8d9X7IVR9elMzSK9VjTwAm9fZDiSSID/U+80YPpHD8/tug3lYBKT 5HZI7R2RErVfAb+H+ItQI1myQGDAoz2d0V2zbCbVIi8uNiXHK423yD4CgHSk4nPR+GK7TNzMd1HB3 NI4oSuWf6QwvUcsUnW4Ou4wARxtxN7JXPGIdtaDRtgnlpnuY1XCeWqVU3IxQ2Wav944f3OogxL3Vh 4mWnZtWyDh1r3qMes4bX7sUK5KNcMw9A2H8menQJy4Hl14++m+11TwewW/HPqMG/wnI/0pnYxA9vn JiqFxHxA==; 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 1k56eS-00005f-5C; Mon, 10 Aug 2020 12:11:40 +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 CFE8230015A; Mon, 10 Aug 2020 14:11:38 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 88AF52B2C8031; Mon, 10 Aug 2020 14:11:38 +0200 (CEST) Date: Mon, 10 Aug 2020 14:11:38 +0200 From: peterz@infradead.org To: Marco Elver Cc: tglx@linutronix.de, mingo@kernel.org, will@kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, paulmck@kernel.org, rostedt@goodmis.org, rjw@rjwysocki.net Subject: Re: [RFC][PATCH 0/3] Tracing, Idle, RCU and such goodness Message-ID: <20200810121138.GV2674@hirez.programming.kicks-ass.net> References: <20200807192336.405068898@infradead.org> <20200810095535.GA1597985@elver.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200810095535.GA1597985@elver.google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 10, 2020 at 11:55:35AM +0200, Marco Elver wrote: > Unfortunately I get LOCKDEP_DEBUG warnings, when testing with one of > syzbot's configs. This appears at some point during boot (no other > test): > > DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled()) > WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:4875 check_flags+0x52/0x200 kernel/locking/lockdep.c:4875 > Modules linked in: > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.8.0+ #8 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 > RIP: 0010:check_flags+0x52/0x200 kernel/locking/lockdep.c:4875 > Code: c0 74 48 e8 40 f7 a5 03 85 c0 74 20 83 3d bd 33 53 05 00 75 17 48 c7 c7 ce 12 c9 85 48 c7 c6 04 8c ca 85 31 c0 e8 4e c1 f7 ff <0f> 0b 48 c7 c7 db 8b ca 85 e9 8c 01 00 00 85 c0 75 0f 65 8b 05 c5 > RSP: 0000:ffffffff86203bf0 EFLAGS: 00010046 > RAX: 1f9fa70771052a00 RBX: 0000000000000000 RCX: ffffffff8627e980 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 > RBP: 0000000000000000 R08: ffffffff813d8494 R09: 0000000000000000 > R10: 0000000000000012 R11: ffffffff8627e980 R12: ffffffff8627e980 > R13: ffffffff862e3420 R14: 00000000ffffffff R15: 0000000000000046 > FS: 0000000000000000(0000) GS:ffff88881fa00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff88883ffff000 CR3: 0000000006275001 CR4: 0000000000770ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > PKRU: 00000000 > Call Trace: > lock_is_held_type+0x4d/0x110 kernel/locking/lockdep.c:5043 > lock_is_held include/linux/lockdep.h:266 [inline] > rcu_read_lock_sched_held+0x41/0x90 kernel/rcu/update.c:136 > trace_lock_acquire+0x49/0x120 include/trace/events/lock.h:13 > lock_acquire+0x8d/0x2c0 kernel/locking/lockdep.c:5003 > mutex_trylock+0xdd/0x120 kernel/locking/mutex.c:1420 *groan*, indeed! Which is the direct result of lockdep recursion because we pulled that tracepoint out from under the recursion thing. Let me go prod this with a sharp stick...